This session aims to gather multidisciplinary contributions that bridge the fields of seismology geology, geotechnics, and engineering and will focus on the following topics:
- Site characterization and seismic microzonation;
- Empirical assessments of stratigraphic and topographic amplification effects;
- Quantitative evaluation of seismic site response in 1D, 2D, and 3D configuration;
- Earthquake-induced ground effects, such as landslides, liquefaction and cavity collapse;
- Soil-structure interaction and characterization of building response to seismic events;
- Proposals for integration and/or revision of building codes;
- Analysis of historical and cultural heritage sites.
The session also aims to collect results based on different geophysical techniques (e.g., earthquake data, ambient noise analysis, HVSR, array measurements, active surface wave prospecting, ERT, GPR, seismic refraction tomography, etc.) and their integration. Contributions regarding innovative methodologies as Distributed Acoustic Sensing (DAS) systems and dense arrays are well accepted.
Orals: Mon, 28 Apr | Room 1.15/16
The study of the occurrence and incidence of environmental coseismic phenomena is becoming an increasingly demanding and fundamental need for the seismic hazard evaluation and risk reduction. Landslides triggered by earthquakes are the most diffuse environmental phenomena and can cause significant long-lasting impacts and losses across the area affected by the earthquake shaking. The combination of the relatively frequent seismic release with a very high landslide susceptibility, makes the Italian territory especially prone to the occurrence of earthquake-induced landslides.
The CFTIlandslides (https://cfti.ingv.it/landslides/) is a recently released database of historical earthquake-induced landslides (HEILs) in Italy that includes over 1,000 landslides associated with 140 seismic events. The data are collected from the review of historical sources and the analysis of scientific articles and technical reports and are geographically localized in a GIS environment comparing the historical information with modern topographic datasets and the Italian national inventory of landslides (IFFI database: https://www.progettoiffi.isprambiente.it). Based on these criteria CFTIlandslides is currently the only historical dataset available at a global, regional, and national scale.
The CFTIlandslides was designed as continuously updated repository, and as such it is open to later additions and improvements in future releases. The first version of the database features historical earthquake-induced landslides subdivided into classes based on location accuracy and type of movement.
The CFTIlandslides is conceived as a publicly accessible online WebGIS, it has interactive access to external data via web-services. This allows to visualize and compare HEILs localization with other geophysical and geological information. Data can be analyzed using a 3D terrain map. Moreover, the CFTIlandslides data are distributed through OGC web services, and can be downloaded in different file formats.
The HEILs collected in the CFTIlandslides can be used to:
- to develop empirical relationships between landslide density and seismological parameters of the triggering earthquakes at national and regional scales;
- make comparison between earthquake-induced landslides distribution of past and recent earthquakes;
- perform detailed historical studies of a single landslide or a specific area.
Therefore, this new dataset is the starting point for new elaborations about the study of earthquake-induced landslides. These results can subsequently be applied to mitigate seismic hazards and reduce risks and build effective strategies for urban planning and emergency management.
The database is addressed to a large audience of potential users and stakeholders, including researchers and scholars, administrators and technicians of local institutions, and civil protection authorities.
How to cite: Zei, C., Tarabusi, G., Ciuccarelli, C., Burrato, P., Sgattoni, G., Taccone, R. C., and Mariotti, D.: The CFTIlandslides, Italian database of historical earthquake-induced landslides, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4015, https://doi.org/10.5194/egusphere-egu25-4015, 2025.
Following previous studies that identified a potential correlation of the subsidence rates of the soils with the sediment thicknesses (Hbed), or with the resonance periods of the soil columns (T0), we want to verify this correlation in the urbanised valley of Grenoble (French Alps) prone to significant lithological site effect. We take advantage of the high level of geophysical and geotechnical characterisation of this basin to develop a new strategy to estimate site-effect parameters based on subsidence rates measured by satellite Persistent Scatterer InSAR (PSI). Since May 2022, the European Ground Motion Service (EGMS) delivers open-access maps of subsidence rates in high spatial resolution (up to one point every tens of meters) and releases a new dataset every year. Our study aims in particular at testing the feasibility with EGMS data to correlate the soil subsidence rates with the site-effect parameters in the Grenoble basin.
A strong advantage of the subsidence-rate data lies in their high spatial resolution, that, for example, we could exploit in microzonation studies. However, the subsidence-rate data also presents two mains drawbacks. First, the measurement points of subsidence rate do not all have the same quality, due to uncertainties in the PSI method employed by EGMS. Second, when comparing different EGMS updates, the subsidence rates vary from one release to another because of changes in the data referencing applied by EGMS, which causes difficulties to define a site-effect model independent of the EGMS updates. To overcome these two drawbacks, we define a specific protocol to filter and process the subsidence rates in order to obtain a single model of prediction for each site parameter studied, and independent of the chosen EGMS release.
We show that in the Grenoble basin and outside of anthropogenic sources such as water pumping, the subsidence rates are only correlated with site parameters sensitive to properties of the whole soil columns (sediment thickness Hbed and fundamental resonance period T0) and not with surface parameters (VS30, geological facies at the near surface, building weights). This suggests that the subsidence rates as measured by satellite PSI are mostly caused by the compaction of the stiff and thick sediments due to their own weight. We finally conclude by quantifying the accuracy and the reliability of the obtained prediction models, in order to assess the input of the PSI satellite data for high-resolution site-effect assessment in urbanized valleys.
How to cite: Schindelholz, V., Cheaib, A., Maufroy, E., Cornou, C., and Pathier, E.: Using the soil subsidence from satellite Persistent Scatterer InSAR (PSI) to estimate site-effect parameters in high spatial resolution, case of the sedimentary basin of Grenoble (French Alps)., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10894, https://doi.org/10.5194/egusphere-egu25-10894, 2025.
How to cite: Jagodnik, V. and Sulovsky, T.: Cyclic Shear-Induced Degradation in Saturated Uniform Sands at Small Strains, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15825, https://doi.org/10.5194/egusphere-egu25-15825, 2025.
The significance of local site effects in seismic hazard assessment is well-recognised. However, nonlinear soil behaviour during high-strain conditions is often neglected or oversimplified, even for large return periods. This study aims to estimate the impact of nonlinearity and liquefaction on the local seismic hazard using the multistep approach by Janusz et al. (2024), in particular in low-to-moderate seismicity areas, where nonlinearity is not instrumentally observed and hence particularly difficult to assess. We focus on sites in Switzerland, where strong earthquakes are relatively rare, although documented in the past. An exemplary area is the subalpine sedimentary basin of Lucerne, which is vulnerable to nonlinearity and liquefaction because of soft alluvial deposits (VS30<300 m/s) and a shallow water table depth (~1–4 m).
Typically, simplified linear equivalent models are used for modelling nonlinearity. Here, we use fully nonlinear numerical estimators with a constitutive model that accounts for pore pressure excess development, allowing for simulating the dilatant behaviour of the soil and indicating the onset of liquefaction. Moreover, the soil models are often characterized either using generalised values from literature or expensive laboratory measurements, which may not reflect in-situ conditions. We use soil models calibrated using cone penetration tests (CPT), which are in-situ geotechnical surveys, allowing for site-specific assessment.
Our findings show that the impact of the nonlinear soil behaviour cannot be neglected even in low-to-moderate seismicity areas like Lucerne. In the case of a strong shaking consistent with the local seismic hazard for 475 and 975 years return periods, we observe the high impact of the nonlinearity such as increased damping leading to a decrease of the site amplification. Moreover, due to nonlinearity, the soil resonance frequencies shift towards lower values, which may affect the risk estimation for some buildings. Additionally, in our simulations, strong deformation is induced in some sandy layers due to the rapid build-up of the pore pressure, with a high possibility of liquefaction. However, the variability between tested sites is significant, indicating that nonlinear site response is highly site-specific, and hence, a reliable characterization of the soil profile is crucial. Even though we observe some similarities between sites of the same soil class and characterized by similar properties e.g. water table depth, the correlations are highly dispersed. Furthermore, we explore the uncertainty and sensitivity due to the model parameters and the input ground motions.
The current work concentrates on verifying the results using strong-motion recordings with nonlinear observations, which are currently lacking in Switzerland. The indirect comparisons with empirical data from Japanese sites show similar trends and values. For direct validation, we aim to apply the procedure using the CPT-calibrated soil models from Wellington (New Zealand), where nonlinearity was observed during the 2016 Mw 7.8 Kaikōura earthquake.
This study was part of the Horizon 2020 ITN-funded URBASIS-EU and the ENSI-“Seismological research for Swiss nuclear facilities” project.
Janusz P, Bergamo P, Bonilla LF, et al (2024) Multistep procedure for estimating non-linear soil response in low seismicity areas—a case study of Lucerne, Switzerland. GJI, 239:1133–1154. https://doi.org/10.1093/gji/ggae324
How to cite: Janusz, P., Bergamo, P., Bonilla, L. F., Manea, E., Hill, M., and Fäh, D.: Simulating site-specific nonlinear site response in low-to-moderate seismicity areas – insight from Switzerland, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8822, https://doi.org/10.5194/egusphere-egu25-8822, 2025.
The dynamic non-linearity behavior affecting soils during earthquakes is a critical factor that can significantly influence seismic response, particularly when combined with site effects. Understanding this phenomenon is essential for seismic risk mitigation, especially in areas with active tectonics like the Central Apennines valleys, including the Norcia basin, which is the focus of this study. These flat areas often host industrial and historical urban centers, which increases the need for effective seismic risk reduction strategies.
This research aims to investigate the effects of non-linearity on site response in valley areas using both 1D and 2D dynamic numerical models along a section passing through Norcia city. Different seismic signals with increasing PGA values are used in modeling to test the model under varying levels of seismic stress and simulate the achievement of non-linear dynamic behavior. Two main goals are in fact pursued: to examine how site response varies depending on location within the basin and to investigate the effect of increasing Peak Ground Acceleration (PGA) on site response.
The first result of this work is been the creation of a robust geological subsurface model for the Norcia basin for subsequent numerical modeling. Previous studies carried out on the area show disagreements about the dominant site effects and the geological model of the subsurface. None of them provided a detailed discrimination of the seismic layers within the basin fill. After a review of previous data and elaboration of new data acquired, a calibration of the model using the Generalized Inversion Technique (GIT) is performed. This process has allowed to refine geometric and parametric details and defining a non-homogeneous basin. This process also led to a revised identification of the geological and seismic bedrock, emphasizing the importance of distinguishing between these two layers.
Twenty-five 2D numeric simulations are run, with the same number of different seismic inputs, selected from the Italian accelerometric database. The PGA values ranging from 0.03g to 0.36g. The medium frequency range of the signals (low, medium, and high) is also considered. Several control columns are extracted along the section and performed also in 1D simulations. More than 400 surface accelerograms are analyzed to obtain response spectra and compare 1D and 2D models trough the basin.
The results of the study are showed in terms of the aggravation factor (AG) and the Valley Amplification Factor (VAF) and allow a deeper understanding of their relationship with the PGA, aspect that recent definitions of these factors still do not account for.
How to cite: Caciolli, M. C., Barchi, M. R., De Franco, R., Giallini, S., Mancini, M., and Pagliaroli, A.: Evaluation of non-linear valley effects through numerical modeling: the case of Norcia (Italy), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19727, https://doi.org/10.5194/egusphere-egu25-19727, 2025.
ASCE/SEI Standard 7-22 is in progress for adoption by countries, states, municipalities around the world in 2025. Chapter 20 describes new standards for determining seismic site class that encourage geophysical surveying rather than cone penetrometer or standard penetration testing. Invasive methods can fail to achieve compliance because of refusal or difficulty for intrusive methods to access sites. For non-intrusive geophysical surveying to achieve code compliance it is important for geotechnical engineers to employ geophysical survey methods effective at determining the time-averaged shear-wave velocity from the surface to 30 m depth, known as Vs30. Without such measurements, taking the default seismic site class may lead to over-design of building structures, inflated construction costs and extended project timelines. Code allowance of seismic surface-wave-arrays offers engineers the opportunity to perform one geophysical survey yielding Vs30 and site class along with a more comprehensive site investigation including assessments of the critical zone, depth to bedrock, fault location, and even P-wave velocity and Poisson’s ratio. ASCE 7-22 compliant surface-wave surveys, when processed and interpreted with Terēan software, will provide this full range of results. Most sites require less than one hour to complete for Vs30 measurement, including narrative report generation. This technology increases the ease of data collection with an untethered, triggerless hammer and the ability for the same array of 24, 4.5 Hz geophones to collect S- and P-wave data simultaneously, and simplifies seismic data acquisition by eliminating the need for hammer cables and surveying. Many case histories at scales from 5 m to 1000 m serve to demonstrate these rapid and comprehensive results, including assessments of basin structure to kilometer depths. Simpler geophysical surveys with more comprehensive results allow engineers and geologists to more efficiently complete safety and environmental assessments.
How to cite: Louie, J., Starr, A., and Honjas, B.: Simplified Seismic Surveys for Non-Intrusive ASCE 7-22 Compliant Site Class, Critical-Zone Characterization, Fault Location, and Basin Structure, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7646, https://doi.org/10.5194/egusphere-egu25-7646, 2025.
Between May and September 2023 we recorded the environmental seismic vibrations in the archaeological area of the Circus Maximus (Rome, Italy) before, during and after four live concerts of Italian and international musicians: Springsteen, Mengoni, Scott and Pezzali (an audience of around 70,000 people for each concert).
The Circus maximum is an ancient Roman chariot-racing elliptical shaped stadium (621 m x 118 m) whose first construction dates back to 329 BC. At present, the main structure of the stadium is buried under a green lawn, which is open to the public, and only on the south-eastern side the structure of the hemicycle can be seen. It is here that the archaeological area, managed by the Sovrintendenza Capitolina, is separated and protected from the public area by a metal fence. Apart from the Roman ruins, in this area there is also a 3-floors medieval tower - known as Torre della Moletta - placed at about 500 m away from the main stage.
The concert stage is located at the north-western tip of the Circus Maximum area, facing south-east towards the archaeological area, at a distance of less than 500 metres from the tower. Here, as well as in other points of the archeological area, we were asked to install some seismometers during the concerts, being the archeologists worried about the observed oscillations of the Tower during previous live shows.
For all concerts, we deployed one seismic station on the top and one on the bottom level of the Tower, and some other seismic stations in the surrounding archeological area. The equipment used consisted of six-channels high-resolution digitizers (i.e. with velocimeter and accelerometer sensors) or nodal stations. Among the four concerts, the live show of Travis Scott was the one with the highest amplitude level; the seismic signals were almost entirely clipped during the performance. Many alarmed Roman citizens claimed to have felt an earthquake for the vibrations caused by the concert.
In this study we present the analysis of the environmental vibrations recorded before, during and after the concerts, in terms of velocity and acceleration time series, spectral analysis and variation of the resonance parameters of the Tower. In particular, even if the emitted sound should be focused at frequency beyond 20 Hz, the spectrograms clearly highlight very distinct frequencies related to each song also in the seismic bandwidth (1-5 Hz). This effect can be both due to the transmission of the sound waves to the soil but also to the dancing and jumping of the public during the songs. Before the Scott concert, the Tower had a resonant frequency peaking at about 3 Hz. After the Scott concert, the resonant peak drops by about 0.2 Hz, as confirmed by the subsequent observation for the Pezzali concert.
How to cite: Bordoni, P., Cara, F., Famiani, D., Di Giulio, G., Milana, G., Pucillo, S., Riccio, G., Vassallo, M., Hill, C., and Doglioni, C.: The seismic monitoring of a medieval tower in the Circus Maximus (Rome, Italy) during pop and rock concerts, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19229, https://doi.org/10.5194/egusphere-egu25-19229, 2025.
For decades, both qualitative and quantitative observations of earthquake intensities have highlighted the impact of surface geology on the characteristics of the ground shaking. However, site effects are often inadequately incorporated into seismic risk assessments. Many hazard and risk models simplify the consideration of site effects by using average soil properties in the upper 30 meters (Vs30), even though this approach neglects the influence of entire basins, as well as additional factors such as lateral heterogeneities, geomorphological features, and topographic properties of the landscape.
While various proxies have been developed to streamline the estimation of site effects with high accuracy, the adoption of site-response proxies based on Vs30 over the past two decades favoured practicality over rigorous validation. These generic proxies, often embedded in seismic codes, are often not subjected to thorough evaluations. In this study, we investigate how the use of simplified approaches impacts on earthquake loss assessments.
We evaluated over 20 approaches for modelling site effects, incorporating diverse proxies, methodologies, and geographical scales. Assuming seismic zonation studies (SZS) as the most accurate methodology and the benchmark, we conducted probabilistic risk assessments for five cities in Colombia, with varying geological conditions and seismic sources. These case studies utilized detailed exposure models and SZS-derived amplification functions at different intensity levels, integrating geotechnical, geophysical, and geological characterizations validated through numerical modeling and seismic records from local and national networks.
Our findings indicate that while the geographical resolution of the soil parameter used as a proxy (e.g Vs30) used to estimate site effects has limited impact on risk metrics, the chosen methodology significantly influences results. Additionally, consistent with previous hazard studies, we observed that incorporating the non-linear behavior of soil is crucial to avoid overpredicting the impact. These conclusions were derived from comparative analyses of risk metrics, including risk curves for return periods up to 1,000 years and annual average losses.
Based on our results, we offer two key recommendations for earthquake risk modelers:
- To focus not only on improving spatial resolution of soil parameters used as a proxy to assess site effects but also on validating amplification values using local data and numerical modeling, as this step critically shapes the final outcomes.
- Evaluate site effect approaches on a case-by-case basis, as simplified models fail to fully capture the complexities of soil response, leading to varying degrees of over- or underprediction.
How to cite: Montejo, J., Silva, V., Pace, B., and Pagani, M.: Influence of site effect modelling approaches in seismic risk assessment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5736, https://doi.org/10.5194/egusphere-egu25-5736, 2025.
VS30 is a widely used parameter for characterizing local site conditions. A VS30 map serves as a fundamental dataset for various studies related to seismic hazard assessment and seismic risk mitigation. In China, over 30 years of extensive engineering projects have generated a wealth of borehole-based VS measurements. We complied a site profile dataset containing tens of thousands of borehole profiles derived from over 3,000 site investigation reports associated with engineering projects across mainland China, covering all provinces and over 200 major cities. To better utilize this abundant site data for developing a VS30 map for China, we proposed a Cokriging-based VS30 proxy model (SCK model) in 2022 that uses VS30 measurements as constraints and topographic slope as a secondary variable, producing the first version of the VS30 map for mainland China. In 2024, we refined the SCK model by: (1) explicitly accounting for the influence of surrounding topographic slopes rather than only the slope at a single point, (2) incorporating more distant VS30 measurements, and (3) improving the spatial distribution of VS30 measurements used in the model calculation. Additionally, we added new VS30 data from China strong-motion stations to enhance data coverage in western China. Using the refined SCK model and the expanded VS30 data set, we developed the 2024 version of VS30 map for mainland China. This map is constrained by 7,939 VS30 measurements, features a grid resolution of 30 arcsec (approximately 900 m), and demonstrates reduced estimation errors with improved spatial continuity. Compared to the China part of the USGS Global VS30 Mosaic, our map provides more plausible results due to its use of local data constraints and its better reflection of the geological and geomorphological characteristics of China. The 2024 version of the VS30 map for mainland China is available as an open-access dataset to support further research and practical applications. We are currently working on incorporating surface geology and depositional environment as additional parameters to further enhance the SCK model’s performance and the map’s ability to reflect local site conditions.
How to cite: Zhou, J., Li, L., Li, X., Xi, N., Tian, X., Chen, K., and Xu, G.: VS30 Map for Mainland China Constrained by Local VS30 Measurements and Incorporating Topographic Slope as Secondary Data via a Cokriging (SCK) Model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15946, https://doi.org/10.5194/egusphere-egu25-15946, 2025.
The performance of the built environment during earthquakes is strongly influenced by local and regional variations in ground conditions that influence the amplitude and frequency content of ground motions. Developing models to predict these local site amplification effects is a key ingredient for the modelling of seismic hazard and risk. This study investigates the capability of various measured site parameters (e.g., fundamental frequency (f0)/period (T0), HVSR) and/or inferred site proxies (e.g., slope, rock classification, curvature) to predict local site amplification in New Zealand (NZ). To achieve this, we compiled an extensive database of relevant site parameters at 582 GeoNet seismic stations, derived from seismic data (ambient noise and earthquake recordings), geological and topographical maps, as well as site parameters included in the NZ-strong-motion database (Wotherspoon et al., 2024). Additionally, the NZ backbone model proposed by Atkinson (2024) was used to compute PSA site-to-site variability within the period range of 0.05 to 10 seconds, utilizing a comprehensive dataset of ground motion parameters from Manea et al. (2024). We then evaluated the robustness of correlations between site parameters and earthquake site-to-site variability to assess their performance both individually and in combination.
The results indicate that of any single metric, the strongest correlation with site-to-site variability is achieved by geological era, closely followed by site classes based on the 2004 NZ seismic design standard (SNZ 2004). Among measured parameters, VS30 shows the best performance at short periods, while T0 is more effective at longer periods. Conversely, Z1.0 and Z2.5 exhibit the lowest coefficients of determination, perhaps either reflecting the poor characterisation of these parameters, or implying that bedrock characteristics in NZ differ from those in regions where these parameters were originally developed. Inferred parameters such as slope, curvature, and relief perform similarly, although they may capture different aspects of site-to-site variability. In conclusion, while different geological and topographical proxies are effective for estimating site amplification at a regional scale, measured site parameters such as the fundamental frequency/period, VS30 and HVSR are also needed to capture the variability of site response at the local level.
How to cite: Manea, E., Kaiser, A., Wotherspoon, L., Stolte, A., Hill, M., and Gerstenberger, M.: Estimating Site Amplification in New Zealand Through Measured and Modeled Proxies, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13322, https://doi.org/10.5194/egusphere-egu25-13322, 2025.
The characterization of the soil properties at seismic stations is extremely important for all the studies related to seismic network data. On the other hand, the availability of such a large dataset of site indicators offers the possibility to look for statistical correlations between different site indicators. In the framework of the 2022-25 PRIN-SERENA project (“Mapping seismic site effects at regional and national scale”, granted by Italian Ministry of University and Research), we use the information archived in the CRISP database relating to the site characterization of more than 400 stations belonging to the Italian Seismic Network (http://crisp.ingv.it/).
We first analyze the distribution of the most significant indicators with large sample size: Horizontal-to-Vertical spectral ratio on both noise and earthquakes (HVSR), lithological classification, site and topography classes from national and european building codes. We then consider the HVSR as a reference proxy of site effect estimation at the stations sites and we look for relations with the others indicators. The cluster analysis of the HVSR curves highlights that about half of the stations have amplitudes reaching, on average, values of 4. They can also be grouped in four different shapes: flat curve (sites without HV amplification), amplification in the low-to-intermediate (f<2-3 Hz) and in the high (f>2-3 Hz) frequency ranges, large amplification for frequencies from about 1 to 3 Hz. Moreover, the mean HV curves from noise maintain values lower or similar to those from earthquakes, whereas single noise peaks have greater amplitudes.
A not straightforward correlation with the other proxies is clearly recognizable, except a weak but significant dependence with the lithology and soil classes: the resonance frequency decreases as the soil characteristics deteriorate, and its amplitude slightly increases as the site characteristics degrade. The comparison of the results with the site correction term of the Local Magnitude shows that the combination of these two conditions causes an overestimation of the magnitude computation at about 10% of the seismic stations.
How to cite: Cultrera, G. and Mercuri, A.: Statistical analysis on soil response of the Italian Seismic Network from the CRISP database, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6773, https://doi.org/10.5194/egusphere-egu25-6773, 2025.
In the framework of an Italian research project (2022-25 PRIN SERENA “Mapping Seismic Site Effects at Regional and National Scale”, granted by the Italian Ministry of University and Research), we aimed at the empirical verification and calibration of the numerical ground-motion amplification maps developed within the project, using in-depth geological, geophysical and seismological information. For this purpose, a database of experimental site-specific amplification estimates (AFs) in three interval periods was created for more than 1900 sites, both at national scale (permanent and temporary seismic networks) and for selected areas (Central Italy, North-East Italy, Basilicata region, Ferrara).
Three different approaches were used to compute the AFs: i) spectrum-compatible accelerograms (Uniform Hazard Spectrum) as input and amplification function from Generalized Inversion Technique (GIT) applied to input motion (Fourier spectrum, FAS, or Response spectrum, SA); ii) estimate based on the repeatable site-to-site terms of a reference Ground Motion Model in SA for the EC8-A class; iii) both input and output computed from recordings at the reference station and at the target one (SSR). A GIS architecture was developed for storage and to perform semi-automatic comparisons between experimental estimates themselves and with the numerical ones using JupyterLab (web-based interactive development environment).
The comparison of AFs from different techniques highlights that experimental estimates are well-correlated in the investigated areas, with better agreement between integral parameters (FA), and that the observed differences with the GIT or SSR estimates are due to the dependence on the reference site and on the choice of earthquake catalogue.
How to cite: Hailemikael, S., Cultrera, G., Peloso, A., Martini, G., Barnaba, C., Laurenzano, G., Lanzano, G., Sgobba, S., and Gallipoli, M. R.: Empirical estimates of Site Amplification Factors in Italy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7487, https://doi.org/10.5194/egusphere-egu25-7487, 2025.
Predicting ground motion over large areas seems to be the frontier in the enhancement of seismic hazard maps at the national level. Simplified approaches based on 1D numerical simulations have gained traction due to the limited availability of detailed geological and geotechnical data. The Italian Project PRIN-SERENA (mapping Seismic site Effects at REgional and National scAle) aims to improve ground motion amplification maps by deriving site-specific amplification functions (FAs) through numerical modelling and validating these models against experimental data to ensure reliability and practical applicability.
In the framework of WP6-SERENA project, we evaluated the suitability of these simplified methods in 21 seismic stations located an intermontane basin in the southern Apennines (Val d’Agri, southern Italy), characterised by high seismicicity and complex geology. The amplification functions (FA) were experimentally estimated by applying a nonparametric single-step generalized inversion (Klin et al., 2018) to a database of about 2000 waveforms from local and regional events (up to 400 km), providing robust azimuthal coverage for each station.
For the 21 sites experimental FAs were estimated for three period bands of engineering interest: 0.1 – 0.5 s, 0.4-0.8 s and 0.7-1.1 s. These estimates were compared with those derived from the 1D stochastic modelling results by using the NC92soil software (Acunzo et al., 2024) and the subsurface seismo-stratigraphic and mechanical models as input data. The modelled FAs exhibited a narrow amplification range (0.7-1.5), while experimental FAs showed a broader range (1-5). Sites that have the same stratigraphic and mechanical subsurface model have identical modelled FAs, while experimental FAs have very different values reflecting the actual geological complexity of the sites. This discrepancy is most evident at sites with thick surface soils (>100 m), where the 1D models were unable to fully account for subsurface conditions.
For the sites with pronounced discrepancies, deterministic modelling incorporating detailed subsurface characteristics and a higher shear velocity contrast between sediments and bedrock was performed. For sites with low sediment cover (<30 m), modelled FAs aligned closely with experimental results. At sites with medium sediment cover (up to 100 m), modelled FAs were generally lower than the observed values. For deep basin sites (depth > 200 m), deterministic modelling could not reproduce the experimental findings.
These results highlight the limitations of simplified 1D modelling, which primarily accounts for stratigraphic amplification but fails to capture the full complexity of the local seismic response, influenced by path and source effects, as the experimental approach does. Simplified numerical estimates of FAs risk underestimating or misrepresenting seismic site responses, particularly in geologically complex settings such as valleys and intermontane basins. This study underscores the importance of integrating experimental data into seismic hazard assessments to account for the complexity of local seismic responses.
Acunzo, G. et al. 2024. NC92Soil: A computer code for deterministic and stochastic 1D equivalent linear seismic site response analyses. Computers and Geotechnics, 165, p.105857.
Klin, P. et al. 2018. GITANES: A MATLAB package for estimation of site spectral amplification with the generalized inversion technique, Seismol. Res. Lett. 89, no. 1, 182–190.
How to cite: Gallipoli, M. R., Calamita, G., Laurenzano, G., Taverna, P., Klin, P., Totorici, G., Catalano, S., and Barnaba, C.: How reliable are 1D models in reproducing the site seismic amplification functions?: a case study in the Val d’Agri Basin, Italy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10902, https://doi.org/10.5194/egusphere-egu25-10902, 2025.
Campi Flegrei is a nested caldera in Southern Italy well known to the geoscience community for its complex geology and recurrent bradyseismic events. Recently, the interest in the region renewed as a consequence of an ongoing bradyseismic crisis with a particular focus on the associated increment in seismicity. Being one of the most densely populated volcanic areas in the world, with a population of over 500K people, the high social impact that strong seismic events could have makes the monitoring of the area not only of interest for the seismological community but also a priority for the Department of Civil Defence. Consequently, the Department of Civil Defence recently installed several new accelerometric stations in the area, as part of the Italian accelerometric network (RAN), to improve the monitoring operations.
The main goal of this study was to characterize the site response functions at these stations. The analysis has been performed on the recordings from 16 stations for 40 events taking place between 2020 and 2024 with a magnitude between 2.5 and 4.4. A parametric implementation of the generalized inversion technique (GIT) based on a mixed-effects model has been used to model the Fourier amplitude spectra obtained from the recorded waveforms as the contribution of source, path, and site effects, with the inclusion of random effect terms to handle systematic biases related to specific events. The model has been constrained by fixing the frequency-independent site amplification at a reference station, which has been chosen based on a weighted scheme based on geophysical and geomorphological proxies, and then fitted to the data by minimizing the least squares errors. The site response functions (SRFs) have been then obtained by combining the frequency-independent site amplification and the high-frequency correction, obtained during the inversion, with the frequency-dependent site amplification obtained from the analysis of the residuals.
The attenuation parameters obtained from the inversion are consistent with the estimates available in the literature while the magnitudes estimated are in agreement with the ones reported in third-party databases. Furthermore, the results have been validated using a second semi-parametric GIT implementation, in which both source and site effects are treated non-parametrically. The high station-to-station variability of the SRFs at the 16 stations reflects the high geological complexity of the area. The SRFs obtained have been also compared to the corresponding HVSR results: the dominant frequencies are correctly determined using either the GIT approach or the HVSR analysis although the amplitudes from the latter method are generally inaccurate, as well known from the literature. No relevant correlation has been found between the SRFs and the results from (first level) seismic microzonation suggesting that a more detailed analysis is required to provide a correct characterization of the seismic response in the area. The obtained SRFs and seismic spectral model have multiple applications, ranging from Civil Defence purposes to seismic engineering.
How to cite: Fornasari, S. F. and Costa, G.: Site response function evaluation at Campi Flegrei accelerometric stations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11427, https://doi.org/10.5194/egusphere-egu25-11427, 2025.
On November 11, 2019 a very shallow magnitude Mw 4.9 earthquake shook Le Teil (Ardèche, France), some ten kilometres from two nuclear facilities. This earthquake, the strongest in metropolitan France in the last twenty years, occurred on a fault which was not identified as an active fault in the BDFA (Jomard et al., 2017) given its selection criteria, highlighting the importance of studying seismic hazard in low-seismicity areas. This earthquake occurred in a region with many assets, most of which are located in the Rhône valley and therefore subject to significant site effects due to a complex geology. The region has indeed been affected by a major erosion phase during the Messinian salinity crisis ca. 6 My ago, followed by the rapid flooding of the resulting canyon, thereby creating a basin filled with sediments of Pliocene to Quaternary ages embedded in a substratum composed of Secondary to Tertiary formations.
In this study, we present our exploratory work in view to build a seismological model of this region. This will be done through the comparison between observed ground motions and physics-based numerical simulations accounting for uncertainties related to geological layers on the wave path. We want to explore these uncertainties to faithfully replicate the data when modelling the propagation of seismic waves for frequencies between 0.5 and 5 Hz, for scenarios of the Le Teil earthquake and its aftershocks.
We focus particularly on the complexity of the pre-Messinian substratum and its impact on EGM outside the sedimentary basin. We propose a method for building geological interfaces bounding the velocity structure that can easily be parameterized, especially when multiple faults are present, facilitating the investigation of many potential structures.
We were able to produce a first velocity model of the region incorporating faults and a velocity structure with non-planar interfaces, and to confront our numerical simulation of the November 23, 2019 aftershock to field data recorded by several seismic stations. We also identified model parameters subject to uncertainties (shear-wave velocities, layer interfaces, source depth…) and the associated uncertain spaces (approx. 1500-3500 m.s-1, up to 1.5 km variations, approx. 1-2 km depth). Following this work, a comprehensive sensitivity study including basin structure and source parameters will be conducted to understand which physical and structural parameters primarily control the prediction of EGM.
How to cite: Gounelle, A., De Martin, F., Chaljub, E., Lavoué, F., Do Couto, D., Cushing, E. M., and Gélis, C.: Influence of uncertain bedrock seismic velocity structure on numerical simulation of earthquake ground motion (EGM): case study of the Le Teil earthquake (November 11, 2019, France), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9958, https://doi.org/10.5194/egusphere-egu25-9958, 2025.
Site effects arising from complex two- and three-dimensional (2D/3D) site geometries and highly heterogeneous soils cannot be fully captured by traditional one-dimensional (1D) ground response analyses. At geotechnical and sedimentary scales, these effects have been shown to significantly influence earthquake ground motion, leading to amplification or deamplification, duration lengthening, and spatial variability of surface ground motion. In this study, we investigate how complex surface geology and topography affect ground motion characteristics in Beirut, Lebanon. We build a detailed 3D velocity model of the city and its suburbs, incorporating geological, geophysical, and topographical data to reveal large variations in shear-wave velocity structure and seismic bedrock depth. We then conduct 3D numerical simulations of seismic wave propagation up to 5 Hz using spectral-element methods assuming horizontally polarized SH plane waves. We validate our 3D velocity model by comparing simulated and observed site amplifications. Using several ground motion indicators, we identify significant spatial variation of surface ground motion as well as large site amplification and associated ground motion duration lengthening caused by 2D/3D site effects throughout the city. Our findings, based on synthetic ground motions, provide a robust basis for improving seismic damage assessment in Beirut in the event of future earthquakes.
How to cite: Youssef, E., Cornou, C., Youssef Abdel Massih, D., and Al-Bittar, T.: Characteristics of Surface Ground Motion in Beirut, Lebanon, from 3D Seismic Wave Simulation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12809, https://doi.org/10.5194/egusphere-egu25-12809, 2025.
Posters on site: Tue, 29 Apr, 16:15–18:00 | Hall X3
Earthquake induced soil liquefaction first gained importance after the 1964 Alaskan and Niigata Earthquakes. Soil liquefaction is responsible with severe effects due to the decrease in strength and stiffness of the soils underlying the engineering structures following the increase in pore water pressure. Therefore, studies based on the assessment of the liquefaction potentials of the soils have always been significant and in great interest by the researchers. Assessment of the liquefaction potentials of the soils are especially significant for the cities with high population. Fethiye is one of those cities particularly during summers due to high tourist influx (177.569 people in winters, over 1 million people in summers). Fethiye, where is known to be hit by an earthquake with moment magnitude 7.1 in 1957, is estimated to be hit by such an upcoming earthquake in the following years according to the Gutenberg-Richter magnitude-frequency relationship. This paper discusses the liquefaction susceptibilities of the Quaternary deposits within the Fethiye basin calculated according to the simplified procedure. Soil samples from 256 almost evenly distributed boreholes drilled within the microzonation projects within the study area have been used in the calculation of liquefaction susceptibilities of the soils. Calculated factor of safety values have been converted to the liquefaction potential index values to understand the liquefaction hazard. Liquefaction hazard in the region varies from very low to very high (LPI=0 Very Low, 0<LPI≤5 Low, 5<LPI≤15 High, LPI>15 Very High) in the region. According to the analyses, liquefaction potentials of the soils increase towards the coastal margin of the basin where groundwater level gets shallower. Moreover, it has been seen that the clayey soils are not liquefiable according to the Chinese criteria and the liquefiable soils within the study area are mainly sands and silty sands. As it is moved towards the Eastern inland margin, gravel amount increases, groundwater level deepens and liquefaction susceptibilities of the soils decrease. Thus, new urbanization plans must mainly be held in these low susceptible regions, and if it is inevitable not to construct buildings within the liquefiable zone, the essential soil improvement actions must be held to eliminate undesired destructions.
Keywords: Liquefaction, Liquefaction Potential Index, Fethiye, Tourist Attraction, Hazard Mapping.
How to cite: Türe, O. and Celikkollu, S. T.: Assessment of Liquefaction Potentials of the Soils of the World’s one of the Greatest Tourist Attractions for Upcoming High Magnitude Earthquake. Fethiye/Türkiye, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-103, https://doi.org/10.5194/egusphere-egu25-103, 2025.
Despite advancements in physically distributed geo-hydrological models, their small-scale application is often hindered by a lack of quantitative information on geotechnical parameters. Geological and lithological maps, while essential, frequently lack the detailed information needed to enhance their utility in modelling. Addressing this issue, this presentation describes a comprehensive database containing over 2,300 geotechnical parameter records, collected through an extensive review of more than 100 scientific articles and international sources. The parameters include cohesion, friction angle, and porosity, associated to more than 200 different lithotypes. The geotechnical parameters were obtained from laboratory tests, field experiments, or empirical approaches (Monte et al., 2024).
For the Italian context, the collected parameters were associated with the lithological classes defined by Bucci et al. (2022), enabling to present preliminary geotechnical maps. These reclassified maps may provide researchers and stakeholders with a comprehensive dataset useful for slope stability assessments and small-scale land management.
Descriptive statistical analyses and validation through grey literature confirm the reliability and utility of the dataset in enhancing geotechnical characterizations. This database represents a significant advancement for geological and environmental risk assessments at regional and national scales.
Reference
Monte, N., Bucci, F., Mevoli, F. A., Santangelo, M., Reichenbach, P., Di Matteo, L., & Marchesini, I. (2024). A dataset of geotechnical parameters based on international literature to characterise lithotypes in Italy. Scientific Data, 11(1), 1371.
Bucci, F., Santangelo, M., Fongo, L., Alvioli, M., Cardinali, M., Melelli, L., & Marchesini, I. (2022). A new digital lithological map of Italy at the 1: 100 000 scale for geomechanical modelling. Earth System Science Data, 14(9), 4129-4151.
How to cite: Monte, N., Bucci, F., Mevoli, F. A., Santangelo, M., Reichenbach, P., Di Matteo, L., and Marchesini, I.: A Geotechnical Database for Geo-Hydrological Modeling at Regional and National Scales, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3720, https://doi.org/10.5194/egusphere-egu25-3720, 2025.
Predicting the behaviour of existing landslides in mountain regions prone to earthquakes requires a good understanding of the dynamic response of the slopes. Indeed, previous studies, in particular using numerical simulations, have highlighted the role of ground-motion amplifications in the triggering or reactivation of landslides. Unlike seismically active mountain areas where landslides are known to be triggered by earthquakes of magnitude greater than 5, little is known about the potential of repetitive small-magnitude earthquakes to trigger instabilities. This project focuses on an existing slow-moving landslide overhanging the ski resort of Gourette in the French Pyrenees. This landslide, which is approximately 700 m long by 500 m wide at its toe, is active at least since 1990. It is composed of one deep global landslide and several more localized and superficial landslides. The driving force behind this landslide is primarily precipitation. However, if we consider that this region is regularly affected by repetitive small-magnitude earthquakes, the question then arises as to the response of this landslide to seismic shaking. To answer this question, we have started to deploy seismic stations on the slope to measure ground-motion amplifications in the landslide The idea is also to investigate whether the slope ground response varies in time as a consequence of local earthquakes or landslide internal deformations. In parallel, we will also characterize site effects in the landslide area using two methods: the Frequency-Scaled Curvature method and more complex 3D numerical simulations (FLAC3D software). The objective is to characterize site effects within the landslide mass and investigate if combined geological/topographic site effects may develop. In the next months (Interreg POCTEFA SPIRAL project co-financed by EU), additional sensors (GNSS, weather station) will be deployed on the landslide to enable a joint analysis of exogenous factors (precipitation, seismicity) and the landslide's response in terms of surface displacements.
How to cite: Bourdeau, C. and Lombardi, D.: Assessing ground-motion amplifications in a slow-moving landslide (Gourette, French Pyrenees) using seismological data and numerical simulations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19221, https://doi.org/10.5194/egusphere-egu25-19221, 2025.
Seismic site response describes how ground motion changes as seismic waves pass through different types of soil, rock, or structures. This study aims to enhance understanding of local seismic response in areas with cavities, particularly in lava tubes. The seismic response in lava tubes is unique and depends on factors such as the geological characteristics of the tube, its size, and its interaction with surrounding materials. Lava tubes, typically cylindrical or tunnel-shaped, have dimensions - such as length, diameter, and wall thickness - that influence how seismic waves travel through and around them.
The study focuses on the Lamponi grotto, located on the northern side of Mount Etna. The grotto runs in a northeast-southwest direction, extending roughly 600-700 meters. It is divided into two sections: an upstream section, which is about 300-400 meters long and better preserved, and a downstream section, which is shorter and shows signs of roof collapse.
A topographic survey of the lava tube was conducted using a LiDAR system to create a detailed 3D model of both the interior and exterior of the grotto. This high-resolution point cloud data was analyzed to measure the roof thickness, which will be crucial for future numerical modeling and structural analysis.
For seismic site characterization, single-station noise measurements were taken at 50 locations on top of the grotto, with a reference station inside the lava tube. The data were processed using standard spectral ratio methods (comparing outcave vs. incave), vertical-to-horizontal spectral ratios, and Fast Fourier Transform (FFT). Preliminary results indicated strong vertical amplification above the lava tube at frequencies greater than 10 Hz.
How to cite: Panzera, F., Alparone, S., Borzì, A. M., Contraffatto, D., Colica, E., D'Amico, S., Galone, L., Giudice, G., Grechi, G., Larocca, G., Martino, S., Nicotra, S., Gangemi, M. V., and Cannata, A.: Preliminary results on Seismic Site Response Assessment in Presence of a Lava Tube: the Lamponi grotto study case, Etna volcano, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15360, https://doi.org/10.5194/egusphere-egu25-15360, 2025.
In the framework of Italian Seismic Microzonation studies, regional authorities have equipped themselves with simplified procedures, named as “seismic abacuses”, aimed at estimating the amplification of seismic motion. In particular, the purpose of these abacuses is to perform the quantitative characterization of the amplification phenomena expected in lithostratigraphic situations characterized by flat and horizontal layers. These are essentially tables in which a set of values of geophysical parameters considered diagnostic are uniquely associated with expected values of the ground motion amplification in terms of "Amplification Factor" (AF) with respect to a reference motion. The abacuses were defined on the basis of 1D seismic response analyses of real cases considered characteristic and significant of the local lithological, geotechnical and geophysical context of each region. The AF values reported in the regional abacuses correspond to different percentiles of the total number of cases for the period interval considered.The development of the seismic abacuses generally includes 4 steps: geological/geotechnical characterization of the regional territory, parameterization, numerical simulations, statistical analysis and construction of representative abacuses. This work is devoted to describe and summarize the various phases of the procedure done to develop the seismic abacuses of the Piedmont region (Northern Italy).In the first phase, geological, geotechnical and geophysical information collected from regional authority’s repositories were used to define the Geological Domains (GDs), i.e., the areas characterized by similar tectonic and/or depositional history. In the second phase, the seismic, geometric and geotechnical parametrization of the cover terrains for each GD is performed: in particular, the shear-wave velocity (Vs) profiles collected were used to define several models describing the trend of these values as a function of the depth following a power law. As concerns the geotechnical aspects, since the lack of laboratory data, shear modulus reduction and damping ratio curves as a function of shear strain provided for the cover terrains in the Italian territory were considered. The numerical simulations, which represent the third step, were carried out using the NC92Soil software considering an equivalent-linear approach and following the Inverse Random Vibration Theory procedure. In this step, the power-law models previously defined were used to generate via randomization procedure a set of 5000 seismo-stratigraphical profiles for each GD. The last step was devoted to the drawing-up of the abacuses. In this phase, AF values were computed and their population obtained for three period intervals, for each of the GDs and for each of the hazard levels was statistically analyzed and each AF value was classified according to the respective values of geophysical proxy parameters chosen. At the end of the whole procedure, an ensemble of 39 tables was provided to the regional authority.
How to cite: Paolucci, E., Adinolfi, G. M., Comina, C., and Pieruccini, P.: Regional scale geophysical parametrization for the development of simplified method to assess the 1D seismic amplification: the case of Piedmont Region (Northern Italy), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7167, https://doi.org/10.5194/egusphere-egu25-7167, 2025.
Subsoil conditions are known to play a crucial role in modifying earthquake motions at the surface, affecting not only the amplitude but also the duration and frequency characteristics of seismic waves. Seismic microzonation studies, therefore, focus on identifying and mapping areas with homogeneous seismic responses to improve hazard assessment and mitigation efforts.
In this study, we present the preliminary results of the first comprehensive site effects assessment conducted in different parts of Tbilisi, the Capital of Georgia. The analysis includes the characterization of site conditions based on the average shear wave velocity in the upper 30 meters (Vs30), dominant frequencies, and amplification factors. Shallow shear wave velocity (VS30) is a critical parameter in seismic hazard assessment, as it significantly influences the amplification and frequency content of seismic ground motion. While Vs30 in Georgia has traditionally been estimated using refraction techniques, this work incorporates a suite of methodologies, including single-station analysis with borehole data, refraction, Multichannel Analysis of Surface Waves (MASW), and 2D (passive) array measurements. We compare the advantages and limitations of each method, highlighting their effectiveness in different geological and geophysical settings.
Additionally, we generated a resonance frequency distribution map and estimated amplification factors using standard acceleration response spectra as per the EC8 classification guidelines. These findings provide critical insights for improving the seismic resilience of urban infrastructure and serve as a baseline for future seismic hazard studies in the region.
Acknowledgment
This study has been funded by project FR-23-10514 of the SRNSF
How to cite: Tsereteli, N., Dvali, L., Kharanauli, D., Tugushi, N., Kvirtskhalia, T., and Gomidze, L.: Characterizing Subsoil Seismic Behavior: A Case Study of Tbilisi, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11219, https://doi.org/10.5194/egusphere-egu25-11219, 2025.
Seismic hazard assessments in Switzerland rely on the Seismic Hazard Model 2015 developed by the Swiss Seismological Service. The standards for seismic impacts on new constructions or existing structures, as outlined in the official building code for Switzerland, consider seismic zones and local soil conditions. However, no updated hazard assessments currently exist for ETH Zurich or Paul Scherrer Institute (PSI) buildings. The last site-specific studies are now outdated. Existing cantonal soil classification maps for PSI are deficient, relying primarily on geological data, and no soil class map is available for dense urban areas, such as Zurich. Accurate assessments require additional geophysical and seismological data. This pilot project aims to develop detailed soil classification maps for the ETH and PSI areas.
This project’s key steps include analyzing existing geophysical measurements, collecting and interpreting geological and geotechnical data, and conducting new Horizontal-to-Vertical Spectral Ratio (H/V) and array measurements to map soil resonance. Active seismic methods determine site-specific shear-wave velocity profiles and soil damping values. Existing seismic data undergo reinterpretation using advanced techniques, such as high-resolution beamforming and WaveDec, to compute dispersion and ellipticity curves to obtain subsurface velocity profiles with Bayesian inversions.
Subsequently, with the new data, we can estimate local soil amplifications and their variability at investigated sites and classify them into soil classes to produce a soil classification map. Updated seismic hazard studies for two buildings and elastic response spectra accompany an evaluation of the feasibility and effort required for a microzonation study of the ETH and PSI areas.
How to cite: Janusz, P., van Ginkel, J., Bergamo, P., Shynkarenko, A., and Fäh, D.: Developing soil classification maps for earthquake hazard assessment in urban areas, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8729, https://doi.org/10.5194/egusphere-egu25-8729, 2025.
Sedimentary basins play a critical role in ground motion amplification, owing to their complex seismic wave propagation behaviors, which include 2D/3D resonance phenomena and basin edge effects. These characteristics make sedimentary basins key targets for ground motion studies.
A reliable proxy of the seismic response of sedimentary layers is their resonance frequency. This is often assessed through experimental measurements using Horizontal-to-Vertical (H/V) spectral ratio technique, applied to ambient seismic vibrations or earthquake records.
Since resonance frequencies depend on the geometry and mechanical properties of the resonating layer, they can be used as a benchmark for evaluating the accuracy of ground motion models, as simulated ground motion is expected to reproduce amplification at these frequencies.
In this study, we compare basin resonances derived from real and simulated waveforms in two different sedimentary settings in Italy: the narrow Alpine Bolzano basin and the wide intermountain Fucino basin in the Central Apennines. Using stratigraphic data from the literature, we construct 3D models of the basins and perform 3D seismic wave propagation simulations with a spectral-element code. We use both real and synthetic sources to simulate ground motion at the surface and calculate H/V and SSR ratios of the simulated waveforms to be compared with empirical ratios derived from earthquakes and ambient noise.
We analyze the similarities and discrepancies between real and simulated resonances, enabling an evaluation of the goodness of the velocity model used in the simulations. Furthermore, the seismic response of the basins is explored, including an investigation of 1D and 2D dynamic behaviors.
How to cite: Sgattoni, G., Molinari, I., and Di Giulio, G.: Investigating Basin Resonances with 3D Physics-Based Ground Motion simulations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20859, https://doi.org/10.5194/egusphere-egu25-20859, 2025.
3D numerical simulations are widely used to evaluate the impact of topography on ground motion in both homogeneous and heterogeneous media. To ensure consistency among different simulation methods in predicting ground motion amplification and de-amplification on topographic sites, the “BEnchmark of 3D Numerical Simulations on TOpographic Sites” (BENTO) was launched. Partially funded by the Cashima-3 and Sigma-3 research programs, BENTO started in September 2024 and will run until fall 2026, with results to be presented at the ESG 2026 conference in Grenoble, France. The benchmark brings together 20 teams from around the world, including participants from France, Italy, Japan, China, Slovakia, Switzerland, Germany, and the United States. It comprises three main phases.
The first phase is a verification phase, which involves a cross-comparison of high-frequency 3D simulations on simple topographies such as scarps, Gaussian hills/ridges, and triangular hills/ridges, for some of which analytical solutions are also available in the literature. The second phase is an initial validation phase focusing on more complex 3D simulations on a real topographic scarp in Cephalonia, Greece, where existing earthquake recordings are available. In this phase, the goal is to compare synthetic results with real-world measurements and simpler proxies. The final phase is a second validation phase targeting different topographic sites in Cephalonia, for which no prior earthquake measurements exist. New recordings will be collected during this phase, guided by insights from earlier simulations.
BENTO aims to assess the alignment of different numerical methods in evaluating topographic site effects, determine the meshing precision needed to capture small-scale topographic features at high frequencies, define reference rock sites on topographic reliefs, explore the relative influence of topographic parameters on amplification and de-amplification patterns, and address other critical aspects of the physics behind topographic site effects (e.g., focusing and defocusing of waves, wave diffraction).
How to cite: Bou Nassif, A., Maufroy, E., Chaljub, E., Rischette, P., Cornou, C., Bard, P.-Y., El Haber, E., and Hollender, F.: BENTO: A Benchmark on 3D Numerical Simulations for Evaluating the Impact of Topography on Ground Motion, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10022, https://doi.org/10.5194/egusphere-egu25-10022, 2025.
Posters virtual: Wed, 30 Apr, 14:00–15:45 | vPoster spot 3
EGU25-8382 | ECS | Posters virtual | VPS13
1D Site characterization of National Accelerometer stations in Greece based on earthquake recordings and the Diffuse Filed Concept (DFCe)Wed, 30 Apr, 14:00–15:45 (CEST) | vP3.3
This study presents the site characterization of 133 selected stations in the National Accelerometer Network of Greece. All available earthquake recordings for various distances, magnitudes and azimuths around the station are compiled and processed to estimate a stable and reliable average Horizontal -to-Vertical Spectral Ratio (eHVSR). The earthquake records used have magnitude range 4 ≤ M < 6, with focal depth ranging from 0 to 40km and hypocentral distances 12 km ≤ Rhyp ≤ 300 km. Using the Diffuse Filed Concept for earthquakes (DFCe), and incorporating limited a priori geological information, available for the area around the station, the estimated eHVSRs were utilized in an inversion framework to estimate the best misfit velocity profiles down to seismological bedrock (where Vs>=3km/sec). Comparisons of these estimated velocity profiles with existing ones for the selected stations based on other geophysical or/and geotechnical methods, revealed good agreement, encouraging broader application of this methodology for the rest of stations.
In accordance with recommendations from the SERA project, seven key indicators were calculated for each of the 133 stations and are presented as follows: (1) Resonance frequency (f0), (2) Shear wave velocity of the uppermost 30 meters (Vs30), (3) Surface geology description, (4) Current EC8 site class, (5) Depth of the seismological bedrock (H3km/s), (6) Depth of the engineering bedrock (H0.8km/s) and (7) VSZ full profiles where available. Such comprehensive site characterization of accelerometer stations enhances regional and international strong-motion databases (e.g. ESM db) and contributes to exploiting earthquake recordings to their full potential for engineering and seismological applications.
How to cite: Chatzianagnostou, E. and Theodoulidis, N.: 1D Site characterization of National Accelerometer stations in Greece based on earthquake recordings and the Diffuse Filed Concept (DFCe), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8382, https://doi.org/10.5194/egusphere-egu25-8382, 2025.
