Orals: Thu, 1 May | Room D1
Seismic microzonation is essential for urban planning and earthquake risk mitigation by delineating areas with varying seismic hazards. In 2009, a comprehensive microzonation map was developed for the canton of Basel-Stadt and parts of Basel-Landschaft and Solothurn. This map supported the Swiss standard SIA 261 by identifying site-specific earthquake hazards. Since then, new geophysical, geotechnical, and seismological datasets have been collected within various projects, and advancements in data analysis methods have been made. Together with the updates to the SIA 261 standard (2020) and the national seismic hazard model (Wiemer et al., 2016), this necessitates a revision of the 2009 microzonation.
To support this revision and refine the understanding of local seismic response, we complement the existing dataset with new single-station ambient vibration measurements and deployment of temporary seismic stations (to evaluate seismic amplification in the areas of interest) and utilize advanced methodologies to analyze geophysical and seismological data.
All available single-station geophysical data allow for resolving the areas with variable subsurface structure and properties. In particular, this data is used to retrieve the horizontal-to-vertical spectral ratio (HVSR) and fundamental frequencies of resonance (f0) across the study area. Additionally, the HVSR and f0 are used for cluster analysis to support the definition of the boundaries between microzones for revised microzonation maps.
The data recorded by the network of existing and previously available seismic stations and six new temporary stations are used to obtain refined estimates of empirical amplification functions (EAFs) using Empirical Spectral Modeling (ESM, Edwards et al. 2013) and Standard Spectral Ratio (SSR, Borcherdt, 1970) methods. These EAFs are also used to validate the 2009 amplification models (Shynkarenko et al. 2024) and cross-check fundamental resonance frequencies retrieved from the HVSR. To retrieve ground motion amplification in regions lacking seismic station observations, the Canonical Correlation method will be applied to HVSR data (Panzera et al., 2021; Imtiaz et al., 2024).
The outcomes of this study will allow for the integration of ground motion amplification data with seismic hazard models on rock and updating uniform hazard spectra, thus enhancing the microzonation's contribution to risk mitigation and urban planning.
References:
Borcherdt, R.D. (1970). Effects of local geology on ground motion near San Francisco Bay, Bull. Seismol. Soc. Am. 60(1), 29-61.
Edwards, B., Michel, C., Poggi, V., Fäh, D. (2013). Determination of site amplification from regional seismicity: application to the Swiss National seismic Networks, Seismol. Res. Lett. 84(4), 611-621.
Wiemer, S. et al. (2016). Seismic Hazard Model 2015 for Switzerland (SUIhaz2015), http://www.seismo.ethz.ch/export/sites/sedsite/knowledge/.galleries/pdf_knowledge/SUIhaz2015_final-report_16072016_2.pdf_2063069299.pdf.
Panzera, F., Bergamo, P., Fäh, D. (2021). Canonical correlation analysis based on site-response proxies to predict site-specific amplification functions in Switzerland, Bull. Seismol. Soc. Am. 111(4), 1905‑1920.
Imtiaz, A., Panzera, F., Fäh, D. (2024). Performance of canonical correlation in developing a high-resolution site amplification map in Basel. Proceedings of the 18th World Conference on Earthquake Engineering (18WCEE), 9 pages, Milan, Italy.
Shynkarenko, A., Bergamo, P. Imtiaz, A., Chieppa, D., Fäh, D. (2024). Report on the Common Task 1 of Basel Landschaft and Basel Stadt Microzonation Project: Verification of the amplification functions used in 2009, Report, Swiss Seismological Service.
How to cite: Shynkarenko, A., Imtiaz, A., Bergamo, P., and Fäh, D.: Single-station geophysical and seismological investigations towards revising seismic microzonation of the Basel region, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2900, https://doi.org/10.5194/egusphere-egu25-2900, 2025.
There has been extensive discussion as to whether the scope of site classification II is too broad in current Chinese seismic code. To address this issue, this study aims to optimize the site classification scheme for Chinese seismic code using clustering analysis of site amplification. Firstly, we estimate the empirical site amplification factors of KiK-net stations by the residual analysis method, and classify them by the site classification scheme of Chinese seismic code. Next, we perform k-means clustering analysis on the stations of site class II, considering site amplification factors, equivalent shear wave velocities and thicknesses of sedimentary layers as explanatory variables, and obtain two clusters with distinct site amplification effects. Finally, we use correlation analysis and Receiver Operating Characteristic (ROC) curve to guide the optimization of site classification scheme, and suggest dividing site class II into two subclasses, IIa and IIb, by a threshold of 15m for the thickness of sedimentary layer. The proposed optimized classification scheme would be beneficial for improving the seismic design code and could be further applied to the development of ground motion models and seismic hazard analysis.
How to cite: Liu, Y., Ren, Y., Wen, R., and Wang, H.: An optimization suggestion for site classification scheme in Chinese seismic code based on clustering analysis of site amplification, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5907, https://doi.org/10.5194/egusphere-egu25-5907, 2025.
Understanding site response is important for assessing seismic hazards. We present methods — Time-Frequency Resonance Analysis (TFRA) and the Envelope of the Power Spectrum of Displacement to Jerk (EPSDJ) for analyzing both linear and nonlinear site responses. These techniques require only a single surface station with weak to strong motion records, eliminating the need for a reference site. While they do not provide site amplification values, they effectively identify broadband site resonances and nonlinear site behavior.
The methods are first applied to seismic data from KiK-net, Japan, with borehole responses serving as a benchmark. We then extend the analysis to southeastern Türkiye, comparing results with Horizontal-to-Vertical Spectral Ratio (HVSR) and Generalized Inversion Technique (GIT) methods to identify the most effective combination for site response assessment in the region. After validation in regions with reference data, the method is applied to seismic records from the Taiwanese seismic network across diverse geological settings.
The results highlight the complexity of site response, with linear and nonlinear behaviors varying across frequency bands and regions. We observe that local geology significantly influences the ground motion, controlling the seismic hazard and its uncertainty over a broadband frequency range. The evaluation includes nonlinear behavior in the regions of interest, identifying stations that are more susceptible to nonlinearity, and quantifying both local and regional levels of nonlinear site response. Additionally, the findings indicate that nonlinearity can manifest during weak motion (< 30 cm/s2), a behavior observed consistently across all regions studied.
How to cite: Lai, S.-T., Schibuola, A., Bonilla, L. F., Bindi, D., Loviknes, K., Lin, C.-M., and Cotton, F.: Linear and Nonlinear Site Response Evaluation Using Single-Station Time-Frequency Analysis: Applications Across Regions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6523, https://doi.org/10.5194/egusphere-egu25-6523, 2025.
Seismic site characterization is the process of categorizing a site based on the dynamic properties of the soil deposit at the site and is vital for understanding site-specific seismic behaviour as well as mitigating earthquake hazards. The current study focuses on the Ganderbal district in the seismically active Kashmir Himalayas, employing Multichannel Analysis of Surface Waves (MASW) and Microtremor Horizontal-to-Vertical Spectral Ratio (MHVSR) techniques to determine essential dynamic soil parameters viz., time-averaged shear wave velocity (Vs30) and peak HVSR frequencies respectively. The geophysical tests were performed at about 35 sites in the main town area of the district, covering major landforms and geological deposits. The results facilitated the determination of seismic site classes at the testing locations using the methodology established by Zahoor et al. (2023) for the Kashmir Valley. This classification system, adapted from Di Alessandro et al. (2012), incorporates peak H/V amplitudes and frequencies, the HVSR curve shape, and Vs30 as proxies for site amplification. Field experimental data, combined with topographical and geological information, identified four distinct zones in the study area showing distinct site response namely, Zone A, characterized by alluvial deposits from the Sind and Jhelum rivers; Zone B, consisting of the Karewa highlands; Zone C, comprising marshy lands; and Zone D, representing hilly terrains. Vs30 estimates from MASW testing revealed varying stiffness in the zones, with average values of ~210 m/s in Zone A, ~400 m/s in Zone B, ~100 m/s in Zone C, and ~516 m/s in Zone D. H/V amplitude as high as 6.0-15.0 at frequencies of 1.0-5.0 Hz were obtained in Zone A, indicating significant impedance contrast within the deposit or trapping of seismic waves. Zone B showed peaks with H/V amplitude 2.0-3.0 at frequencies < 1 Hz indicating deep sedimentary depth, along with secondary peaks at higher frequencies signifying a multi-layered subsurface. Zone C on the other hand exhibited clear peaks in the range of 1.0-3.0 Hz with H/V amplitude of 6.0-11.0. and smaller peaks at higher frequencies (>10 Hz). In Zone D, broadband peaks in HVSR curves were attained, implying complexity of subsurface conditions, probably due to lateral variations or sloping underground layers. Using the computed values of these amplification proxies, seismic site characterisation for the study area was conducted. The results align closely with the geology and topography of the area and demonstrate a clear connection to factors such as proximity to rivers. This study offers insights into the seismic behavior of soils in the Ganderbal district, aiming to support seismic microzonation and risk assessment efforts in the region. The results will contribute to the understanding of local site effects in the region, such as ground motion amplification and the potential for seismic hazards like liquefaction and landslides. Given the critical seismotectonic setting of the Himalayas, the findings are crucial for informing town planning and enhancing disaster risk reduction initiatives in the area.
How to cite: Zahoor, F. and Raina, B. A.: Seismic Site Characterization of the Ganderbal District, Kashmir Valley, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7779, https://doi.org/10.5194/egusphere-egu25-7779, 2025.
A strong earthquake of magnitude (MS) 6.8 has struck Luding county in Sichuan province, southwestern China, on 5 September 2022 at 04:52:18 UTC. The Luding Earthquake occurred at the junction of the eastern edge of the Qinghai-Tibet Plateau and the Sichuan Basin. The affected area features highly rugged terrain with an elevation difference of nearly 7 km, providing an opportunity to study the topographic effects on seismic ground motion. In this study, a flat surface model (3DFlat model) and a model incorporating surface topography (3DTopo model) were developed. The low-frequency part of the ground motion is simulated using a curvilinear grid finite difference method, while the high-frequency part is simulated using a three-component stochastic finite fault model. The low- and high-frequency results are combined to synthesize broadband ground motion.
The results show that the scattering effects caused by the dramatic topographic relief complicate the wavefields of the 3DTopo model and the overall match with the waveform and spectral characteristics of the observation records. The 3DTopo model has a richer high-frequency component compared to the 3DFlat model, while the ground motion below 0.1 Hz is not affected by surface topography. Comparing the 3DFlat and 3DTopo models reveals that the multiple scattering effects of seismic waves caused by ridge and canyon topography result in irregular wavefront shapes, with numerous scattered and reflected waves in the velocity waveforms. The distribution of the peak parameters ln(δPGA) and ln(δPGV) shows significant correlations with surface topography. The distribution of amplification (attenuation) of ground motion corresponds to the orientation of mountain ridges and valleys. Ground motion is significantly amplified at wave crests and ridges (ln(δPGA) > 0), with the amplification of PGA and PGV reaching up to 5.4 times and 3.6 times, respectively. In contrast, ground motion is significantly attenuated in valleys (ln(δPGA) < 0), with PGA and PGV reduced by up to 0.40 times and 0.45 times, respectively. Our further research on the relationship between ground motion and topographic features establishes a correlation between the topographic amplification factor AFTOPO and the Relief Degree of Land Surface (RDLS).
In addition, we also used a frequency-domain matching technique to combine low- and high-frequency results into broadband ground motion. Comparisons with observed records and four NGA-West2 ground motion models (ASK14, BSSA14, CB14, and CY14) show that, although the residuals of ground motion parameters (PGV, PGA, PSA) obtained by different methods fluctuate with the period. This study will be an important to promote the incorporation of topographic effects into seismic zoning.
How to cite: Qiang, S., Wang, H., Wen, R., and Ren, Y.: Ground-Motion Simulation and Surface Topography Effects of the 2022 MS 6.8 Luding, Southwest China, Earthquake, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7894, https://doi.org/10.5194/egusphere-egu25-7894, 2025.
The S-wave Fourier amplitude spectra from a total of 3232 ground-motion acceleration recordings obtained at 254 strong-motion stations during 400 earthquakes in seven regions (western Tianshan, northern Ningxia, Tianjin-Tangshan, Longmenshan fault region, northeastern Yunnan-southeastern Sichuan, northwestern Yunnan, and southeastern Yunnan) of China were selected and adopted for the spectral decomposition to separate simultaneously the path attenuation, source spectra, and site responses. The non-parametric path attenuation curves were empirically represented by the trilinear geometrical spreading model and the frequency-dependent anelastic attenuation expressed as the function of quality factor. The regional dependency of path attenuation was further discussed. The inverted source spectral were used to estimate the seismic moments, corner frequencies, and also stress drops based on the theoretical ω-2 source model. The stress drops mainly varies in a range of 0.1-10 MPa. We discussed the dependence of stress drop both on region and on the type of fault. The spatiotemporal changes in stress drop values were further investigated to reveal the seismic self-similarity and seismic mechanism. The site responses at 211 stations were used to evaluate the effects of the local site conditions (e.g., VS30, site class defined by Seismic Design Code for Buildings of China). We developed the empirical models for site responses related to either site class or VS30. The regional-dependence of site response was also discussed in this study, and furthermore, empirical site responses for the same site class were suggested for various study regions. The comprehensive understanding on the path attenuation, source parameters, and site effects will play an important role on the reliable predictions on ground motions, especially considering their regional dependency.
How to cite: Wang, H., Li, H., Ren, Y., and Wen, R.: Source parameters, path attenuation, and local site effects in China derived from the ground-motion spectral inversion analyses, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8321, https://doi.org/10.5194/egusphere-egu25-8321, 2025.
Deeply incised valleys or sedimentary basins often exhibit complex resonance patterns that diverge from the commonly assumed one-dimensional (1D) behaviour. In such cases, the soil resonance fundamental frequency f0 is not determined by the local depth-to-bedrock; instead, f0 is constant across the central portion of the basin section, reflecting the overall geometry and material properties of the sedimentary infill. These 2D (or even 3D) resonance regimes are challenging to identify and are generally overlooked in building codes. This study, funded by the Swiss Federal Office for the Environment, seeks to characterize 2D resonance phenomena across Switzerland by leveraging over 6000 ambient noise measurements and a large-scale morphometric dataset.
The primary dataset comprises ~4000 ambient vibration measurements acquired across Switzerland since the late 1990s, archived in the Swiss Seismological Service (SED) site characterization database. The recordings were processed using the horizontal-to-vertical spectral ratio (H/V) technique and soil resonance frequencies were identified following the best practice criteria. This database has been further enhanced by recent high-resolution ambient noise campaigns conducted by SED in key sedimentary basins: the Swiss Rhône Valley, the Lucerne and Horw basins in Central Switzerland, and the High Rhine Valley near Basel. These campaigns, with spatial resolutions ranging from 100 to 400 m, contribute approximately 2000 additional measurements with their f0 for the areas of interest.
This sizeable ambient noise database is paired with a collation of various geological/geophysical models: the backbone model by the Swiss Federal Office of Topography is complemented by regional models for the Alpine and High Rhine valleys, the Geneva Basin, the Grisons, and the Basel area. The collation of such models maps the depth of the sediments-to-bedrock interface over most of Switzerland. Based on this information, we performed morphometric analyses, which allowed extracting key geometrical parameters (shape, width, maximum depth) of the sedimentary infill along 4500 transects – spaced by 250 m and spanning all large sedimentary basins.
Cross-referencing the soil resonance frequencies with the morphometric characteristics of the sedimentary basins, we observed patterns consistent with those predicted by numerical studies from the literature. Our analysis distinguishes valleys with 1D resonance behaviour from those with 2D resonance regimes. Furthermore, as a valley's shape ratio (half-width over maximum depth) increases, resonance frequencies converge towards specific 2D vibration modes, particularly fundamental SH- and SV-modes and their higher harmonics. We also examined whether these ambient vibration resonance modes reflect into the (directional) ground motion local response at seismic stations.
The results of this study are synthesized into a national-scale map identifying basins and valley bottoms with 1D or 2D resonance behaviours and their corresponding resonance frequencies. Our study will contribute to the decision of whether the Swiss national building code should adopt tailored elastic response spectra for alpine valleys prone to 2D resonance patterns.
How to cite: Glueer, F., Bergamo, P., Shynkarenko, A., Imtiaz, A., Janusz, P., Borgeat, X., Panzera, F., and Fäh, D.: Combining a large, nationwide ambient noise database with morphometric analyses to map 2D resonance effects in sedimentary basins in Switzerland, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8588, https://doi.org/10.5194/egusphere-egu25-8588, 2025.
The 2016 Central Italy earthquakes had a strong impact in the town of Norcia, which was already hit by a strong earthquake in 1997. The proximity to the seismogenic fault and the damages to buildings have highlighted the need of in-depth studies of the site effects in the Norcia area.
This work presents preliminary results on the ground response and Soil-Structure Interaction of a reinforced concrete school building in Norcia.
The site response analysis is based on a newly developed 2D subsurface model of the area, constructed using original geological and geophysical data specifically acquired for this research. The model is integrated with the seismic section located near the school, and incorporates detailed stratigraphic information to improve site-specific accuracy.
The Norcia School is monitored by the Structural Observatory of the Italian Department of Civil Protection, providing a unique dataset of seismic recordings, both prior to the 2016 earthquake sequence and during the major seismic events of August and October 2016. The integration of the newly constructed 2D subsurface model significantly enhances the understanding of the local site effects and their influence on the soil-structure interaction.
The outcomes of the soil model are compared with those recorded at the free field station of the school, and a dynamic identification of the structure is carried out, allowing to infer the natural vibration frequencies of the structure. Preliminary results of a numerical model of the structure including SSI will be presented.
The findings of this research could have important implications for technical building codes and seismic design standards, which currently assume a rigid soil-foundation interface in structural assessments. By demonstrating the impact of soil-structure interaction on seismic response, this study emphasizes the need to update construction regulations to account for site-specific geotechnical conditions. Such updates could lead to safer, more resilient designs, particularly for critical structures located in near-fault or geologically complex areas.
How to cite: Giallini, S., Fiorentino, G., Pagliaroli, A., Caciolli, M. C., and Mancini, M.: The role of site effects and soil-structure interaction phenomena on the seismic response of a school building in Norcia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9093, https://doi.org/10.5194/egusphere-egu25-9093, 2025.
The role of 2-D and 3-D geometry in the seismic response of alluvial valleys and sedimentary basins can be evidenced by physics-based numerical simulations of seismic wave propagation in heterogeneous media. The present work focuses on the 5 km wide valley on the northern shore of Lake Garda in the Italian Alps. A recent study carried out in this area has shown that amplifications of earthquake ground motion up to 10 in the frequency range of engineering interest (0.5-10 Hz) are possible at sites inside the valley in respect to a rock site. To understand the origin of the observed site response, which 1D stratigraphic effects alone cannot explain, we used the available geological and geophysical data and built a 3D digital structural-geophysical model. The used data consist of seismic reflection profiles, interpreted geological sections and borehole measurements from existing literature, as well as data from newly conducted measurement campaigns of microtremors, shear wave velocity profiles and gravity. In the present work, we demonstrate the efficiency of the resulting 3D model in simulating the ground motion variability by a quantitative comparison between the empirical and the numerically evaluated amplification functions at a number of sites. In particular, we consider the amplification functions evaluated from earthquake ground motion recordings at 19 sites, where a temporary seismological network operated between 2019 and 2021. We evaluate the numerical amplification functions from physics-based numerical simulations of vertically emerging plane waves in the digital 3-D model. In order to perform the numerical simulations we used the 3-D spectral-element and frequency-wave number hybrid method, that is implemented in the latest versions of the open-source software SPECFEM3D Cartesian. The study confirms that the area is susceptible to combined 1D to 3D site effects generated by the peculiar geometry of the deposits composing the basin. The validated 3D model could provide a basis for the calculation of earthquake scenarios in the area.
How to cite: Klin, P., Primofiore, I., Zampa, L., Garbin, M., Viganò, A., Barnaba, C., Palmieri, F., and Laurenzano, G.: The alluvial plain on the northern shore of Lake Garda (Italy) as a case study for physics-based numerical simulations of site effects., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9536, https://doi.org/10.5194/egusphere-egu25-9536, 2025.
The Grenoble basin, located in the French Alps, is a region of significant interest for seismic hazard assessment due to its thick sedimentary layers and surrounding high massifs, leading to 2D/3D complex wave propagation patterns. With the aim to develop suitable strategies for seismic microzonation in alpine valleys, this study focuses on the seismic response of the basin using state-of-the-art 3D simulations performed with the EFISPEC3D spectral element method code for frequencies up to 5 Hz. These simulations aim to capture the intricate interactions between geological features, including lateral heterogeneity and basin geometry, which are not considered in traditional 1D microzonation approaches.
A primary goal of this research is to compare synthetic seismic data derived from 1D and 3D models with observed data to identify the limitations of 1D approach to provide a robust estimation of the site effects. Particular attention is paid to the analysis of fundamental frequencies and seismic wave amplification. While central regions of the basin exhibit consistent fundamental frequencies across 1D and 3D models, discrepancies arise at the edges due to the presence of complex lateral heterogeneities.
The study further investigates aggravation factors such as Peak Ground Velocity (PGV), Peak Ground Acceleration (PGA), and Arias Intensity, revealing significant amplification in the central areas of the basin when using 3D models. In contrast, edge zones tend to show neutral or slightly de-amplified responses. These findings underscore the importance of incorporating 3D effects into seismic hazard assessments to improve the accuracy of microzonation strategies.
Future work aims to refine seismic hazard maps by leveraging machine learning techniques to automate the classification of zones based on response spectra and frequency-dependent amplification.
How to cite: Sabback, G., De Martin, F., and Cornou, C.: A Comprehensive Analysis of Seismic Site Effects in the Grenoble Basin (French Alps), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9885, https://doi.org/10.5194/egusphere-egu25-9885, 2025.
It is widely known that the local geology can strongly affect the ground motion by modifying the amplification, duration, and spatial variability of the earthquake shaking. In certain cases, when the ground motion is strong enough, the material may develop large deformations, altering the physical properties of the medium, reducing the shear modulus, increasing the damping, producing liquefaction and permanent displacements among other things. These phenomena belong to the domain of nonlinear soil behavior.
In this study, we use earthquake records collected between 2000 and 2022 from KiK-net stations in Iwate Prefecture (Japan). We investigate three signal processing techniques—deconvolution, phase correlation, and phase autocorrelation—on the earthquake data, focusing on their ability to determine empirical Green’s functions. Our findings show that all three methods give consistent results. Additionally, we group empirical Green’s functions by Peak Ground Acceleration (PGA) into seven bins from 1 to 400 cm/s² and compute an average for each bin. We then apply the stretching technique to determine the velocity change, using the 1-5 cm/s² PGA bin as a reference. This low PGA level is supposed to have linear behavior. We observe that velocity changes increase with increasing PGA. The percentage of velocity changes differs among stations, showing site-specific variations that are not directly correlated with the conventional soil classification based on VS30.
We also investigate temporal variations of velocity changes at each station. We observe a drop in velocity after strong earthquakes, followed by a long-term recovery. This study proposes a new approach to investigate spatial and temporal, linear and nonlinear soil response.
How to cite: Schibuola, A., Lai, S.-T., Stutzmann, É., and Bonilla, F.: Two decades of nonlinear soil response through velocity change analysis in Iwate Prefecture, Japan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12971, https://doi.org/10.5194/egusphere-egu25-12971, 2025.
Over the last 500 years, Tenerife and La Palma (Canary Islands) have suffered several destructive earthquakes, mostly linked to volcanic activity but also generated by regional tectonics. These seismic events can be very shallow and reach moderate magnitudes, as observed in recent volcanic eruptions in the archipelago. The islands' geological complexity can lead to local seismic amplification due to site effects. Therefore, detailed in situ studies of local seismic responses are necessary to assess the seismic hazard correctly.
For these reasons, INVOLCAN has conducted various seismic microzonation surveys in different areas of both islands since 2019. These studies involved principally measuring microtremors in urban areas. The HV method was applied to the large amount of data recorded to determine the predominant frequencies of the ground. The results were compared with existing geological information and geotechnical borehole data.
The first study was conducted in San Cristóbal de La Laguna (Tenerife), whose old town has been declared a universal heritage site by UNESCO. The city is located in a valley filled with lacustrine deposits and lava flow layers, so its local geology makes it susceptible to local seismic amplification effects. In La Laguna, we performed 453 microtremor measurements using broadband stations.
The second study was conducted in La Orotava Valley (Tenerife), where 236 microtremor measurements were taken. This valley originated 500.000 years ago due to a giant gravitational landslide, and nowadays, it is an area hosting significant population centres and key tourist infrastructure.
Finally, the third study was performed in the Aridane Valley (La Palma), where 200 microtremor measurements were obtained. This valley also results from a gravitational landslide of the Cumbre Nueva volcanic edifice. This area was recently affected by the Tajogaite eruption in 2021.
Our main findings are: (1) in the first study, La Laguna Valley is characterised mainly by low frequencies, possibly related to thick lacustrine deposits, but also by secondary high-frequency peaks revealing the existence of thin layers at the surface; and (2) in the other two study areas the frequencies vary between medium-low values that are likely associated with the gravitational landslide deposits.
How to cite: Martínez van Dorth, D., D'Auria, L., Cabrera-Pérez, I., Feriche, M., Palau Erena, A., García-Hernández, R., Ortega Ramos, V., Padilla Hernández, G. D., Przeor, M., and Pérez, N. M.: Seismic microzoning studies in urban areas of Tenerife and La Palma islands, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13732, https://doi.org/10.5194/egusphere-egu25-13732, 2025.
China site database (CNSDB) contains site metadata for 1450 strong motion stations with recordings in the China Flatfile project. The stations are from China National Strong Motion Observation Network System (NSMONS), in 27 provinces of mainland China. The principal site parameters in CNSDB are time-averaged shear wave velocity in the upper 30m (VS30) and site classification results according to China seismic design code. VS30 values are derived or extrapolated when reliable velocity profiles or field survey results are available. The extrapolation relationship is developed according to statistical properties of 6179 engineering boreholes, which is separated into four subregions in China mainland. Besides measurement-based site parameters, CNSDB consists of site parameters derived from the earthquake horizontal-to-vertical spectral ratio (HVSR) curve, including predominant period and amplitude. Our previously proposed machine learning-based HVSR site classification schemes are also utilized to estimate VS30 and China site classifications. For stations without velocity profiles and enough ground motion recordings for HVSR computation, we utilize geology age/genesis, ground surface slope, and terrain category as site description proxies to estimate VS30. We analyze the performance of these proxies in relation to the measured VS30 values and provide the recommended VS30 value and its dispersion. We present protocols for VS30 estimation and China site classification from proxies that emphasize methods minimizing bias and dispersion relative to data. Except for the recommended site parameters results, site characterization proxies for each site and corresponding site parameters are also provided in the open-source site table of CNSDB. This can facilitate the search for the optimal site parameter(s) for the prediction of site amplification in different application occasions, like GMM development, scenario ground motion simulation, and seismic hazard/risk assessment.
How to cite: Ren, Y., Ji, K., Zhang, Y., Yao, X., Si, H., Kishida, T., Liu, Y., Song, J., and Wen, R.: Site database for national strong motion stations in mainland China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14823, https://doi.org/10.5194/egusphere-egu25-14823, 2025.
Coral sand, as a geological material for foundation filling, is widely used for reclamation projects in coral reef areas. The coral sand is characterized by a wide grain size distribution. A series of centrifuge shaking table tests were conducted to explore the seismic response of a shallow buried underground structure in saturated coral sand and coral gravelly sand. The emphasis was placed on comparing the similarities and differences in the dynamic behavior of the underground structure at the two sites. The responses of excess pore pressure, acceleration, displacement, and dynamic soil pressure of the structure were analyzed in detail. The results indicated that the underground structure in coral sand had a significant influence on the development of excess pore pressure in the surrounding soil, but this effect was not evident in coral gravelly sand due to well-drained channels. Liquefaction was observed in the soil layer around the structure in coral sand, but it did not occur in coral gravelly sand. In coral sand, the liquefaction of the soil layer at the bottom of the structure caused a significant attenuation in the acceleration of the structure. Compared to coral gravelly sand, the acceleration response of the soil layer near the bottom of the underground structure was higher in coral sand. During the shaking, the displacement pattern of the structure in coral gravelly sand was slight subsidence-slight upliftsignificant subsidence, while it exhibited a significant uplift in coral sand. The maximum dynamic soil pressure distribution on the structural sidewalls presented a trapezoidal distribution, and the dynamic soil pressure had a strong connection with the development of excess pore pressure in the surrounding soil.
How to cite: Zhang, Z., Chen, S., Wang, Y., and Li, X.: Comparative study on seismic response of a shallow buried underground structure in coral sand and coral gravelly sand by centrifuge modeling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2631, https://doi.org/10.5194/egusphere-egu25-2631, 2025.
An earthquake with a magnitude of M4.8 struck Sumedang, West Java, on December 31, 2023, at a shallow depth of 5 km. This study analyzes strong ground motion data from five nearby accelerograph stations (CSJM, TSJM, TOJI, ACBM, BALE) to evaluate the patterns of Fourier amplitude spectra, spectral response acceleration (PSA), and their implications for building response periods. The results reveal a significant relationship between the station's distance from the epicenter, local geological characteristics, and the earthquake's energy distribution. The CSJM station, located 14.4 km from the epicenter, recorded a dominant frequency of 4.8 Hz with a maximum PSA of 0.17 g in the 0.2–0.3 second spectral period range, reflecting the high-frequency dominance due to its location on dense volcanic deposits and lava formations. The TSJM station, situated 19.5 km away near the Cileunyi-Tanjungsari fault, exhibited the highest PSA amplitude (0.4 g) at a spectral period of 0.3 seconds. This is attributed to the influence of soft soil deposits and active fault proximity, which amplify high-frequency vibrations, presenting challenges for buildings with natural periods within this range. In contrast, the TOJI station (23.6 km) recorded a PSA of 0.1 g at a spectral period of 0.2 seconds with a dominant frequency of 3 Hz, while the ACBM station (34.7 km) showed a PSA of 0.1 g at 0.3 seconds and a dominant frequency of 1.84 Hz, reflecting attenuation of high-frequency seismic energy. The BALE station (35.7 km) exhibited the lowest PSA of 0.05 g at a spectral period of 0.2 seconds, with a dominant frequency of 4 Hz, influenced by its more stable and compact geological formations. These findings indicate that local surface geological effects contribute to the differences in the spectral response amplitude level as the representative of the level of earthquake ground motion itself. These also underscore the importance of understanding building response periods and their interaction with local seismic conditions. Regions near the epicenter, such as CSJM and TSJM, require structural designs that account for high vibrational intensity and shorter periods, while areas farther away, like ACBM and BALE, should consider energy distribution over longer periods for high-rise buildings. This study provides essential insights into seismic risk mitigation and informs earthquake-resistant design practices in compliance with the Indonesian National Standard (SNI 1726:2019).
How to cite: Pramono, S., Rahman, A. S., Prayoedhie, S., Permana, D., Rahmatullah, F. S., Riama, N. F., Octantyo, A. Y., Sativa, O., Habibah, N. F., Sukanta, I. N., Sugianto, D., Pradita, J. S., Kaluku, A., Persada, Y. D., and Silvia, U. N.: Spectral Response Characteristics and Building Response Periods: Insights from the 2023 M4.8 Sumedang Earthquake Ground Motion Analysis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18948, https://doi.org/10.5194/egusphere-egu25-18948, 2025.
This study divides the Yunnan block in China into three regions based on the spatial distribution of historical earthquakes and active faults: Region A (Baoshan-Puer block), Region B (Western Central Yunnan block), and Region C (Eastern Central Yunnan block). These areas, situated `within the Sichuan-Yunnan rhombic block (SYRB) and its adjacent territories, are key seismic hotspots due to the interactions between the Eurasian and Indian plates. Given the difficulty in identifying traditional reference sites, we developed Vs30 velocity profile models for Yunnan Province using regional borehole data. Additionally, we established regional empirical reference site amplification models using the quarter-wavelength method. Using the generalized inversion technique (GIT), we performed joint inversions on 24, 40, and 40 earthquakes in Regions A, B, and C, respectively. Obtaining source parameters for 104 earthquakes, regional quality factors (Q) for the three regions, and local site amplification effects for 124 stations. The stress drop ranged from 0.20 to 6.94 MPa. The average stress drop in Region A (1.61 MPa) is greater than in Region B (1.10 MPa), and Region C (0.77 MPa). Low stress drop areas exhibited a strong spatial correlation with regions of high heat flow, suggesting that high heat flow areas may lead to lower stress drops. These results are consistent with previous studies. The quality factor Q models for Regions A, B, and C are 194.48f0.418, 156.80f0.537 and 382.66f0.322, respectively. The Q value in Region C, near the Sichuan Basin, is significantly higher than in Region B, highlighting notable lateral heterogeneity. The resonant frequencies (fres) of GMX-A, GMX-B, GMX-C, and GMX-D across 124 stations are 7.75, 6.20, 4.69, and 2.15Hz, with corresponding amplification factors of 3.02, 2.57, 6.62, and 6.50. The average amplification factors for GMX-A and GMX-B were similar, as were those for GMX-C and GMX-D. As the site conditions became softer, the peak amplitude plateau shifted to lower frequencies, consistent with the general observation that stiffer sites exhibit higher resonant frequencies. Finally, the parameters obtained from the GIT were used for stochastic finite-fault simulation of the 5% damped PSA, FAS, and acceleration time series of the 2009 Ms 6.3 Yaoan mainshock and two aftershock sequences. The simulation results were consistent with the observed results, validating the reasonableness of the inversion parameters for the Yunnan block.
How to cite: Wang, Z., Chen, S., Fu, L., and Li, X.: Empirical reference site and generalized inversion technique for seismic inversion in Yunnan, China: validation through stochastic simulation of the 2009 Ms 6.3 Yaoan earthquake, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9735, https://doi.org/10.5194/egusphere-egu25-9735, 2025.
Earthquakes had caused devastating damage around the world especially in the countries with the existence of active seismic sources. However, there are many cases where felt tremors and the corresponding destruction can be occurred in the area without the presence of seismically active sources, as per case in the famous case study of Michoacán’s 1985 earthquake. This proved that a far-field earthquake can be as destructive as a near-field earthquake. Throughout the years, Peninsular Malaysia is classified as a low to zero seismicity region, with the local seismic hazard is measured based on the far field and regional earthquake sources. Nevertheless, it should be note that more than 30 local earthquakes had been recorded by the Malaysia Meteorological Department (MMD) for the past decade particularly within the west coast of Peninsular Malaysia. To address the lack of seismic hazard map of the Peninsular Malaysia region, this research work developed an earthquakes’ catalogue using the existing recorded data collected from 1900 till 2016. In addition, average shear-wave velocity (VS30) data was utilized in generating the uniform hazard spectra for nine major cities in Peninsular Malaysia. The comparison between locally derived ground motion prediction (GMP) equation with regional equation has led to a comprehensive probabilistic approach in the new seismic hazard analysis of the region. The hazard map of the selected cities illustrates the probability of exceedance (PE) of 10% and 2% within 50 years are in the range of 10 gal to 50 gal and 20 gal to 80 gal for Return Period of 475 and 2,475 years respectively. Both PE yields similar Peak Ground Acceleration (PGA) distribution patterns where the values decrease northeastward with the sites closer to the local sources was measured having the greater PGA value.
How to cite: Abdul Latiff, A. H.: Revisiting Seismic Hazard of Peninsular Malaysia: Comprehensive PSH Analysis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1377, https://doi.org/10.5194/egusphere-egu25-1377, 2025.
Dersim is located on the eastern part of Turkey and facing major earthquakes. The city is surrounded by four mountains ranges and delimited by different fault segments of the North and East Anatolian Faults. The Yedisu Segment is defined on the North Anatolian Fault Zone (NAFZ) which produced an earthquake of Mw: 7.2 in 1784, while the Bingol Fault which is aligned on the Eastern Anatolian Fault Zone (EAFZ) generated an earthquake of Mw 7.1 in 1866. The Nazımiye Fault parallel to the NAFZ in the south and the Malatya-Ovacık Fault extending along a NE-SW direction on the South of the NAFZ are also active faults which are expected to produce earthquakes greater than 7.5 in the near future. Besides the size of damage due to earthquake hazard in the residential area, it is thought that the city will also be exposed to secondary hazard such as landslide, rockfall, avalanche triggered by an possible earthquake.
Besides the importance of the fault activation, stress change and the earthquake repeat time in the study area, it is aimed in this study to simulate some hazard models and evaluate their dimension. For this purpose, we conducted a field campaign during 2022 and acquired microtremor and ambient noise data at 250 points in an area of 250x250 m grid size. The results were discussed in response to fundamental frequency, amplification and vulnerability maps. Our primary results show that the city is in a high risk location facing serious potentially damage due to a possible earthquake.
Another purpose of this study is to draw attention on how “solidarity” is importance in disaster resilience. The present study is conducted with the collaboration of the local government and limited possibilities. Unfortunately, we have no emergecy funding or financial support for this earthquake hazard study. Therefore, we will invite you to a broader solidarity to manage on this important task.
How to cite: Karabulut, S. and Cengiz, M.: The Lack of Disaster Resilience in a Lonely City Dersim (Tunceli), Eastern Turkey, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5087, https://doi.org/10.5194/egusphere-egu25-5087, 2025.
Probabilistic Seismic Hazard Assessment (PSHA) is a widely used tools to evaluate the threat of seismic events in earthquake-prone regions and is particularly useful for engineering decision-making and setting construction design standards. However, outside of these communities the results of PSHA analysis are non-intuitive, particularly for disaster risk managers. In these cases, specific hazard scenarios are often used to demonstrate the potential scale of the hazard challenge. For scenario-based seismic hazard calculations the aleatory uncertainties are traditionally accounted for by calculating multiple realisations of the ground shaking intensity measure for a given ground motion prediction equation (GMPE). Epistemic uncertainties are usually estimated in earthquake scenarios by considering a weighted statistic - usually the mean or median - of two to four GMPEs. In this study we show that this approach usually overestimates the ground shaking for any particular region.
We propose an updated approach where we calculate ground motions using all available GMPEs instead of a subset of equations. Our GMPE set for the test area in West Java, Indonesia, includes 26 equations relevant for Active Shallow Crust environments. Using the Global Earthquake Model OpenQuake-engine we calculate 1000 realisations of each GMPE, merge the histograms of all realisations for all GMPEs into a single ground motion prediction set for each site location. We show that this histogram approximates a lognormal distribution. We show that the mean or median both overestimate the likely ground motions by over 71% and 37% respectively compared to the maximum of the kernel density estimator, which better represents the peak of the distribution. We apply this new method to investigate the shaking distribution from a number of earthquake rupture scenarios on the Lembang Fault and the Cimandiri Fault and test the impacts of a potential joint rupture across both faults, a situation often deemed to be the worst-case scenario for the region.
How to cite: Hussain, E., Gunawan, E., Hanifa, N. R., Putra, D. D., and Alam, K. A.: Rethinking epistemic and aleatory uncertainties for seismic hazard scenarios: A case study of the Lembang and Cimandiri faults in Indonesia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6838, https://doi.org/10.5194/egusphere-egu25-6838, 2025.
This seismic hazard assessment aims to determine design parameters and develop design response spectrum for the dam body by evaluating nearby active faults, historical earthquake activity, and local site conditions in Pakistan. This project holds significant importance for optimizing water resource utilization and enhancing the country's infrastructure development.
The dam is situated at the Tethysides-Indian Craton boundary, a major paleotectonic division of Eurasia. This area lies within the Alpine-Himalayan orogenic belt, an extensive seismic and mountainous region spanning over 15000 km. Notably, the Kirthar Fold and Thrust Belt (KFTB) extends over 200 km along the western boundary of the Indian plate. The tectonic setting of the KFTB is primarily influenced by the Indian-Eurasian plate collision within the Central Kirthar Fold Belt. Detailed descriptions of the KFTB and adjacent active faults are available in the Active Faults of Eurasia Database which prepared by Geological Institute of the Russian Academy of Sciences.
The closest active fault is approximately 2 km from the dam site. Within a 200 km radius of the dam, 19 earthquakes with magnitudes of 6.00 or larger have occurred over the past 115 years. Significant seismic events include the Mw7.16 earthquake on October 20, 1909 (28 km away from dam body), the Mw6.75 event on October 15, 1928 (14 km away from dam), and the Mw6.05 event on May 15, 1935 (13 km away from dam).
A total of 2363 earthquake records with magnitudes of 4.00 or larger were collected from 17 different catalogs. After removing foreshocks and aftershocks using the Gardner and Knopoff (1974) method, 403 records remained. Recurrence parameters were then calculated using the Weichert (1980) approach. The site classification, based on a measured shear wave velocity of 600 m/s from the MASW report, corresponds to Classes "C" and "B" per ASCE 7-16 and Eurocode 8 standards for Vs30.
Ground motion predictions were generated using OpenQuake with GMPEs from Abrahamson et al. (2014), Boore et al. (2014), Campbell & Bozorgnia (2014), and Chiou & Youngs (2014), as recommended by the International Commission on Large Dams (ICOLD). These models contributed 50% to the final results. The remaining 50% was derived from GMPEs advised by the 2014 Earthquake Model of the Middle East (EMME14) Project under the European Earthquake Hazard and Risk Facilities (EFEHR), including models by Akkar et al. (2014), Chiou & Youngs (2008), Akkar & Çağnan (2010), and Zhao et al. (2006).
Both Deterministic Seismic Hazard Analysis (DSHA) and Probabilistic Seismic Hazard Analysis (PSHA) results will be presented using these GMPEs. Median and +1 standard deviation values are calculated for DSHA, while PSHA results include calculations for seven return periods (72, 144, 475, 975, 2475, 5000, and 10000 years). The final risk classification will follow the guidelines outlined in ICOLD documentation.
How to cite: Deneri, A. H. and Selvi, M.: Seismic Hazard Assessment for a Dam Project at the Eurasian Indian Plate Boundary, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19288, https://doi.org/10.5194/egusphere-egu25-19288, 2025.
This study presents a machine learning (ML) model aimed at capturing local site effects on seismic ground motion. Synthetic seismic spectrums are first generated using moment tensor solutions and a Green's Function Database from Pyrocko. Residuals between observed and synthetic data are computed in octave frequency bands, reflecting deviations introduced by site-specific conditions. These discrepancies are then modeled using a feedforward neural network trained on both normalized synthetic spectrums and site-specific parameters (e.g., bedrock depth, average shear-wave velocity, fundamental frequency). We demonstrate the effectiveness of this approach by applying it to Japan’s complex seismic environment, using strong-motion records from the K-NET and KiK-net networks. Once trained, the model accurately predicts and corrects these discrepancies, reconstructing spectrums that closely match real observations. This approach not only significantly enhances the interpretation of seismic data but also boosts earthquake hazard prediction in regions with complex site-effects. Overall, this framework provides a powerful tool for reducing the gap between simulated and actual ground motion, ultimately improving the reliability of seismic risk assessments.
How to cite: Cardellini, D., Hammer, C., and Ohrnberger, M.: A Machine Learning Framework for Enhanced Site-Specific Ground Motion Modeling , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13695, https://doi.org/10.5194/egusphere-egu25-13695, 2025.
In the Taiwan seismic design code for buildings, damping modification factors (i.e., B values) are provided as a denominator to calculate the elastic design basis response spectra with damping ratios other than 5%. At short periods and at one-second period, the B values are referred to as Bs and B1, respectively. Those values are originally proposed to derive the corresponding design basis response spectra rather than maximum considered ones. According to some observed earthquake records and past relevant studies, it is found that damping modification factors are greatly related to natural periods, at long periods in particular. In addition, some recent studies indicate that damping modification factors, to some extent, are relevant to some ground motion characteristics that are used in ground motion prediction equations, e.g., moment magnitude (MW), rupture distance (Rrup), averaged shear wave velocity in the upper 30 m of sites (Vs30), etc. Therefore, by means of abundant ground motion database recorded in Taiwan, this study aims to develop empirical and localized models for estimating suitable damping modification factors in terms of spectral displacement, velocity, and acceleration. The models are proposed in the form of not only damping ratios and natural periods but also MW, Rrup, duration, and Vs30. Through comparing the damping modification factors obtained from the proposed models with those specified in the current design code, the applicability of the code-specified values is further examined. Moreover, the results obtained from the models determined using the entire ground motion database can satisfactorily reproduce the response spectra of several near-fault pulse-like ground motions with damping ratios different from 5%. It is further implied that the proposed model is robust sufficiently and valid for both far-field and near-fault pulse-like ground motions. The results show that the damping modification factors provided in the current design code are acceptable practically when the damping ratio falls within 2% to 25%, while those may be too conservative when the damping ratio is smaller than 2%.
How to cite: Chang, Y. W., Liu, C. C., and Wang, S. J.: Empirical Ground Motion Model for Damping Modification Factor for Horizontal Response Spectra in Taiwan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15723, https://doi.org/10.5194/egusphere-egu25-15723, 2025.
Ground motion simulation is crucial for seismic risk assessment in cities with limited recorded strong ground motion data. Lebanon is located along the Dead Sea Transform fault system, which previously generated large earthquakes, but has recently experienced only low to moderate instrumental seismicity. Beirut, the capital of Lebanon, was destroyed in 551 AD due to a large magnitude earthquake (MS7.3) offshore Lebanon that was attributed to the Mount Lebanon Thrust fault (MLT). In addition, Beirut is densely populated nowadays, and seismic design requirements were only recently introduced in Lebanon. Thus, seismic risk assessment studies for Beirut should consider large-magnitude earthquake scenarios on the MLT, e.g., similar to the 551 AD historical earthquake. The lack of strong motion records from the MLT source underscores the need for ground motion simulation. In this work, we first identify the plausible earthquake scenarios on the MLT by fitting radiocarbon-dating and uplift data at the Lebanese coast to simulated static deformations from scenarios on the MLT. Next, we develop a improved hybrid ground motion simulation method, which combines deterministic simulations at low-frequency (LF) (<0.5 Hz) and a stochastic approach at high-frequency (HF). The LF part is based on pseudo-dynamic rupture models and a recently developed one-dimensional velocity model of Lebanon. On the other hand, the HF part consists of an improved version of a near-fault site-based stochastic model that accounts for specific features of near-fault ground motions, such as directivity velocity pulses, conditioned on the LF ground motion properties. Using this model, we simulate ground motions at a grid of virtual stations in Beirut. These simulations will be used in future works for a city-scale comprehensive structural damage estimation in Beirut for the selected scenarios.
How to cite: Al Jamal, H., Causse, M., Cornou, C., and Dabaghi, M.: Ground motion simulation in Beirut from a large earthquake on the Mount Lebanon Thrust fault, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15853, https://doi.org/10.5194/egusphere-egu25-15853, 2025.
Recently, several studies have shown that the hybrid ground motion prediction equation (GMPE), which predicting the ground motion intensities (GMIs) of on-site S-wave by involving the observed GMIs of on-site P-wave, can improve the prediction accuracy and reduce the aleatory uncertainty for the on-site ground motion in respect to general ergodic GMPE due to high correlation between GMIs of on-site S-wave and on-site P-wave. This hybrid GMPE can be applied for the on-site and the hybrid early warning systems to improve the performance of the alert message. However, the possible spatial correlations between the residuals of the hybrid GMPE, which can be used to develop non-ergodic correction terms to improve the prediction accuracy for the sites nearby the strong motion instruments, haven’t not been evaluated. In this study, we evaluate the pre-mentioned spatial correlations and use it to develop the Taiwan non-ergodic hybrid GMPE based on the developed ergodic hybrid GMPE for two different kinds of GMIs (spectral acceleration and instantaneous power at different periods). The performance of the proposed Taiwan non-ergodic hybrid GMPE with respect to the ergodic GMPE and the non-ergodic GMPE for the application of the earthquake early warning and the post-earthquake ShakeMap is also evaluated in this study. The output of this study would be beneficial for evaluating and determining the microzonations of earthquake early warning and seismic design code.
How to cite: Chao, S.-H., Huang, J.-Y., and Sung, C.-H.: Taiwan Non-Ergodic Hybrid GMPE for Improving the Accuracy of Earthquake Early Warning and Post-Earthquake ShakeMap, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20542, https://doi.org/10.5194/egusphere-egu25-20542, 2025.
Rapidly determining seismic source characteristics, particularly the moment tensor and finite-fault inversion, is critical for providing timely and detailed information for rapid responses to large earthquakes. We proposed an automatic method to improve the efficiency of these inversions, which was limited previously by using far-field data in moment tensor inversions and manual operation in finite-fault inversions. Using near-field data, we simultaneously determined the moment tensor solution and the horizontal moment distribution. It can recover the source mechanism and identify moment-concentrated regions based solely on preliminary location and magnitude results. In addition, by solving the horizontal moment distribution, this approach can handle ruptures on complex fault systems, including curved, branched, parallel, and conjugated faults. The effectiveness of this method was validated through numerical tests and applications to the 2008 Wenchuan and 2016 Kaikōura earthquakes. By utilizing real-time near-field data, this method can identify meizoseismal areas within minutes after an earthquake, providing valuable insights for intensity distribution and disaster assessment.
How to cite: Xu, C. and Zhang, Y.: Simultaneous Determination of Focal Mechanism and Moment Distribution for Rapid Responses to Large Earthquakes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10663, https://doi.org/10.5194/egusphere-egu25-10663, 2025.
Posters on site: Fri, 2 May, 10:45–12:30 | Hall X1
In recent years, new seismological, geophysical and geological results have been obtained (Porkoláb et al. 2024, Koroknai et al. 2024, Czecze et al. 2024) and new methods have been developed, necessitating an update to the national seismic hazard map of Hungary. One of the most important steps in this update is to analyze how earthquake-induced ground motion attenuates with source-site distance and magnitude, which can be determined through ground motion prediction equations (GMPEs). Zsíros (1996) found that in the Pannonian Basin, macroseismic intensities attenuated with distance more rapidly than in other regions with comparable low to moderate seismicity — a result that also was corroborated during local magnitude calibration for the area. In the absence of strong motion stations in Hungary, we have to use equations based on records from areas of high seismicity, after proper validation. The selection of GMPEs to perform seismic hazard assessments is challenging for the specific characteristics of the Pannonian Basin, such as shallow crustal earthquakes, thin and warm crust, elevated heat flux, and the lack of a sufficient number of medium and large earthquakes. Due to medium seismicity and the lack of strong motion stations, we can only use weak motion records for the research. Our research focuses on gathering and processing of digital records of medium-magnitude earthquakes in the Pannonian Basin since 1995 and recorded by stations in Hungary, surrounding countries, as well as by temporary stations of international projects. This includes calculating various motion parameters and formulating a distance- and magnitude-dependent attenuation equation that fits this dataset. We select GMPEs developed for high seismicity, active shallow crustal zones. Statistical approaches, including the classical residual, likelihood, and log-likelihood are used to evaluate the performance of the GMPEs. This study's outcomes recommend GMPEs optimized for probabilistic seismic hazard analysis in Hungary, considering the basin's distinct seismic attributes.
References:
Czecze B., Győri E., Timkó M., Kiszel yM., Süle B., & Wéber Z. (2024). A Kárpát-Pannon régió szeizmicitása: aktualizált és átdolgozott földrengés-adatbázis. Földtani Közlöny, 153(4), 279. https://doi.org/10.23928/foldt.kozl.2023.153.4.279
Koroknai B., Békési E., Bondár I., Czecze B., Győri E., Kovács G., Porkoláb K., Tóth T., Wesztergom V., Wéber Z., & Wórum G. (2024). Magyarország szeizmotektonikai térképe. Földtani Közlöny, 153(4), mapD. https://doi.org/10.23928/foldt.kozl.2023.153.4.mapD
Porkoláb, K., Békési, E., Győri, E., Broerse, T., Czecze, B., Kenyeres, A., ... & Wéber, Z. (2024). Present-day stress field, strain rate field and seismicity of the Pannonian region: overview and integrated analysis. Geological Society, London, Special Publications, 554(1), SP554-2023.
Zsíros, T. (1996) Macroseismic focal depth and intensity attenuation in the Carpathian region. Acta Geod. Geoph. Hung. 31, 115-125.
How to cite: Csatlós, M., Győri, E., and Süle, B.: Attenuation of seismic waves in the Pannonian Basin , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-32, https://doi.org/10.5194/egusphere-egu25-32, 2025.
The horizontal to vertical spectral ratio (H/V) method is a widely used technique for assessing subsurface characteristics. It analyzes the ratio between horizontal and vertical seismic components of ambient vibrations (microtremors), providing valuable insights into the dynamic properties of the soil. This method is crucial in understanding soil behavior, including its fundamental frequency, site response, and dynamic soil conditions. Specifically, the H/V spectral ratio is useful in evaluating dynamic soil properties such as liquefaction, settlement, and variations in soil stiffness. These phenomena are particularly prominent in regions with high water tables, where soil may undergo liquefaction during seismic events, causing significant structural damage. Analyzing shifts in the H/V ratio can provide a better understanding of these soil behaviors and help predict the potential impacts of seismic events. The H/V technique is also a valuable tool in microzonation studies, which assess seismic hazards based on soil conditions, playing a crucial role in urban planning and construction.
On February 6, 2023, the Kahramanmaras region in Türkiye experienced a devastating earthquake with a magnitude of 7.7. This earthquake, one of the most destructive in Türkiye's history, caused significant loss of life and extensive damage to buildings, especially in Kahramanmaras and surrounding areas. The event was followed by a strong aftershock on the same day, further increasing seismic activity in the region. The Kahramanmaras earthquake highlighted the importance of understanding how strong seismic forces impact soil properties, making this analysis highly relevant for seismic risk assessments. Shifts in soil behavior due to such earthquakes must be closely studied to improve future risk management and construction practices.
This study analyses continuous seismic data collected from monitoring stations in Kahramanmaras and surrounding areas. The data will be used to observe changes in the H/V spectral ratios before and after the earthquake. These measurements will offer valuable insights into shifts in soil fundamental frequencies and structural changes following the earthquake. The hypothesis of this study is that changes in soil stiffness and structure will be reflected in these spectral shifts, which are essential for seismic hazard assessment, especially in urban areas. Understanding these changes is crucial not only for earthquake preparedness but also for improving construction practices in earthquake-prone regions. The findings of this study will help enhance safety measures and disaster response strategies by providing insights into the dynamic behavior of soil during seismic events. Additionally, the data will contribute to more informed decisions in urban development, helping mitigate potential damage caused by future earthquakes.
In conclusion, analyzing H/V spectral ratios following the Kahramanmaras earthquake is an essential step in assessing the impact of seismic forces on soil properties. The results from this study will significantly contribute to earthquake risk management and the development of safe urban planning strategies in seismic zones.
How to cite: Aba, M. C., Ertuncay, D., and Duran, P.: Post-Earthquake Site Characterization of Southeastern Türkiye: An Evaluation Using H/V Analysis Method, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-659, https://doi.org/10.5194/egusphere-egu25-659, 2025.
The Shillong Plateau (SP) is globally renowned for its high seismic activity. The seismicity is mainly caused by the subduction of the Indian plate beneath the Eurasian and Burmese plates in the north and west respectively, in addition to the popup of SP. In the present study, we analyse the seismicity of the SP and adjoining region bounded by latitude from 22.8°N to 28.5°N and longitude 87.5°E to 95.5°E using earthquake data of 825-2024 acquired from national, international, and literature sources. Ten time windows namely 825-2024, 2019-2024, 2008-2018, 825-1800, 1997-2007, 1986-1996, 1975-1985, 1964-1974, 1901-1963, and 1801-1900 have been considered to estimate and compare the spatio-temporal variation of seismicity parameters. We estimated the spatio-temporal variation of the magnitude of completeness (MC), a-value, b-value, and fractal dimension (DC) of the considered region. MC, a-value, and b-value for the above time windows range from 4.70 to 5.70, 4.36 to 9.85, 0.52 to 1.59, however, spatial mapping of MC, a-value, and b-value at each node of the grid of 0.05°×0.05° range from 4.10 to 5.82, 4.46 to 18.94, 0.58 to 3.66 respectively. Spatial mapping of DC at each node of the grid of 1°×1° and 0.5°×0.5° range from 0.258 to 2.240 and 0.462 to 2.164 respectively, however, temporal variation of DC ranges from 0.344 to 2.842. The relationship between b-values for 825-2024 and DC-values shows a positive correlation, while a negative correlation exists between -values and DC-values. The spatio-temporal distributions of these parameters reveal insights into the regional variation of stress levels and geological complexity, which can be used as input for seismic hazard estimation.
How to cite: Shahabudddin, M. and Mohanty, W. K.: Spatio-temporal mapping of seismicity parameters in Shillong Plateau and adjoining regions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1462, https://doi.org/10.5194/egusphere-egu25-1462, 2025.
In deterministic seismic hazard analysis, the worst-case scenario or maximum credible earthquake is used to estimate the seismic ground-motion intensities, which is crucial for the seismic design of key facilities. The stochastic finite-fault method has been proven to enable reliable simulations of the near-field ground-motion parameters of large earthquakes, which can effectively synthesize Fourier amplitude spectra, response spectra, and the time history of acceleration.
The Longpan hydropower station is located in northwest Yunnan Province in the middle reaches of the Jinsha River, on the southwestern margin of the Tibetan Plateau (Figure 1a). As shown in Figure 1b, the seismic structure in the study area is very complex. The source models of the Daju–Lijiang, Xiaozhongdian–Daju, and Longpan–Qiaohou faults were established based on geological and geophysical data. To perform physics-based ground-motion simulation via the stochastic finite-fault simulation, the regional specific ground-motion characteristics can be approximately described by several critical parameters. By applying the multi-scheme stochastic finite-fault simulation method (multi-SFFSM), parameter uncertainty in ground-motion simulations and the impact of the three faults were analyzed on the PGA value and pseudo-spectral acceleration response spectra (PSA) at the target dam to determine the maximum credible ground-motion parameters. The flowchart of our study is shown in Figure 2.
Figure 1. (a) Tectonic locations of the study area. (b) Seismotectonic map of the hydropower station. F1: Changsongping–Wenming fault; F2: Xiaozhongdian–Daju fault; F3: Daju–Lijiang fault; F4: Chongjianghe fault; F5: east of Jinsha River fault; F6: Jinsha River fault; F7: Longpan–Qiaohou fault; F8: Xiaojinhe–Lijiang fault; F9: Heqing–Eryuan fault; F10: Weixi–Qiaohou fault; F11: Honghe fault.
Figure 2. Flowchart of the multi-scheme stochastic finite-fault simulation method.
The results showed that the Longpan–Qiaohou fault can generate the largest ground-motion parameters compared with the other two faults. Moreover, this result was supported by the statistical analysis of the results of six thousand simulations of these three faults. Thus, it can be concluded that the maximum credible ground-motion parameters are represented by the 84th-percentile pseudo-spectral acceleration response spectrum of the Longpan–Qiaohou fault. This finding will benefit the seismic safety design of the target dam. More importantly, this multi-scheme method can be applied to other key facilities to obtain reasonable ground-motion parameters.
How to cite: Li, J.: Assessing Maximum Credible Ground-Motion Parameters of Large Earthquakes at Near-Field Site, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2121, https://doi.org/10.5194/egusphere-egu25-2121, 2025.
The Guangdong-Hong Kong-Macao Greater Bay Area (GBA), a densely populated region, plays a vital role in the economic development of East Asia. The accurate thickness of near-surface loose sediment layers plays an important role in the construction and development of the GBA. However, traditional drilling and active source methods that can obtain this property are often not suitable for large-scale applications in densely populated areas due to their high cost and destructive nature. The ambient noise tomography method based on dense array is an economical and environmentally friendly approach with the advantages of a broad detection range, high resolution and high detection accuracy. Using this approach, a dense array comprising 6214 stations spanning over 60*60 km2 was deployed, and the noise horizontal-to-vertical spectral ratio method was employed to determine fundamental frequency (f0) and peak amplitude. The Quaternary sediment thickness was further estimated based on their empirical relationships with f0. The comparison with the drilling results shows that our estimation is accurate. More importantly, several buried paleochannels were identified, manifesting deep valleys on the vertical section and curved stripes on the horizontal section. Combining regional drilling data and sites of geological disasters in the past, we conclude that the paleochannels pose the highest risk of seismic and geologic hazards. This study provides scientific basis for urban construction and disaster prevention.
How to cite: Ye, X., Xiong, C., Deng, Y., Wang, L., Zhang, Y., Lv, Z., Wang, X., Gong, X., and He, X.: Quaternary sediment thicknesses, paleochannels and hazard assessment revealed by a dense array in the Guangdong-Hong Kong-Macao Greater Bay Area, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2219, https://doi.org/10.5194/egusphere-egu25-2219, 2025.
The forearc mantle wedge has long been considered unsuitable for earthquake nucleation due to its physical properties. With advances in seismic instrumentation, some cold subduction zones have revealed seismic clusters within this region (e.g., Greece, Japan, New Zealand, Lesser Antilles - LA). The maximum earthquake magnitude potential in the mantle wedge remains unknown. In the LA, this seismicity is located approximately 50 km east of the French island coasts, at depths of 25 to 60 km. The 1974 earthquake (M = 6.9-7.5) is estimated to have occurred just below the current Moho depth. The limited azimuthal coverage of the seismic network makes the characterization of mantle wedge seismicity as seismic source challenging. By analyzing secondary phases in local earthquake waveforms, we can achieve more robust source region identifications. We extracted 15 earthquake waveforms to be analyzed and used as references for the central LA mantle wedge seismicity. We are currently using this database to analyze 778 earthquakes, which we have identified as potential mantle wedge events based on subduction geometry. As part of the Atlas project for the LA seismic hazard reassessment, we will use our catalog to estimate the a- and b-values, and assess the impact of this seismicity on ground motion.
How to cite: Foix, O., Halpaap, F., Rondenay, S., Bodin, T., Laigle, M., Ambrois, D., and Maufroy, E.: Mapping Mantle Wedge Seismicity for seismic Hazard Assessment: The Lesser Antilles Subduction Zone Case, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4134, https://doi.org/10.5194/egusphere-egu25-4134, 2025.
It is well known that near-field earthquake ground motion can be characterized by strong velocity pulses that may cause extensive damage to buildings and structures, as recently documented for the Mw 7.8 and Mw 7.5 earthquake doublet of the 2023 Turkey seismic sequence.
Usually only directivity pulses are investigated, neglecting other characteristics such as unilateral/bilateral shape, presence of multiple-pulses as well as other features that can support classification of pulse causes. As observed in recent studies on the directivity pulses of the 2023 Turkey seismic sequence (e.g. Yen et al., 2025), this practice leads to a significant variability in the pulse properties of the observed records, highlighting that factors beyond rupture directivity also play a crucial role in shaping pulse characteristics, such as site effects, permanent ground displacements, local heterogeneities in slip amplitude, orientations, and fault kinematics.
In this study, we provide a methodology that combines different approaches (Baker et al., 2007; Shai and Baker, 2011, 2014; Ertruncay and Costa, 2019; Chen et al., 2023; Chang et al., 2023) for pulse detection and classification. The aim is twofold: on one hand, we aim to extend metadata assignment for a better characterization of pulse properties; on the other hand, we provide a ML-ready dataset to support development of advanced ML techniques for pulse classification. Indeed training of ML-based algorithms needs the availability of large labelled high-quality dataset. For this purpose, we exploit two comprehensive worldwide datasets of near-source records: the NESS2.0 (Sgobba et al., 2021), which collects real earthquake records, and the BB-SPEEDset (Paolucci et al., 2021), consisting of ground motion data from 3D Physics-Based Numerical Simulations.
How to cite: Mascandola, C. and Sgobba, S.: Ground motion pulse-like detection and classification: combining different approaches for comprehensive metadata assignment supporting ML techniques for engineering applications , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4379, https://doi.org/10.5194/egusphere-egu25-4379, 2025.
Accurate prediction of broadband ground motion parameters is important for earthquake disaster prevention and mitigation. Due to lack of high wavenumber components of the source rupture process and the velocity models, physics-Based ground motion simulation methods can only produce reliably low-frequency ground motions (<1 Hz). In this study, we developed a deep learning network, LFW2BBP, which maps physics-based simulated low-frequency ground motion waveforms to broadband ground motion parameters. LFW2BBP extracts features of low-frequency ground motion in time domain waveforms, time-frequency domain spectrum and spectrum acceleration, and integrates these features to establish a relationship with high-frequency ground motion parameters. Sensitivity tests are conducted to verify the stability and robustness of the LFW2BBP. Finally, we combined physics-based simulation and LFW2BBP to predict broadband ground motion parameters for the 2016 Mw 7.0 Kumamoto earthquake. The predicted results show good agreement with the observations.
How to cite: Pan, Y., Zhang, W., Zang, N., and Chen, X.: LFW2BBP: Broadband Ground-Motion Parameters Estimation Using Physics-Based Simulated Low-frequency waveforms and Deep Learning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9222, https://doi.org/10.5194/egusphere-egu25-9222, 2025.
Irrespective of the tectonic setting hydrological factors play an important role in influencing earthquake activity of region. This study investigates the influence of hydrological factors on earthquake occurrence in the Delhi-NCR region using satellite-based data from GRACE, GRACE-FO, CHIRPS, and GNSS. Analysis reveals a significant decline in groundwater levels despite relatively stable rainfall, indicating substantial anthropogenic groundwater extraction. The spatial analysis reveals a correlation between earthquakes and regions with higher rainfall and groundwater levels, primarily in the northern part of the Delhi-NCR region, which is closer to the Himalayas. Where less rainfall and low groundwater levels in the region lead to sporadic earthquakes, particularly in the southern part of Delhi NCR, where the Delhi supergroup rocks are exposed. Temporal analysis, however, reveals subtle relationships. In the northern region of Delhi-NCR, which is closer to the Himalayan region, earthquakes tend to follow periods of post-monsoonal elevated groundwater unloading, while in the southern region, with greater rock exposure, seismic activity correlates more strongly with rainfall patterns. These findings highlight the importance of considering hydrological factors, particularly anthropogenic impacts on groundwater resources, in seismic hazard assessments for the Delhi-NCR region.
Keywords: Groundwater, Rainfall, Earthquake, Unloading.
How to cite: Bhattacharjee, S., Prajapati, S. K., Shankar, U., and Mishra, O. P.: Spatiotemporal Patterns of Earthquake Occurrence and Their Relationship to Hydrological Parameters in the Delhi-NCR., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9286, https://doi.org/10.5194/egusphere-egu25-9286, 2025.
Türkiye is located in a highly active seismic region. The North Anatolian Fault Zone (NAFZ) and the East Anatolian Fault Zone (EAFZ) were formed due to the collision of the Arabian Plate with the Eurasian Plate, the resulting movement of the Anatolian block (to the westward). Due to these tectonic movements, highly destructive earthquakes often occur in the NAFZ and EAFZ.
The most destructive earthquake doublets of the last century occurred on February 6, 2023, along the EAFZ. The first earthquake, with a moment magnitude (Mw) of 7.7 (according to AFAD), occurred at 04:17 local time with its epicenter located near Pazarcık in Kahramanmaraş, Türkiye. Its focal depth was calculated to be 8.6 km. A second major earthquake with a magnitude of 7.6 occurred near Kahramanmaraş (specifically in Elbistan) nine hours later. Its epicenter point was determined about 62 km from Kahramanmaraş. Its focal depth was calculated to be 7.0 km. The earthquake doublets on February 6, 2023, in Pazarcık and Elbistan (Kahramanmaraş) caused devastating damage and loss of life across 11 provinces, particularly in Kahramanmaraş and Hatay.
This study aims to conduct a pre-dominant period based seismic hazard assessment for Hatay province following two major earthquake doublets on February 6, 2023, in Türkiye. For this purpose, we utilized earthquake data of various magnitudes recorded by 10 earthquake stations managed by AFAD, located around the center of Hatay. We selected the earthquakes (the S-Wave windows part) and created soil pre-dominant period curves by applying the Horizontal to Vertical spectral ratio method. Site classification for the region was determined based on the predominant period values identified by Zhao et al. (2006) (Z-6), Fukushima et al. (2007) (F-7), and Di Alessandro et al. (2012) (DA -12). The preliminary results, the site classification for station 3123 has been identified as CL-I, as references by DA -12, SC-I by Z-6, and SC-1 by F-7. According to site classification results, the Spectral Acceleration (SA) curves were calculated by using the Ground Motion Prediction Equation (GMPE) developed by DA-12 (based on the dominant period values). These estimated values were then compared with the design spectra outlined in the Turkish Building Earthquake Code (TBEC 2018) and different GMPE proposed by Akkar et al. (2014). Thus, the regional seismic hazard for Hatay province was assessed according to scenario earthquakes.
How to cite: Coban, K. H. and Bayrak, E.: Seismic hazard assessment based on the pre-dominant period after the February 6, 2023, Türkiye earthquake doublets: A case study of Hatay province, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10408, https://doi.org/10.5194/egusphere-egu25-10408, 2025.
Strong ground motion during large earthquakes can cause significant damage to the buildings and infrastructure, as well as disrupt society. Ground Motion Prediction Equations (GMPEs) play a crucial role in seismic hazard analysis for tectonically active regions where the strong ground motion data is available. Over the years, numerous GMPEs have been developed for various parts of the world, and the region-specific GMPEs are particularly important for the accurate seismic hazard analysis. Myanmar, located at the eastern margin of the Indian-Eurasian plate subduction zone, is one of the most tectonically active regions in Southeast Asia. It hosts a complex network of faults, including the Sagaing fault – a 1400 km long dextral fault with an estimated slip rate of 20 mm/year. Historically, there are many large earthquakes in Myanmar that have caused major damage. Despite the long history of earthquakes and the region’s vulnerability to seismic hazards, no GMPE has been developed for Myanmar due to the lack of seismic stations in the past. Leveraging the local seismic network installed in the late 2017, we now have the opportunity to look into the recorded waveforms and address the ground motion analysis for Myanmar. We aim to develop a GMPE for Myanmar region as this would greatly benefit the local communities by providing more accurate seismic hazard assessments, improving the infrastructural design to be earthquake resistant, and enhancing the seismic risk mitigation efforts. Despite the limited dataset of 5 years (2016-2021) and lack of records from large earthquakes such as Mw > 7, we strive to derive a GMPE that effectively represents regional seismic characteristics and fits the recorded data. This initiative marks a critical step toward enhancing seismic safety and resilience in Myanmar.
How to cite: Oo, W. S. S., Chen, G., Lythgoe, K., Maung, P. M., and Wei, S.: Ground Motion Prediction Analysis of Myanmar, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12234, https://doi.org/10.5194/egusphere-egu25-12234, 2025.
Earthquake Early Warning Systems (EEWS) are systems designed to detect earthquakes at the earliest possible moment and issue warnings by assessing whether the detected earthquake is likely to cause significant damage. The branches of the North Anatolian Fault, which were expected to produce a major earthquake but remained unruptured during the August 17, 1999 earthquake, are predominantly located in the Sea of Marmara and have been seismically quiet for an extended period.
The geographic limitations of seismic networks present significant challenges to traditional Earthquake Early Warning Systems (EEWS). For instance, in-land seismic events, such as those originating in the Sea of Marmara, often generate strong ground motions along coastal areas, complicating the determination of source locations. Global studies demonstrate that integrating array methodologies into EEWS—particularly through the deployment of small-aperture arrays in strategic locations—can effectively address these challenges. Such enhancements significantly improve the capabilities of traditional seismic networks, especially in regions with sparse station coverage or areas outside the optimal range of existing networks.
This study focuses on the use of Internet of Things (IoT) devices for delivering Earthquake Early Warning Signals in the Marmara Region, a high-seismic-risk area. IoT technology enables real-time data collection and rapid dissemination of warnings, overcoming some limitations of traditional seismic networks. By improving coverage and communication speed, IoT-based systems offer a more efficient approach to earthquake preparedness. This paper discusses the framework, implementation, and challenges of integrating IoT devices into existing warning systems, highlighting their potential to enhance public safety and reduce earthquake-related risks.
How to cite: Tunc, S.: Public Announcement of Earthquake Early Warning Signal via IoT Devices in the Marmara Region, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15131, https://doi.org/10.5194/egusphere-egu25-15131, 2025.
The Vrancea region, located in the south-eastern Carpathians, Romania, is a unique site of intracontinental intermediate-depth seismicity. Renowned for its frequent large earthquakes exceeding magnitude 6.5, this narrow seismogenic volume significantly impacts Central and Eastern Europe. The seismicity of the Vrancea Zone is concentrated within a vertical NW-SE structure extending from 70 to 180 km depth (Ismail-Zadeh et al., 2012). This depth range is critical for understanding the ground motion effects on the surface. Previous models of the area treated this depth range as a single, undifferentiated source, overlooking the depth-dependent characteristics of earthquake generation and consequent ground motion.
In this study, we conduct an in-depth seismic hazard analysis for Vrancea intermediate-depth earthquakes, emphasizing the role of depth variability in shaping surface ground motion. Using the novel 3D adaptive smoothed seismicity approach by Pandolfi et al. (2023, 2024), we forecast earthquake rates based on precise spatial distributions of seismicity within a 3D grid. This method smooths earthquake locations using a depth-sensitive kernel, with adaptive smoothing distances that account for both high- and low-seismicity areas.
Our analysis utilizes the ROMPLUS catalog (Oncescu et al., 1999), spanning over a millennium (1000–2023) and focusing exclusively on depths between 70 and 180 km to isolate intermediate-depth events. We determined the magnitude of completeness (Mc), computed the b-value, and declustered the catalog using a procedure which considers the earthquake’s location in depth. We also applied a 3D log-likelihood optimization to calibrate the neighboring number (NN) for the adaptive smoothing process. Finally, seismic hazard was assessed using the Vrancea-specific ground motion prediction equation developed by Manea et al. (2021).
This study quantifies the contribution of earthquakes at different depths to ground motion, enhancing our understanding of depth-dependent seismic hazard in the region and providing refined and innovative tools for seismic hazard assessments.
How to cite: Pandolfi, C., Taroni, M., and Akinci, A.: Assessing the Impact on Ground Motion of Intermediate-depth Earthquakes in the Vrancea Zone, Romania, using a 3D Grid-based Approach, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15194, https://doi.org/10.5194/egusphere-egu25-15194, 2025.
Understanding earthquake source properties, such as the seismic moment (M₀), is vital in seismology due to its direct correlation with fault dimensions and slip. The objective of the study which focuses on Northeastern Italy is to define an empirical relation between seismic moment and S-wave peak displacement specific to the region's attenuation characteristics. The seismic moment is being obtained by fitting the omega-squared Brune source model to the low-frequency part of the source spectrum which is achievable by applying a spectral decomposition approach known as the Generalized Inversion Technique (GIT), in which an overdetermined linear system of equations is being solved for the displacement spectrum of seismic data. Finally, the region's attenuation parameters will be determined by making an empirical relation between the seismic moment and maximum displacement amplitude of the S-wave.
How to cite: Jafari, S., Ertuncay, D., Fornasari, S. F., Cataldi, L., Pazzi, V., and Costa, G.: Empirical Attenuation Characteristics and Seismic Source Parameters through Spectral Inversion for Northeastern Italy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17578, https://doi.org/10.5194/egusphere-egu25-17578, 2025.
Ground response (GR) refers to the amplification and damping of seismic wavefield components under linear and nonlinear elastic conditions. While seismic waves are the primary triggers of GR, other dynamic phenomena, such as explosions and strong acoustic waves, can also induce GR once they couple into the ground. In volcanic environments, natural explosions frequently interact with unconsolidated near-surface materials, making GR a critical factor in assessing volcanic hazards.
To investigate GR in such contexts, we selected Mt. Etna as a study site due to its persistent volcanic activity, which generates a wide frequency range (0.01–100 Hz) of seismo-acoustic signals. Additionally, Mt. Etna features complex ground structures, such as faults, dykes, and unconsolidated scoria deposits, making it an ideal natural laboratory for examining GR phenomena. In 2019, a multi-parametric network was deployed near its summit crater, comprising broadband seismometers, infrasound sensors, and a buried fiber optic cable (30 cm depth) for distributed dynamic strain sensing (DDSS).
We compiled a catalog of over 8,000 volcanic explosions. Our observations reveal emergent high-frequency (10–50 Hz) acoustic waves embedded within the low-frequency signals of the explosions. These high frequencies are amplified when the explosions couple into the scoria material of the deposit, as evidenced by the DDSS and broadband seismometer data.
To characterize the local response of the near-surface material during air-to-ground coupling of the explosions, we analyzed stress-rate vs. strain-rate relationships derived from peak-to-peak (p-p) amplitudes of GR signals and classified explosion events. Explosions were classified using waveform similarity, while GR in the DDSS signals were classified using a modified approach that incorporates both temporal and spatial dimensions. These relationships reveal hyperelastic behavior of the scoria material, described by three distinct and consecutive elastic stages: linear, softening, and stiffening.
The hyperelastic curves enable the extraction of key elastic parameters, which we use to model GR at Mt. Etna with waveform propagation codes employing lattice methods. We validate this approach by estimating Vp velocities from elastic parameters and comparing them with direct Vp measurements from tap test on the fibre optic cable. Preliminary modeling results demonstrate the potential of lattice methods to capture the nonlinear dynamics of geomaterials and provide deeper insights into the elastic parameters influencing GR. These findings underscore the importance of incorporating GR into volcanic hazard assessments and enhance our understanding of near-surface material dynamics in volcanic environments.
How to cite: Diaz-Meza, S., Jousset, P., Currenti, G., Costes, L., and Krawczyk, C.: Nonlinear ground response due to air-to-ground coupling of volcanic explosions; a study case from Mt. Etna volcano, Sicily., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18598, https://doi.org/10.5194/egusphere-egu25-18598, 2025.
In tectonically active regions, surface faulting and offset of the ground surface caused by capable faults pose significant hazard to urban settlements and critical infrastructures. Given the challenges in fully parametrizing the geometry, kinematics, and activity of a capable fault, Probabilistic Fault Displacement Hazard Analysis (PFDHA) is widely employed. PFDHA is a relatively recent methodology that estimates the probability and magnitude of expected surface displacement at a given site during an earthquake.
Current methods for Fault Displacement Hazard Analysis (FDHA) are commonly tailored to specific kinematic scenarios and often rely on scaling laws that are based on the characteristic earthquake magnitude. These approaches typically distinguish between displacements occurring along the primary fault (PF) and those occurring at distributed off-fault ruptures (DR). However, only a limited number of these methods are associated with computational tools, and their accessibility to users varies widely.
This study introduces a new Matlab-based tool that integrates published scaling laws, surface rupture models, and fault displacement models into a PFDHA framework. The tool supports hazard assessment for both PF and DR displacements and incorporates the concept of floating rupture along faults, a common practice in probabilistic seismic hazard assessment.
The modular design of the code provides users flexibility in generating hazard curves and maps by allowing them to select a variety of kinematic-specific components within the PFDHA. Furthermore, it allows the hazard assessment that considers distinct frequency-magnitude distributions.
Moreover, a novel approach to address co-seismic ruptures that may be shorter than the total length of the main fault is proposed. It involves translating fault segments along the fault trace, with the co-seismic rupture length evaluated over a range of Mw values, such as those derived from a truncated Gutenberg-Richter distribution. The conditional probability of exceedance is then determined by recalculating the x/L points corresponding to the site location (x) in each rupture length (L) translating along the total length of the fault. Contributions from all scenarios are aggregated to produce the total hazard for distributed ruptures.
This new tool aims to advance the current state of PFDHA by addressing variability among current models, facilitating direct comparisons between published methodologies for both PF and DR.
How to cite: Bonini, S., Scotti, O., Valentini, A., Visini, F., Tartaglia, G., Asti, R., and Vignaroli, G.: A new Matlab tool to assess probabilistic fault displacement hazard, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18872, https://doi.org/10.5194/egusphere-egu25-18872, 2025.
Only the first level of seismic microzonation (SM1), performed in 2016, is available for the city of Trieste. A seismic noise measurements campaign was conducted in the municipality during 2022 in the different homogeneous microzones in the seismic perspective (MOPS), defined by SM1.
The main purpose was to verify the behaviour within each MOPS, and the results have shown that the hypothesis of a homogenous microzone is not always verified: in many cases, high behavioural variability was found within the same. Therefore, MOPS seem to be a good tool for general first-level evaluation, but they do not appear to be accurate enough for detailed site-effect evaluation. A recent study demonstrated that second-level microzonation national abacuses (MS2) are not applicable in the Friuli Venezia Giulia Region since, being a simplified method, they underestimate the site response.
For this reason, a new urban accelerometric seismic network was implemented in Trieste with the purpose of seismic monitoring and to evaluate the site effects which have been validated using numerical simulation.
How to cite: Parentelli, F., Beltrame, C., Fornasari, S. F., Pazzi, V., Moschion, G., and Costa, G.: Urban seismic network development for site effects evaluation in Trieste , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19491, https://doi.org/10.5194/egusphere-egu25-19491, 2025.
How to cite: Frucht, E., Kamai, R., and Biran, G.: Enhanced Vs30 Prediction Models: Leveraging Geology and Terrain with Machine Learning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21127, https://doi.org/10.5194/egusphere-egu25-21127, 2025.
How to cite: Hakimov, F., Havenith, H.-B., Ischuk, A., and Reicherter, K.: Numerical modeling approach to support the future seismic microzonation of Dushanbe, Tajikistan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21168, https://doi.org/10.5194/egusphere-egu25-21168, 2025.
Seismic data analysis plays a crucial role in understanding ground structures and informing earthquake engineering applications. The study area, the Eskişehir Basin, is one of Turkey's most important agricultural and industrial regions. As population density and settlements in this region rapidly increase, knowledge of ground structure and earthquake risk assessment become critical. The basin is surrounded by highlands in the north and south and exhibits a flat plain character in its central part. The Nakamura's H/V technique and the Spatial Auto Correlation Method (SPAC) were employed to jointly evaluate the seismic behavior of different ground types using inverse solution and obtain S-wave velocity-depth profiles and determine the engineering bedrock depth at the measurement points. The evaluation revealed an average bedrock depth of 136 meters, an average bedrock depth velocity of 552 m/s, and Vs30 velocities ranging between 360 m/s and 400 m/s across the measurement points, with an average of 384 m/s. The findings indicate that the Eskişehir Basin's ground structure exhibits significant variability. Variations in bedrock depths and velocity suggest that seismic risk across the city's different regions also varies. This information can be utilized for urban planning, earthquake-resistant building design, and disaster risk reduction efforts.
How to cite: Arslan, M. S. and Özel, A. O.: Joınt Inversıon Of H/V And Spac Methods: A Case Study Of Eskişehir Basın, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-771, https://doi.org/10.5194/egusphere-egu25-771, 2025.
Posters virtual: Mon, 28 Apr, 14:00–15:45 | vPoster spot 1
EGU25-5076 | Posters virtual | VPS21
Active and capable faults (FAC) and buildings in Norcia, interventions carried out and possibile technicolor and regulatory actions.Mon, 28 Apr, 14:00–15:45 (CEST) | vP1.13
How to cite: Motti, A.: Active and capable faults (FAC) and buildings in Norcia, interventions carried out and possibile technicolor and regulatory actions., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5076, https://doi.org/10.5194/egusphere-egu25-5076, 2025.
EGU25-16647 | Posters virtual | VPS21
Characterization of selected “rock” reference stations of the Hellenic Accelerometer Network (HAN)Mon, 28 Apr, 14:00–15:45 (CEST) | vP1.14
In Greece, almost all accelerometer stations provided accelerometer recordings, more than 400 in total, are characterized by inferred Vs30 values based on combination of surface geology and slope proxy (Stewart et al. 2014). However, only about 15% of them have been characterized by in-situ geophysical and geotechnical methods (invasive or/and non-invasive) were performed at a distance less than 100m from the station. In addition, regarding reference rock stations where shear wave velocity Vs30 is equal or greater than 800m/sec (engineering bedrock), only five (5) of them have been characterized todate, with respective values ranging between 800Vs301183m/s. It is evident that measured site characterization parameters of accelerometer stations in Greece is far from a desired goal, especially regarding those on rock reference sites. In this study multiple/combined non-invasive passive and active seismic techniques are applied in six (6) accelerometer stations throughout Greece, to improve earthquake site characterization metadat of the national accelerometer network, focusing on stations placed on geologic rock conditions. The Vsz (S-wave) and Vpz (P-wave) profiles and thereby Vs30 site class according to the Eurocode-8 are determined. In addition, to form a holistic picture of the site’s characterization, surface geology and topographic properties are provided for the investigated stations. Results of this study aim at contributing on improving site characterization parameters estimated by the Generalized Inversion Technique (source, path, site), as well as in defining Ground Motion Models for rock site conditions.
How to cite: Theodoulidis, N., Hollender, F., Rischette, P., Buscetti, M., Douste-bacque, I., Grendas, I., and Roumelioti, Z.: Characterization of selected “rock” reference stations of the Hellenic Accelerometer Network (HAN), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16647, https://doi.org/10.5194/egusphere-egu25-16647, 2025.
EGU25-3782 | Posters virtual | VPS21
Influence of paleochannels on liquefaction effects in the cities of Chone and Portoviejo (Ecuador) following the strong Pedernales earthquake in 2016Mon, 28 Apr, 14:00–15:45 (CEST) | vP1.17
A strong earthquake with a magnitude of Mw 7.8 and a nearby epicenter in the city of Pedernales, Ecuador, occurred on April 16, 2016. This seismic event severely affected several cities in Ecuador, including Chone and Portoviejo, both in the Manabí province, located some 85 km and 150 km away from the hypocenter, respectively. In Chone, a total of 662 homes were damaged, while 2,678 collapsed dwellings were registered in Portoviejo, where 137 fatalities were reported. These, like most cities in the Manabí province, were built in narrow valleys over colluvial and alluvial soils. The thickness of these sediments in contact with the rock is between 40 and 70 meters, which corresponds to both ancient and contemporary alluvial plains that are supported by alluvial-colluvial and alluvial valley-fill deposits. After the 2016 interplate subduction earthquake, the main co-seismic geological effects were reported for constructions built on these soils. Landslides were primarily documented in the colluvial soils, while soil liquefaction effects were reported in soft and loose soils. In this research, the influence of the presence of paleochannels in both cities, Chone and Portoviejo, on the liquefaction effects reported during the seismic event is analyzed.
The Chone River flows through Chone city from east to west, while its western part was modified after 1975, leaving an abandoned meander where the river channel was between 7 and 22 meters wide. The soil profile in this area demonstrates a low percentage of fines, ranging from 15 to 52%, with a relative density of about 50%, making it susceptible to liquefaction. After the 2016 earthquake, evidence of liquefaction effects was concentrated along the old meander. The Portoviejo River, which flows through the city of Portoviejo, has changed from a pronounced meandering shape in 1911 to its current form. This change spans about 4.5 km with a low slope between 0.1 and 0.2%. The width of the river has also been reduced, from 12 to 19 meters. The analysis of the liquefaction evidence indicates that the damage was very severe, especially in the constructions along the river.
The damage inventories performed in both cities have evidenced that paleochannels exhibited several signs of soil liquefaction. The geological and geotechnical conditions of these soils, such as size distribution, shallow groundwater table and recent-age deposits, may be considered as factors potentially increasing the probability of liquefaction. Therefore, a geomorphological study of the cities can help identify areas with a higher liquefaction potential.
How to cite: Pastor, J. L., Ortiz-Hernández, E., Toulkeridis, T., and Chunga, K.: Influence of paleochannels on liquefaction effects in the cities of Chone and Portoviejo (Ecuador) following the strong Pedernales earthquake in 2016, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3782, https://doi.org/10.5194/egusphere-egu25-3782, 2025.
