The 1 January 2024 Mw7.5 Noto Peninsula earthquake generated a tsunami that spread across the East Sea (Sea of Japan). We investigate the tsunami effect on the coast in regional distances using tsunami-induced seismic wavetrains recorded by borehole broadband seismometers in the Korean Peninsula. The tsunami-induced seismic wavetrains are observed in the seismic stations near the coast. The seismic wavetrains are consistent with the tsunami records in tide gauges. The shared features in waveforms and spectral contents between the tsunami waves and the tsunami-induced seismic signals suggest that the energy origins are the same. The coastal loading of the tsunami induces ground tilting around the coast, producing long-period horizontal wavetrains that are polarized in coastline-perpendicular directions. The long-period tsunami-induced seismic energy deform the medium dynamically. Tsunami-induced deformation decreases with distance from the coast, being effective up to some depths. The amplitudes of tsunami-induced seismic signals are proportional to the amplitudes of tsunami waves. The tsunami-induced dynamic stress change reaches 0.81 kPa on the coast. A large runup height of a tsunami may trigger earthquakes around the coast.

How to cite: Hong, T.-K., Kim, B., Lee, J., Park, S., and Lee, J.: Coastal-medium deformation and seismic hazards induced by the 2024 Noto Peninsula earthquake tsunami, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7608, https://doi.org/10.5194/egusphere-egu25-7608, 2025.

The tsunami earthquake earthquake occurred on 25 of October 2010 in the Indian Ocean about 79 km south-west of Mentawai islands. The tsunami caused severe damage and claimed many victims in some coastal villages. The main purpose of the survey was to measure the inundation and the run-up values as well as to ascertain the possible morphological changes caused by the wave attacks. Attention was particularly focussed on the most affected villages, that is Muntei Barubaru and Malakopak in Mentawai islands. The most severe damage was observed in the Muntei Barubaru. Most places were hit by three significant waves with documented wave height often exceeding 5 m. The maximum runup value (17.00 m) was measured at North Pagai, where also the most impressive erosion phenomena could be found. 

How to cite: Julius, A. M., Priadi, R., Anugrah, S. D., Alfahmi, F., and Kuncoro, ‪. K.: Brief Account of the Post-event survey 2010 Pagai-Mentawai islands tsunami earthquake in Indonesia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1361, https://doi.org/10.5194/egusphere-egu25-1361, 2025.

The extremely shallow location of the seismogenic megathrust in the western Solomons and the existence of significant island land area on the upper plate overlying the seismogenic zone enables us to use corals to obtain vertical motion history closer to the trench and lower plate than anywhere else in the world. In addition, coral paleogeodesy on Porites microatolls acting as long-term vertical positioning station may provide a relative sea level (RSL) change record spanning hundreds of years. Our goal is to develop a centennial record of sea level change and vertical tectonics from multiple Porites microatolls. By isolating the RSL record common to each microatolls, we can then derive a vertical tectonic record by removing the RSL variations from the raw time series recorded by the microatolls.  To achieve that goal, we present recent work combining coral paleogedesy, annual δ13C record and modeling of coral morphology over the last 80 years in the western Solomons. The steps to obtain a long-term record of sea level change and vertical tectonics on samples of a ~80 year old Porites head collected in 2013 after the 2007 Mw 8.1 earthquake. We sampled the coral over 2 to 3 annual bands every ~2 months at various depths and times, performed a stable isotope analysis on each sample, cross-correlated each record and plotted the variation in δ13C versus water depth. Linear regressions show that the variation in accumulated δ13C as a function of water depth relative to the coral’s top water depth is 41 cm/‰ with a R² coefficient of 0.98. We the sampled bimonthly stable isotopes along 80 annual bands. The span of each year is determined from correlating the annual banding and the seasonal cycles in δ13C and δ18O. Applying the linear relationship to the δ13C generates a raw record of relative sea level change. We then use the monthly tide gauge record in Honiara (Guadalcanal) to remove the effects of regional sea level change to the RSL time series obtain from the coral. The result is a record of the vertical tectonic motion of part of the Western Solomon before and after the Mw8.1 2007 earthquake. We analyze the results in terms of the yearly vertical record of the seismic cycle. Current geodetic records at subduction zones constrain at most deformation during one earthquake cycle while multiple earthquake cycles are needed to robustly constrain the physical state of a megathrust.  We hope to be able to extend the coral paleogeodetic record in the Weatern Solomons over several hundred years over multiple seismic cycles.  This would represent a critical data gap that hampers our understanding of subduction physics and our ability to forecast earthquakes.

How to cite: Karaesmen, M. E., Lavier, L., and Taylor, F.: Decadal to Centennial Vertical Paleogeodetic Record of the Seismic Cycle in the Western Solomons from Coral Paleogeodesy and Stable Isotopes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16187, https://doi.org/10.5194/egusphere-egu25-16187, 2025.

We present an overview of the inversions performed with the KF method (Pettenati and Sirovich 2003; Sirovich and Pettenati 2004) on some historical earthquakes in the CPTI15 catalogue data domain. This method is based on a kinematic function (KF) that is controlled during the inversion by the Genetic Algorithm with Niching's Variant (NGA) algorithm (Gentile et al. 2004).

Since we are dealing with historical earthquakes, a distinction is first made between instrumental and pre-instrumental earthquakes. For the former between 1900 and 2009 a quantitative assessment is made, for the latter only qualitative assessments can be made. We present statistics to evaluate the magnitude and epicentral coordinates obtained from KF with instrumental data or the parameters of the CPTI15 catalogue. To evaluate the fault plane solutions, we instead used the disorientation angles with the instrumental focal mechanisms (Sirovich et al. 2013). In the case of pre-instrumental earthquakes, the assessments vary from case to case. From the comparison of the results obtained with techniques based on the conversion of strong motion data into intensity, statistical analysis or comparison with the seismotectonic of the area could be made.

References

Gentile, F., F., Pettenati and Sirovich, L.; 2004. Validation of the Automatic Nonlinear Source Inversion of the U. S. Geological Survey Intensities of the Whittier Narrows, 1987 Earthquake. Bull. Seism. Soc. Am., vol.94, No.5, 1737-1747, October 2004, https://doi.org/10.1785/012003157.

Pettenati, F., and Sirovich, L.; 2003. Test of Source-Parameter Inversion of the USGS Intensities of the Whittier Narrows, 1987 earthquake. Bull. Seism. Soc. Am, vol.93, No.1, 47-60, February 2003, https://doi.org/10.1785/0120010113.

Sirovich, L. and. Pettenati, F; 2004. Source Inversion of Intensity patterns of Earthquakes; a Destructive Shock in 1936 in northeast Italy. Journal of Geophysical Research, vol. 109, B10309, 2004, 1-16, https://doi.org/10.1029/2003JB002919.

How to cite: Pettenati, F.: The KF-NGA technique for the inversion of macroseismic data. Summary of the solutions obtained from the CPTI15 catalogue data., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16200, https://doi.org/10.5194/egusphere-egu25-16200, 2025.

The assessment of ground shaking at high spatial resolution after a recent or future earthquake is crucial for rapid impact assessment and risk management. This is even more important in the urban context, where small-scale differences can have a significant effect on the impact of the earthquake on people and property. Classical seismological networks, however, are usually too sparse to capture the variability of ground shaking at high spatial resolution. In this paper, we show how a multivariate spatial statistical model can be used to improve ShakeMaps by integrating station data (e.g. peak ground accelerations), data from citizen science initiatives (e.g. smartphone accelerations and felt reports), and macroseismic data. The statistical model accounts for the heterogeneity of the data sources in terms of spatial density, measurement uncertainty and bias. The model achieves data fusion without the need for calibration relationships and co-located information, and provides the ShakeMap uncertainty in a natural way.

Our approach is applied to events measured by a seismological network and by the smartphones of the Earthquake Network citizen science initiative, and for which felt reports from the LastQuake app of the European-Mediterranean Seismological Centre and macroseismic information by the Italian National Institute of Geophysics and Volcanology are available.

How to cite: Finazzi, F., Bossu, R., Cotton, F., Filote Pandelea, S. M., and Vannucci, G.: Enhancing ShakeMaps using crowdsourced smartphone data and macroseismic information through spatial statistical modelling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11406, https://doi.org/10.5194/egusphere-egu25-11406, 2025.

Predicting large earthquakes remains a complex and critical challenge in seismology. This study investigates distinctive seismic precursors by analyzing unique waveform patterns in foreshock sequences. Using the 2011 Mw9.1 Tohoku earthquake as a case study, preceded by a Mw7.3 foreshock, we identified an anomalous sawtooth pattern in the ground velocity envelope following the foreshock. Unlike typical post-earthquake recordings, this pattern is interpreted as evidence of the locked state of the mainshock fault, which suppresses the foreshock’s ability to trigger aftershocks.
To quantify these waveform anomalies, we developed the index Q based on the first 45 minutes of waveform recordings. Applying this method to 75 Mw6+ earthquakes recorded globally since 2010, our approach correctly identified 10 out of 11 foreshock sequences that preceded larger earthquakes within 10 days. Only 7 out of 64 remaining earthquakes were misclassified, highlighting the robustness of the method.
Our findings suggest that these sawtooth patterns are reliable indicators of impending large earthquakes, offering a novel tool for seismic forecasting. By integrating this method with other geodetic and seismological datasets, we aim to enhance hazard assessment and mitigation strategies, contributing to improved preparedness for future seismic events.

References

¹Lippiello, E., Petrillo, G., Godano, C., Tramelli, A., Papadimitriou, E., & Karakostas, V. (2019). Forecasting of the first hour aftershocks by means of the perceived magnitude. Nature communications, 10(1), 2953.

How to cite: Petrillo, G., Lippiello, E., Dal Zilio, L., and Godano, C.: Quantifying Foreshock Anomalies: Insights from Envelope Waveforms, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14111, https://doi.org/10.5194/egusphere-egu25-14111, 2025.

Eastern Part of the Czech Republic in the Outer Western Carpathians (OWC), particularly the Javorníky Mts. range along the Czech-Slovakian border, has been traditionally considered a geologically stable region with documented low contemporary seismic activity. However, recent geomorphological analyses and field investigations reveal compelling evidence of prehistoric large-scale and highly mobile mass movements, potentially triggered by paleo-earthquakes. This study integrates high-resolution LiDAR mapping, field investigations and trenching, geophysical surveys, radiometric dating, and numerical modeling to reconstruct the paleo-seismic characteristic of the region. 
We identified those paleo-landslide features using high-resolution LiDAR data and assumed their relationship to past seismic activity by their close vicinity to a Holocene polyphase surface rupture of the Lidečko Fault. LiDAR mapping combined with the Electrical Resistivity Tomography (ERT) analyses provide valuable insights into the structural geology, lithology, failure mechanisms of paleo-landslides. Trenching and dating techniques, including radiocarbon and optically stimulated luminescence (OSL), help establish the timing of these events and their possible seismic triggers. Structural analysis of the Lidečko revealed the active strike-slip and oblique reverse kinematics with surface ruptures and liquefaction features, supporting the hypothesis of the landslides´ earthquake-induced origin.
Distinct three generations of landslides were identified as half-ellipsoidal depleted source zones about 400 m long, 200 wide and about 25 m deep with remnants of their accumulations at the toe and in the valley floor and different state of subsequent reworking by shallow slope processes. The fluidized mass was displaced for up to 1 km, of which up to 600 meters comprised totally flat riverbed. Radiometric dating of associated landslide-dam deposits revealed the landslides´ ages about 91 ka, 45 ka and 1.8 ka ago.
To accurately assess their potential coseismic origin, synthetic seismic acceleration data derived from waveform records in the OWC region is integrated into both Newmark Displacement Analysis (NDA) with the Velocity-Dependent Friction Law (VDFL) and the distinct element numerical modeling. This combined approach improves the simulation of rock mass and landslide dynamics under seismic loading conditions and ensures a more precise analysis of earthquake-induced slope processes. Specifically, PFC3D numerical modeling is employed to reconstruct the paleo-topography and simulate the long run-out behavior of paleo-landslides under various earthquake scenarios. These simulations provide deeper insights into the triggering mechanisms and movement patterns of such landslides.
The estimated magnitudes of past earthquakes challenge assumptions about the OWC's seismic stability and suggest significant unrecorded events. This study improves understanding of earthquake-induced landslides in stable regions and offers a framework for assessing long-term seismic hazards. The methods used can be applied to other areas with uncertain seismic histories, helping to better understand the connection between tectonics and landscape evolution.
The research was funded by the Grant Agency of the Czech Republic (GC22-24206J) and Taiwanese National Technological and Science Council (MOST/NTSC 111-2923-M-008-006-MY3).

How to cite: Nguyễn, T.-T., Baroň, I., Dong, J.-J., Melichar, R., Hartvich, F., Klimeš, J., Černý, J., Šutjak, M., Kociánová, L., Dušek, V., Rowberry, M., Braucher, R., Goslar, T., Tseng, C.-H., Chen, Y.-C., Lin, C.-H., and Gao, J.-Q.: Revealing Hidden Seismic Histories: Prehistoric Landslides as Indicators of Paleo-Earthquakes in the Outer Western Carpathians, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15884, https://doi.org/10.5194/egusphere-egu25-15884, 2025.

We know more about earthquake processes, vulnerability modelling and characterization of the built environment than ever before. Yet, earthquake losses and casualties continue to increase, even in countries where modern seismic design regulations have been introduced decades ago. In this study we investigate the drivers of earthquake damage and losses using the global seismic hazard and risk model developed by the Global Earthquake Model (GEM) Foundation and its partners, as well as data from fatal earthquakes since 1950. We isolate specific parameters that can influence the severity of the ground shaking, the vulnerability of the building stock, and the spatial distribution of the population. These include the prevalence of soft soils, the average seismic hazard in each country, the likelihood of experiencing extreme ground shaking, the occurrence of earthquake-triggered hazards (i.e., liquefaction, landslides and tsunamis), the time of the event, the proximity of megacities to active faults, the percentage of specific types of construction, and some socio-economic factors. We compare these underlying parameters and the estimated or observed seismic risk between different countries and identify specific patterns that systematically exacerbate the overall impact. We observe that high economic losses are frequent in countries with well-established seismic regulations not only due to the high replacement/repair costs, but also due to the high prevalence of commercial and industrial facilities and complex infrastructure. On the other hand, high fatality risk is frequent in countries whose building stock is comprised of non-engineered buildings with heavy roofs and floors. Another relevant observation is that although ground shaking is overwhelmingly the main cause of damages and losses, under specific geological and demographic conditions, the impact of tsunamis, landslides and liquefaction phenomena can be devastating. Lessons drawn from these observations and patterns can be useful to understand how the impact of earthquakes can be better assessed, reduced, and managed.

How to cite: Silva, V., Aljawhari, K., Baiguera, M., Calderón, A., Caruso, M., Costa, C., González González, D., Nafeh, A. M. B., Rao, A., Yepes, C., and Karimzadeh, Z.: Drivers of Earthquake Damage and Losses: a Global Perspective on Where and Why Seismic Risk is High, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21102, https://doi.org/10.5194/egusphere-egu25-21102, 2025.