Seismic Hazard Assessment Research Articles

A Seismic Landslide Hazard Assessment in Small Areas Based on Multilevel Physical and Mechanical Parameters: A Case Study of the Upper Yangzi River

Many landslides triggered by earthquakes have caused a countless loss of life and property, therefore, it is very important to predict landslide hazards accurately. In this work, regional seismic landslide data were obtained via a field survey, remote sensing interpretation, and data collection, and a multilevel physical and mechanical parameter system for seismic landslide hazard assessment was established; this system included a landslide inventory, loose accumulation layers, and geological units, enabling higher accuracy in the data. The Newmark displacement model with a modified correlation coefficient was used to assess the regional seismic landslide hazard in four scenarios (a = 0.1, 0.2, 0.3, 0.4) to study the influence of the landslide hazard at different peak ground accelerations. Moreover, the information value model was used to modify the calculated results to improve their accuracy in the assessment. By assessing the potential seismic landslide hazard in Shimian County in the upper reaches of the Yangtze River, the regional landslide distribution and pattern at different peak ground accelerations were obtained. The results show that with decreasing parameter accuracy in the system, the importance of the landslide inventory increases. When the peak ground acceleration is a = 0.3, which can be defined as a high hazard grade, in which the landslide area demonstrates a large-scale sharp increase, a devastating hazard threshold is reached. As the peak ground acceleration increases, the factor controlling landslides transforms from the landslide inventory to the slope, which reflects the reasonableness of the parameters in the system. The input parameters were regarded as important factors for efficiently increasing the accuracy of the results of the Newmark displacement model in the discussion.

Seismic and GNSS strain-based probabilistic seismic hazard evaluation for northern Chile using DAS Magnitude Scale

BackgroundProbabilistic Seismic Hazard Assessment (PSHA) is a leading methodology for determining key ground motion parameters such as Peak Ground Acceleration (PGA) and spectral acceleration (SA), essential for structural design. This approach uses extensive earthquake data, typically spanning over a century, leveraging frequency and magnitude statistics. However, long-term ground shaking probabilities may not always be accurately captured by traditional data-driven methods. To address these limitations, this study develops a PSHA map for Northern Chile using both seismic and GNSS (Global Navigation Satellite System) data. A curated homogeneous earthquake catalog, based on the advanced seismic moment magnitude scale Mwg(Das Magnitude Scale), replaces the traditional Mw scale to ensure superior accuracy, particularly for intermediate and smaller earthquakes.ResultsUsing the earthquake catalog, seismicity parameters ‘a’ and ‘b’ from the Gutenberg-Richter relationship were derived. Seismogenic modeling and Ground Motion Models (GMMs) were applied to estimate ground motion probabilities for a 475-year return period. Additionally, a PSHA map was constructed using GNSS strain rates, translating velocity-derived strain rates into seismic moment rates and ground shaking probabilities for seismic source zones. Comparative analyses revealed higher PGA values from GNSS strain data compared to seismic catalog data. GNSS strain data proved invaluable for refining seismic segmentation in Northern Chile, enhancing the precision of PSHA calculations.ConclusionsA PSHA map for Northern Chile, synthesizing seismic catalog data and GNSS strain rates using a Logic Tree-based algorithm, has been developed for a 475-year return period. This map provides a critical tool for generating seismic hazard assessments aligned with building codes and emergency planning protocols. By integrating GNSS strain rates and seismic data, this study advances the reliability and accuracy of long-term ground shaking predictions.

Understanding earthquake potential for future hazard mitigation

This study re-examines a broad region of the Sumatran subduction zone and off-coast southern West Java, building on findings of relative quiescence and utilizing the modified probability gain (mG) concept. By comparing pre- and post-quiescence seismicity, we identify potential earthquake sources and assess associated tsunami hazards. We propose a novel combined model integrating normalized seismicity smoothing, geodetic moment rate, and mG to characterize earthquake likelihood better. This model, coupled with a robust seismicity rate model, enables a spatiotemporal earthquake potential hierarchy for refined seismic hazard assessment. Our results confirm prior quiescence findings in specific zones and identify novel potential source regions for significant future earthquakes. We estimate tsunami height, emphasizing the importance of multiple source areas and static stress loading. By examining pre- and post-event expectations, we aim to improve understanding of major earthquakes in the Sumatran Subduction Zone and inform disaster mitigation strategies. This study provides crucial insights for enhanced regional earthquake and tsunami preparedness.

Preliminary study site characterization using HVSR microtremor in West Bandung Basin

Site characteristic become crucial factor in seismic hazard assessment correspond to the site response of earthquake motions. This study investigates site characterization in the western part of the Bandung Basin using the Horizontal-to-Vertical Spectral Ratio (HVSR) method. HVSR analysis was applied to the Rayleigh wave microtremor data that was conducted at observation sites i.e: Baros, Cibeber, Batujajar, and Giriasih. The analysis results revealed some soil parameters i.e: dominant period (Td) values ranging from 0.23 to 0.43 seconds, S-wave velocity structure down to a depth of 30 (Vs30) in a range of 173.25 m/s in Cibeber to the highest was 281.76 m/s in Baros. The result of Vs30 analysis were used to classify local site which is Baros site can be classified into the stiff soil (SD) category, Cibeber and Batujajar belong to the soft soil (SC) category, and Giriasih is classified as very soft soil (SE). The findings of this study provide valuable information for seismic hazard assessment, seismic site classification, and earthquake-resistant structural design in the western part of the Bandung Basin.

Mapping near-surface S-wave attenuation in the onshore southeastern flank of the Red Sea Rifting system in Saudi Arabia

This study aims to quantify the site attenuation parameter, kappa (κ), in the southeastern flank of the Red Sea rifting system. To determine κ, a least-squares best-fit method was applied to three-component seismograms, allowing for the modelling of the Fourier amplitude spectra of S-waves. The dataset consisted of 53 earthquakes, ranging in local magnitudes from 3.0 to 4.8 ML. The estimates of κ for 17 sites in the southeastern flank of the Red Sea region revealed average values ranging from 0.026 ± 0.01s to 0.053 ± 0.01s. A statistical analysis of κ dependence on epicentral distance, near-surface geology, and earthquake magnitude demonstrated the dependence of κ on distance and surface geology rather than earthquake magnitudes. The spatial distribution of the parameter κ, which includes both path and site effects, shows higher values at soft rock sites in the eastern region than hard rock sites in the western area. Owing to surface geological conditions, the site-dependent parameter κo exhibited average values of 0.002 ± 0.003s and 0.024 ± 0.002s for the hard and soft rocks, respectively. The results may be used to improve seismic hazard assessments and earthquake ground motion simulations.

Sensitivity Analysis on the Impact of Input Parameters on Seismic Hazard Results: A Case Study of Central America

We present a sensitivity analysis on the impact of input parameters and methods used on the results of a probabilistic seismic hazard assessment (PSHA). The accurate estimation of the parameters in recurrence models (declustering and fitting methods), along with the selection of scaling relationships for determining maximum magnitude and the selection of ground motion models (GMMs), enhance control over epistemic uncertainties when constructing the logic tree, minimizing final calculation errors and producing credible results for the study region. This study focuses on Central America, utilizing recent data from seismic, geological, and geophysical studies to improve uncertainty analyses through classic statistical methods. The results demonstrate that proper fitting of the recurrence model can stabilize acceleration variations regardless of the declustering method or b-value fitting method used. Regarding scaling relationships, their low impact on the final results is noted, provided the models are tailored to the tectonic regime under study. Finally, it is shown that the GMM contributes the most variability to seismic hazard results; therefore, their selection should be conditioned on calibration with observed data through residual analysis where region-specific models are not available.

Seismic hazard assessment of Agartala agglomeration based on 1D nonlinear ground response analysis and empirically derived liquefaction susceptibility

Seismic hazard assessment of Agartala agglomeration based on 1D nonlinear ground response analysis and empirically derived liquefaction susceptibility

Combining Two Distinct Methods to Resolve Spatial Variation in Attenuation and Earthquake Source Parameters

ABSTRACT Stress drop is a fundamental parameter in ground-motion modeling and seismic hazard assessment, but spectral estimates are subject to considerable uncertainties. A variety of factors cause different methods to yield different results, including the complexity of the seismic source, the assumptions inherent in the models used, the limited range of frequencies available, and the inherent difficulty in removing the propagation effects along the wave path. A primary challenge is determining whether the observed variations in spectral stress-drop estimates represent characteristics of the seismic source or the propagation path. We compare the performance of two methods applied to the 2019 Ridgecrest, California, earthquake sequence, each of which addresses the trade-offs between propagation and source in different ways. The first method, referred to as the spectral-fitting approach, operates on the hypothesis that the path effects remain constant across the spatial and temporal range of the sources under investigation. This approach assumes a level of uniformity in the propagation effects that simplifies the analysis. The second method, referred to as the spectral ratio approach, is based on the hypothesis that a small, collocated event will experience identical propagation effects to the earthquake of interest, potentially accounting for smaller scale variation in propagation effects. Our comparison reveals that the choice of method is not only influenced by the specifics of the data and the seismic events but also significantly constrained by the geological heterogeneity and consequent spatial variability of site and propagation effects in the study area. If an approach involves assuming a homogeneous attenuation structure, any spatial variation in attenuation structure will lead to this variation being incorrectly mapped into apparent source stress-drop variations. Understanding the local geology and structural heterogeneity, combined with using methods with contrasting underlying assumptions are good approaches to improving the reliability of estimated spectral stress drops.

Automatic classification of near‐fault pulse‐like ground motions

AbstractThis study presents an automated, quantitative classification method for near‐fault pulse‐like ground motions, distinguishing between forward‐directivity and fling‐step (FS) motions. The method introduces two novel parameters—the pulse velocity ratio and pulse area ratio—which transform the classification standard from a qualitative to a quantitative framework. Combined with an enhanced pulse extraction technique that captures permanent displacement characteristics, these parameters significantly improve classification efficiency and repeatability. This automated approach overcomes the limitations of manual classification, providing reproducible results. The identified FS ground motions can be applied to the dynamic analysis of cross‐fault structures, enhancing the reliability of seismic hazard assessments.

Correlations between spectrum-based and other ground-motion intensity measures considering various damping ratios

Spectral acceleration at a given period, SA( T), is usually combined with other intensity measures (IMs) for vector-valued ground-motion selection and seismic hazard assessment. The correlations between SA( T) and other IMs have been extensively studied, based on the SA-related IM pairs with a damping ratio ( ξ) of 5%. Yet, ξ varies notably with various types of structures. This article thus investigates the correlations of SA( T, ξ) with 10 commonly used non-SA IMs (e.g. Arias intensity), and the correlations of damping-specific acceleration spectrum, spectrum, and displacement spectrum intensities, namely ASI( ξ), SI( ξ), and DSI( ξ), with the other IMs. Comprehensive correlation analyses are conducted to derive the correlations for the IM pairs considered based on the NGA-West2 database and compatible ground-motion models. The results indicate that increasing ξ generally yields stronger correlations, and the difference between the ξ-specific and 5%-damped correlation coefficients could be larger than 0.2. The neural network and polynomial regressions are subsequently used to develop parametric models for estimating the correlations of SA( T, ξ)-containing pairs and the other IM pairs, respectively. All the models developed exhibit good performance in terms of predictive accuracy. The application of the proposed models is demonstrated within the generalized conditional IM approach. The models proposed could be useful for ground-motion selection and seismic demand or risk assessment for structures with various ξ values.

Database of seismological observations in the Severomuysky region of the Baikal rift during the operation of the local network of stations

The Severomuysky region should be considered as one of the key areas of the northeastern flank of the Baikal rift zone. The most important infrastructure facilities of the Baikal-Amur Mainline, in particular the Severomuysky tunnel, require an objective assessment of the seismic hazard of this territory. The work on converting a unique set of seismological data obtained during the period of operation of the analog local network of seismic stations (1978-1993) into digital format was carried out at the BB GS RAS in order to ensure the safety of all primary seismological observation materials and comprehensive analysis. This information was presented in printed form only. A database has been developed. It provides a relational approach to storing and managing large volumes of data. The database contains complete information on 15,832 earthquakes with KP=4–13 (station information, catalogues, bulletins, etc.). A client application has been created for convenient work with the database. The article illustrates examples of working with a database when solving typical seismological problems. It is obvious that extensive seismological information presented in digital form is of great importance for assessment of seismic hazard of the study under region.

Identification of lineaments in the Laptev Sea region by geomorphometric methods: application to seismic hazard assessment

This article examines aspects of the application of geomorphometric methods to the identification of regional-scale lineaments using a digital relief model and a gravity field model in marine areas using the Laptev Sea as an example. The results of lineament analysis showed their applicability for further use in developing a model of earthquake source zones and seismic hazard assessment. The study showed the effectiveness of methods of shadow analysis and identification of keel forms by calculating the curvature of the relief for identifying large seismic lineaments, provided that the results of geomorphometric analysis are used together with data on the distribution of earthquake epicenters. The presented approach to identifying seismic lineaments can be very promising for the development of a lineament-domain-focal model of zones of possible earthquake sources in the vast shelf zones of Russia, for which there is no necessary volume of geological, geophysical and paleoseismological data.

Seismic hazard assessment in the Podhale region, Poland—zone and smoothed seismicity approach

AbstractPoland is characterised by weak natural seismicity. However, the last analysis of the natural seismic hazard in the country was carried out 24 years ago. Therefore, a significant fraction of the recorded seismicity is not included in the hazard estimates currently used, either because recent observations are not taken into account or because of improved seismic network capabilities. Furthermore, Podhale, in the Tatra Mountains, is the only region with recorded permanent natural seismicity. This study aims to create new seismic hazard maps of the Podhale region from a newly compiled database containing information on historical events and two complete instrumental catalogues (regional and local), each at a different level of completeness. The local catalogue was recorded over the last few years. Two seismic hazard assessment techniques were applied, namely the conventional (zone-based) (Cornell in Bull Seismol Soc Am 58(5): 1583–1606, 1968) and the smoothed seismicity model, based on the spatial distribution of seismicity. The earthquake recurrence parameters were estimated using the methodology developed by Kijko et al. (Bull Seismol Soc Am 106: 1210–1222, 2016). The new seismic hazard model incorporates several improvements, such as a comprehensive logic tree and a new set of ground motion models. The new maps provide a more detailed assessment of the seismic hazards of the investigated area. Moreover, they predict higher PGA than previous seismic hazard maps covering Podhale, like global European Seismic Hazard Maps 2013 and 2020.

Earthquake Fault Rupture Modeling and Ground-Motion Simulations for the Southwest Iceland Transform Zone Using CyberShake

ABSTRACT CyberShake is a high-performance computing workflow for kinematic fault-rupture and earthquake ground-motion simulation developed by the Statewide California Earthquake Center to facilitate physics-based probabilistic seismic hazard assessment (PSHA). CyberShake exploits seismic reciprocity for wave propagation by computing strain green tensors along fault planes, which in turn are convolved with rupture models to generate surface seismograms. Combined with a faultwide hypocentral variation of each simulated rupture, this procedure allows for generating ground-motion synthetics that account for realistic source variability. This study validates the platform’s kinematic modeling of physics-based seismic wave propagation simulations in Southwest Iceland as the first step toward migrating CyberShake from its original study region in California. Specifically, we have implemented CyberShake workflows to model 2103 fault ruptures and simulate the corresponding two horizontal components of ground-motion velocity on a 5 km grid of 625 stations in Southwest Iceland. A 500-yr-long earthquake rupture forecast consisting of 223 hypothetical finite-fault sources of Mw 5–7 was generated using a physics-based model of the bookshelf fault system of the Southwest Iceland transform zone. For each station, every reciprocal simulation uses 0–1 Hz Gaussian point sources polarized along two horizontal grid directions. Comparison of the results in the form of rotation-invariant synthetic pseudoacceleration spectral response values at 3, 4, and 5 s periods are in good agreement with the Icelandic strong motion data set and a suite of empirical Bayesian ground-motion prediction equations (GMPEs). The vast majority of the physics-based simulations fall within one standard deviation of the mean GMPE predictions, previously estimated for the area. At large magnitudes for which no data exist in Iceland, the synthetic data set may play an important role in constraining GMPEs for future applications. Our results comprise the first step toward comprehensive and physics-based PSHA for Southwest Iceland.

Reanalysis of historical earthquakes to improve seismic hazard assessment: Case study of the 1880 Zagreb (Croatia) earthquake

Reanalysis of historical earthquakes to improve seismic hazard assessment: Case study of the 1880 Zagreb (Croatia) earthquake

Sparse fault representation based on moment tensor interpolation

Accurate representation of large earthquake sources is required for understanding rupture dynamics and improving seismic hazard assessments. While capable of capturing complex spatio-temporal slip scenarios, traditional finite-fault models often suffer from over-parameterization, require strong regularization, and pose significant computational challenges, especially in rapid-response scenarios. Conversely, multiple point source (MPS) models reduce the rupture as a sequence of point sources but are inadequate to simulate short-period wavefield and static displacement. We introduce a hybrid source representation that leverages moment tensor interpolation to bridge the gap between these models. By treating moment tensors as "key" centroids of a tensor field, we construct geometrically coherent slip models that retain the spatial complexity of finite-fault models while maintaining MPS's computational efficiency and simplicity. Our method extends existing 2D tensor-field reconstruction techniques to moment tensors, allowing source-type-preserving interpolation and enabling sparse model approximation and source upscaling for numerical simulations. We demonstrate how our approach can benefit both the inverse and forward problems on the January 2024 Noto earthquake, computing a sparse approximation of the USGS NEIC source model with fewer than ten key tensors and computing full wavefield and static deformation from upscaled source distributions in a realistic 3D regional tomographic model using spectral-elements method.

The Limits of Applicability of the Gutenberg–Richter Law in the Problems of Seismic Hazard and Risk Assessment

The Gutenberg–Richter law establishes a log-linear relationship between the number of earthquakes that have occurred within some spatiotemporal volume and their magnitude. This similarity property presumably reflects fractal structure of the fault system in which earthquake sources are formed. The Gutenberg–Richter law plays a key role in the problems of seismic hazard and risk assessment. Using the Gutenberg–Richter relationship, we can estimate the average recurrence period of strong earthquakes from the recurrence rate of weaker earthquakes. Since the strongest earthquakes occur infrequently, with intervals of a few hundred years or more, it is not possible to directly assess their recurrence. From indirect geologic and paleoseismic estimates it often seems that strong earthquakes on individual faults occur more frequently than expected in accordance with the Gutenberg–Richter law. Such estimates underlie the hypothesis of the so called characteristic earthquakes. This hypothesis is in many cases additionally supported by the form of the magnitude–frequency distributions for individual faults, constructed from the data of modern earthquake catalogs. At the same time, an important factor affecting the form of the magnitude–frequency distribution is the choice of the spatial domain in which the distribution is constructed. This paper investigates the influence of this factor and determines the conditions under which the Gutenberg–Richter law is applicable for estimating the recurrence of strong earthquakes.

On the Use of Medium-Term Forecast Data for the Baikal Rift Zone in Seismic-Hazard Assessments

The article presents the general results of medium- and long-term forecasting of earthquakes with K ≥ 13 (M ≥ 5.0) in the Baikal rift zone. These results have recently been obtained through the joint use of the geoinformation system for predicting the preshock stage of earthquake preparation and its associated two-stage phenomenological model. This model was created based on the analysis of seismological data on the preparation of the most dangerous earthquakes that occurred in the Baikal rift zone. It is consistent with the results obtained in studies of seismic regimes of ice shock preparation on the Baikal ice cover and in conducting full-scale experiments on fault sections with the aim of clarifying physical and mechanical conditions for the emergence of the sources of seismic-induced oscillations.The paper provides an example of practical use of results obtained for earthquake forecasting, as well as the ways of refining seismic hazard assessments relative to the infrastructure in the city of Angarsk 100 km away from the seismically hazardous Main Sayan Fault (MSF), whose zone reveals a “locked” segment with a seismic gap during the seismic regime analysis. In accordance with its linear dimensioning which represents a length of 60 km, two L/M equations served as a basis for potential energy calculations whose maximum values correspond to Mmax 7.1 and 7.8. It is shown that the use of the obtained earthquake-forecast results assists in refining the level of seismic hazard for the nearest time intervals of expected earthquakes with different Mmax values. Consideration is being given to the example of assessing the current seismic hazard using a medium-term forecast for the infrastructure of the city of Angarsk for the probability of seismic shaking from the southeastern section of the MSF zone for the next 10 and 50 years. The comparison with the OSR-16 map showed that the calculations carried out indicate a relatively lower level of seismic hazard for the city of Angarsk for 10- and 50-year expectation periods.

Basement Neo-Tectonics of Western Himalayas from Seismic and Gravity Data Perspective

An earthquake of magnitude (Mw) 4.3 occurring on April 6, 2024 near Sargodha (Mianwali NW Punjab, Pakistan) has been analyzed through waveform inversion to understand the subsurface geological structure. This shallow-depth (19 km) event represents a strike-slip faulting with a dextral sense of movement. Gravity data of the epicentral area depicts distinct anomalies representing two separate blocks showing an off-set in the same direction as determined by the seismic inversion validating modeling results. In our opinion, these structures represent second-order tectonics, potentially emerging as a response to the hindrance caused by the Sargodha High to southward movement of the Himalayan deformation front. Alternatively, R-shears associated with the western boundary of the Indian plate could provide another explanation for such strike-slip mechanism events. Crustal shortening along the deformation front is being accommodated through aseismic slip along a viscous décollement in the Salt Range and seismic slip within the brittle basement rocks of the Sargodha region as represented by the analyzed seismic event. This dual process plays a key role in shaping the tectonic features in study area. Detailed studies of small to moderate seismic events can help in delineating the subsurface seismogenic structures for development of better seismo-tectonic model for realistic seismic hazard assessment in the region.

Do slip-weakening laws shapes influence rupture dynamics?

To model rupture dynamics, a friction law must be assumed. Commonly used constitutive laws include slip-weakening laws which are characterized by a drop from static to dynamic frictional stress over a critical slip distance. Within this framework, the prevailing understanding asserts that the frictional behavior is solely controlled by the fracture energy — the area beneath the frictional stress versus the cumulative slip curve. In particular, it is claimed that the curve’s shape itself has no influence on the system’s response. Here we perform fully dynamic rupture simulations to challenge prevailing beliefs by demonstrating that the constitutive law shape exerts an intimate control over rupture dynamics. These results are confirmed using two independent numerical schemes (spectral boundary integral and finite element methods). For a consistent fracture energy but varying constitutive weakening law shapes, the slip velocity profile is different: each abrupt slope transition leads to the localization of a distinct velocity peak. For example, in the case of a bilinear slip-weakening law featuring two different slopes, the rupture exhibits two distinct velocity peaks. This phenomenon arises from the transition between a constant weakening rate to another. We show that ruptures with the same fracture energy but different constitutive law shapes may respond differently to stress barriers, especially when cumulative slip is below the critical slip Dc. In these cases, variations in effective fracture energy across different laws lead to differing outcomes: under one law, a rupture may propagate past a barrier, while under another, it may arrest. These findings underscore the critical role of constitutive law shape on rupture dynamics, influencing the response to small-scale asperities and heterogeneities and to larger-scale barriers, and highlighting the importance of both fracture energy and weakening mechanisms for seismic hazard assessment.