Hamlet: An Application for Seismic Hazard Model Evaluation and Testing

The Earthquake Model of Middle East (EMME) Project aimed to develop regional scale seismic hazard and risk models uniformly throughout a region extending from the Eastern Mediterranean in the west to the Himalayas in the east and from the Gulf of Oman in the south to the Greater Caucasus in the North; a region which has been continuously devastated by large earthquakes throughout the history. The 2014 Seismic Hazard Model of Middle East (EMME-SHM14) was developed with the contribution of several institutions from ten countries. The present paper summarizes the efforts towards building a homogeneous seismic hazard model of the region and highlights some of the main results of this model. An important aim of the project was to transparently communicate the data and methods used and to obtain reproducible results. By doing so, the use of the model and results will be accessible by a wide community, further support the mitigation of seismic risks in the region and facilitate future improvements to the seismic hazard model. To this end all data, results and methods used are made available through the web-portal of the European Facilities for Earthquake Hazard and Risk ( www.efehr.org ).

Comparison between outcomes of the 2014 Earthquake Hazard Model of the Middle East (EMME14) and national seismic design codes: The case of Iran

Abstract. Seismogenic depth and seismic coupling are important inputs into seismic hazard estimates. Although the importance of seismic coupling is often overlooked, it significantly impacts seismic hazard results. We present an estimation of upper and lower seismogenic depth and expected hypocentral depth and seismic coupling in the transition zone between the Alps, Dinarides and Pannonian Basin, characterized by a complex deformation pattern, highly variable crustal thickness, and moderate seismic hazard, supporting the development of the 2021 seismic hazard model of Slovenia. The hazard model was based on three seismic source models: area source model, fault source model and smoothed seismicity (point) source model. We estimated the lower seismogenic depth using seismological and geological data and compared them. The seismological estimate was based on two regional earthquake catalogues prepared for this study. In the area source model, estimates of lower seismogenic depth from seismological data are deeper or equal to the ones derived from geological data, except in one case. In the fault source model, we analysed each fault individually and chose seismological lower depth estimates in 12 among 89 faults as more representative. The seismogenic thickness for each individual fault source was determined for seismic coupling determination. The seismic coupling was assessed by two approaches, i.e. we chose the most trusted value from the literature, and the value determined for each fault individually by using the approach based on the updated regional fault and earthquake data sets. The final estimate of seismic coupling ranges from 0.77 to 0.38. We compared the tectonic moment rate based on long-term slip rate using different values of seismic coupling with the seismic moment rate obtained from the earthquake catalogue. The analysis is done for the whole area, as well as for the individual area zones. The analysis of N–S components of estimated slip for the largest faults in the area of west Slovenia shows that the regional geological and geodetic shortening rates are comparable. The total activity rate of three global seismic source models is compared, which gives up to a 10 % difference. Our results contribute to a better understanding of the seismic activity in the region. The presented approach for seismic coupling estimation can be applied in cases where the total slip rate is given instead of its seismic part and can be used at regional or national level. The approach is also suitable for the cross-border harmonization of the European seismic hazard modelling data.

A probabilistic seismic hazard model for Greenland

A systematic overview and comparison is presented on the seismic hazard assessment based on the observations and seismic hazard model and the characteristics of earthquake ground motions for a site, a local area, and a region. It shows that the seismic hazard estimated by directly using the observations could differ from that evaluated using an adopted seismic hazard model. It indicates the importance to judiciously select the seismic hazard model, as well as to understand that historical records for a limited period may not fully reflect the seismic hazard. The comparison of the ground motion characteristics is focused on the variability of the ground motion measures, the coherency for record components in two orthogonal orientations, and the spatial correlation and spatial coherency. Procedures for simulating bidirectional excitations at a site and record components at multiple sites for a scenario seismic event are given. The application of the simulated record components to estimate the seismic loss for a portfolio of hypothetical buildings by considering a scenario event is shown, indicating the effectiveness of the presented methodology for seismic loss estimation.

We construct a probabilistic seismic hazard model for mainland China by integrating historical earthquakes, active faults, and geodetic strain rates. We delineate large seismic source zones based on geologic and seismotectonic characteristics. For each source zone, a tapered Gutenberg–Richter (TGR) distribution is used to model the total seismic activity rates. The TGR a ‐ and b ‐values are calculated using a new earthquake catalog, while corner magnitudes are constrained using the seismic moment rate inferred from a geodetic strain rate model. For hazard calculations, the total TGR distribution is split into two parts, with smaller ( M W < 6.5) earthquakes being distributed within the zone using a smoothed seismicity method, and larger earthquakes put both onto active faults, based on fault slip rates and dimensions, and into the zone as background seismicity. We select ground motion models by performing residual analysis using ground motion recordings. Site amplifications are considered based on a site condition map developed using geology as a proxy. The resulting seismic hazard is consistent with the fifth‐generation national seismic hazard model for most major cities.

Summary The southern Pacific Islands region is highly seismically active, and includes earthquakes from four major subduction systems, seafloor fracture zones and transform faults, and other sources of crustal seismicity. Since 1900, the area has experienced >350 earthquakes of M > 7.0, including 11 of M ≥ 8.0. Given the elevated threat of earthquakes, several probabilistic seismic hazard analyses have been published for this region or encompassed subregions; however, those that are publicly accessible do not provide complete coverage of the region using homogeneous methodologies. Here, we present a probabilistic seismic hazard model for the southern Pacific Islands that comprehensively covers the Solomon Islands in the northwest to the Tonga islands in the southeast. The seismic source model accounts for active shallow crustal seismicity with seafloor faults and gridded smoothed seismicity, subduction interfaces using faults with geometries defined based on geophysical datasets and models, and intraslab seismicity modelled by a set of ruptures that occupy the slab volume. Each source type is assigned occurrence rates based on sub-catalogues classified to each respective tectonic context. Subduction interface and crustal fault occurrence rates also incorporate a tectonic component based on their respective characteristic earthquakes. We demonstrate the use of non-standard magnitude-frequency distributions to reproduce the observed occurrence rates. For subduction interface sources, we use various versions of the source model to account for epistemic uncertainty in factors impacting the maximum magnitude earthquake permissible by each source, varying the interface lower depth and segmentation as well as the magnitude scaling relationship used to compute the maximum magnitude earthquake and subsequently its occurrence rate. The ground motion characterisation uses a logic tree that weights three ground motion prediction equations for each tectonic region. We compute hazard maps for 10% and 2% probability of exceedance in 50 years on rock sites, discussing the regional distribution of peak ground acceleration and spectral acceleration with a period of 1.0 s, honing in on the hazard curves and uniform hazard spectra of several capital or populous cities and drawing comparisons to other recent hazard models. The results reveal that the most hazardous landmasses are the island chains closest to subduction trenches, as well as localised areas with high rates of seismicity occurring in active shallow crust. We use seismic hazard disaggregation to demonstrate that at selected cities located above subduction zones, the PGA with 10% probability of exceedance in 50 years is controlled by Mw > 7.0 subduction interface and intraslab earthquakes, while at cities far from subduction zones, Mw < 6.5 crustal earthquakes contribute most. The model is used for southern Pacific Islands coverage in the Global Earthquake Model Global Hazard Mosaic.

The spatial complexity of continental deformation in the greater Tibetan Plateau region can be defined as the extent to which relative motion of the Indian and Asian plates is partitioned between localized slip on major faults and distributed deformation. Potency rates provide a quantitative metric for determining the magnitudes of diffuse and on-fault crustal deformation, which are proportional to strain rates within crustal micro-plates and fault slip rates, respectively. We simultaneously estimate micro-plate rotation rates, interseismic elastic strain accumulation, fault slip rates on major structures, and strain rates within 24 tectonic micro-plates inferred from active fault maps in the greater Tibetan Plateau region using quasi-static block models constrained by interseismic surface velocities at 731 GPS sites and 9 Holocene–Late Quaternary geologic fault slip rates. The joint geodetic–geologic inversion indicates that geologic slip rates are kinematically consistent with differential micro-plate motions. Estimated left-lateral slip rates on the Altyn Tagh, west-central Kunlun, and Xianshuihe faults are relatively homogeneous along strike (~ 11.5, 10.5, and 11 mm/yr, respectively) while segmentation of the eastern Kunlun fault by the intersecting Elashan and Riyueshan faults results in a decreased slip rate, consistent with geologic observations. The fraction, ϕ, of total potency rate associated with intrablock strain, uncorrected for observational noise, ranges from 0.27 in the Himalayan Range block to 0.91 in the Aksai Chin block. Monte Carlo simulations are used to quantify the likelihood that internal deformation is statistically distinguishable from the uncertainties in geodetic velocities. These simulations indicate that internal block deformation is statistically significant only within the Himalayan Range Front (where internal deformation accounts for ϕ ID = 0.11 of block potency rate budget), west-central plateau ( ϕ ID = 0.68), Ganzi-Yushu/Xianshuihe (0.58), Burma (0.09), Jiali (0.38), and Aksai Chin (0.68) blocks. In the other 18 tectonic micro-plates within the plateau region, estimated internal block potency is not currently distinguishable from the expected contribution of observational noise to residual velocities. Of the total potency budget within the Tibetan Plateau, 85% is taken up by slip on major faults, with the remaining 15% accommodated by internal processes at sub-block scale distinguishable from observational noise. The localization of the majority of plate boundary activity is also supported by the spatial distribution of modern and historical crustal earthquakes. Sixty-seven percent of the total moment released by earthquakes in the CMT catalog and 90% of historical moment since 1900 have been released within 25 km of the major faults included in the block model, representing only 12% of the characteristic half-block length scale of ~ 215 km. The localization of deformation inferred from geologic, geodetic, and seismic observations suggests that forces applied to tectonic micro-plates drive fault system activity at the India–Asia collision zone over decadal to Quaternary time scales.

Estimating the Gutenberg–Richter b ‐value from seismic catalogs is critical for earthquake forecasting and hazard assessment. However, traditional approaches rely on predefined magnitude thresholds and are highly sensitive to catalog incompleteness, limiting their applicability in automated or real‐time settings. We propose a novel, unsupervised inference framework that estimates the b ‐value directly from the distribution of positive magnitude differences , without requiring manual threshold tuning. By introducing a two‐parameter probabilistic model, we account for deviations from the ideal exponential form due to spatial and temporal variations in detection capability. This formulation enables a robust and scalable likelihood‐based estimation of both the b ‐value and a correction factor , which quantifies incompleteness. We validate our algorithm using synthetic catalogs generated from the ETAS model under varying noise and detection conditions, and apply it to global instrumental data sets from five tectonically active regions: Italy, Japan, Southern California, Northern California, and New Zealand. The results demonstrate high accuracy, robustness to incomplete data, and strong potential for integration into machine learning pipelines for seismic monitoring and hazard modeling.

Editorial| March 01, 2012 Earthquake Hazard Maps and Objective Testing: The Hazard Mapper’s Point of View Mark W. Stirling Mark W. Stirling GNS Science P.O. Box 30368 Lower Hutt, New Zealandm.stirling@gns.cri.nz Search for other works by this author on: GSW Google Scholar Seismological Research Letters (2012) 83 (2): 231–232. https://doi.org/10.1785/gssrl.83.2.231 Article history first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Mark W. Stirling; Earthquake Hazard Maps and Objective Testing: The Hazard Mapper’s Point of View. Seismological Research Letters 2012;; 83 (2): 231–232. doi: https://doi.org/10.1785/gssrl.83.2.231 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySeismological Research Letters Search Advanced Search The recent SRL Opinion article titled “Bad Assumptions or Bad Luck: Why Earthquake Hazard Maps Need Objective Testing,” by Seth Stein, Robert Geller, and Mian Liu (SRL 82(5), 623–626) suggests that probabilistic seismic hazard (PSH) models have been inadequate in terms of forecasting recent devastating earthquakes, and expresses a need for objective testing of these models. This response comes from the perspective of a hazard mapper. First, I’d like to clarify that the PSH models referred to by Stein and his colleagues are not forecasting tools. They are tools developed to provide estimates of hazard for long return periods... You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

We present a new probabilistic seismic hazard model for the Canterbury region, the model superseding the earlier model of Stirling et al. (1999, 2001). The updated model incorporates new onshore and offshore fault data, new seismicity data, new methods for the earthquake source parameterisation of both datasets, and new methods for estimation of the expected levels of Modified Mercalli Intensity (MMI) across the region. While the overall regional pattern of estimated hazard has not changed since the earlier seismic hazard model, there have been slight reductions in hazard in some areas (western Canterbury Plains and eastern Southern Alps), coupled with significant increases in hazard in one area (immediately northeast of Kaikoura). The changes to estimated acceleration for the new versus older model serve to show the extent that major changes to a multidisciplinary source model may impact the final estimates of hazard, while the new MMI estimates show the added impact of a new methodology for calculating MMI hazard.

Finland, which is characterized by very low seismicity, does not have a national seismic hazard map. However, site specific Probabilistic Seismic Hazard Assessments (PSHAs) for critical infrastructure, including nuclear power plants (NPPs), have been conducted. The sophisticated 2020 European Seismic Hazard Model (ESHM20) offers several advancements that could influence seismic hazard work in stable continental regions like Finland.  As part of the SEISMIC RISK collaborative project involving the University of Helsinki, VTT Technical Research Centre of Finland, and the Geological Survey of Finland, a national PSHA model has been developed. The model is based on a Fennoscandian earthquake catalogue – FENCAT, compiled from Nordic national catalogues based on the observations from the national seismic networks. This allows for calculation of the recurrence parameters with lower magnitudes than the ESHM20. Although a preliminary comparison reveals only minor local differences at hazard levels, a more detailed examination at critical infrastructure sites is necessary. We have compared the regional hazard results obtained within the SEISMIC RISK project and hazard values of the ESHM20 at two NPP sites in Finland. Four criteria from the literature, compiled by Douglas et al. (2023), were employed for assessing the differences between the seismic hazard models. To this end, the mean, median, and 16th and 84th fractiles for the ESHM20 were obtained from the European Facilities for Earthquake Hazard and Risk (EFEHR) database hosted by EPOS–Seismology. A visual inspection of the hazard curves initially indicated consistently higher mean hazards from the Finnish model at the NPP sites compared to ESHM20. The lognormal distributions of the hazard models were estimated, and the differences were assessed for the return periods of 106, 104, 5000, 2475, and 475 years using the four criteria. The distributions revealed a significantly smaller standard deviation for the Finnish model than for the ESHM20. When comparing the two models, the mean Annual Frequency of Exceedance (AFE) changed by over 25% for the ground-motions corresponding to AEFs ≤ 10-4 and by more than 35% for ground-motions corresponding to 10-6 AFE. These findings underline the significant differences between the models.  In summary, a minimum of two out of the four criteria are met at one of the NPP sites, and at the other NPP site, three out of four criteria are satisfied. This further highlights the significance of the differences between the ESHM20 and the Finnish hazard model. Nevertheless, while the observed change in hazard between the Finnish hazard model and the ESHM20 can be deemed substantial, it does not justify the use of the Finnish hazard model for the longer return periods. Further investigations, such as site-specific hazard assessments, are necessary for the return periods relevant to NPPs.        Douglas, J., Crowley, H., Silva, V., Marzocchi, W., Danciu, L., & Pinho, R. (2023). Methods for evaluating the significance and importance of differences amongst probabilistic seismic hazard results for engineering and risk analyses: A review and insights. EGUsphere [preprint], https://doi.org/10.5194/egusphere-2023-991 

Over the past two decades, seismic hazard modeling has advanced along two complementary frontiers: empirical probabilistic frameworks, which systematically capture uncertainty through statistical inference, and physics-based simulation platforms, which directly compute ground motions from the governing equations of wave propagation. This project seeks to unify these two worlds by developing an end-to-end integration between OpenQuake and CyberShake, thereby creating a new generation of seismic hazard models that are globally extensible, probabilistically complete, and physically consistent. CyberShake has been under active development for more than a decade, demonstrating its robustness and scientific maturity through extensive implementations in California. It performs a physics-based probabilistic seismic hazard analysis (PSHA), replacing traditional empirical Ground Motion Prediction Equations (GMPEs) with full 3D numerical simulations of seismic wave propagation. Built upon the UCERF2/3 Earthquake Rupture Forecasts, CyberShake computes hazard curves directly from synthetic seismograms generated via Strain Green’s Tensors and thousands of stochastic rupture variations. This approach enables non-ergodic, site-specific hazard estimation and has set a global benchmark for high-fidelity hazard computation. However, its application has remained geographically limited: both the ERF and 3D velocity models were designed specifically for California, requiring extensive datasets that are rarely available elsewhere. Conversely, OpenQuake, developed by the Global Earthquake Model (GEM) Foundation, provides a fully open-source, Python-based framework for probabilistic seismic hazard and risk analysis. It serves as the computational backbone of large-scale hazard models such as the European Seismic Hazard Model 2020 (ESHM20), which integrates decades of regional expertise into a unified and statistical representation. OpenQuake provides a complete probabilistic framework to build Earthquake Rupture Forecasts (ERFs) that combine declustered catalogs, background seismicity, and multi-branch logic trees, ensuring a balanced and uncertainty-aware representation of regional tectonics. Furthermore, its ecosystem extends seamlessly to vulnerability and exposure modules, enabling the translation of hazard into actionable risk assessments and resilience planning.This project will establish a direct pipeline from OpenQuake’s event-based results to the generation of an ERF compatible with CyberShake’s simulation framework, ensuring moment–rate consistency. By doing so, it will enable CyberShake simulations to be performed for regions beyond California, extending its use to Europe based on the knowledge contained in the ESHM20. The first pilot region is Istanbul, Turkey, a densely populated metropolis located near the western termination of the North Anatolian Fault. Our initial results show that the workflow is already functioning at the prototype level: we have developed a unified 3D velocity model for the Istanbul region by combining available tomographic models with local datasets; generated preliminary event-based rupture catalogs from ESHM20 using OpenQuake; and demonstrated early convergence behavior in hazard curves, indicating that the rupture sampling strategy is statistically robust. These initial results demonstrate the feasibility of the integration approach and indicate that the essential elements needed for a CyberShake-ready ERF are already in place.

Southeast Spain experiences relatively low seismicity rates, characterized by slow seismic deformation. However, historical records highlight the significant impact of moderate to large earthquakes on local communities, such as the 1518 Vera (Almería) earthquake (Mw 6.4) and the 2011 Lorca earthquake (Mw 5.2). Thus, such events pose a considerable seismic risk to the region, in spite of their infrequent occurrence. Given the lack of comprehensive data on this kind of seismic events, this study contributes towards a physics-based seismic hazard model for Southeast (SE) Spain. Specifically, we first develop a broad earthquake rupture forecast (ERF) model that includes potential single- and multi-fault events, and then we use Cybershake to model the maximum-magnitude expected earthquakes along the various fault systems in the region, to obtain 0-1 Hz ground motion simulations. In this ERF model, we integrate a vast amount of regional geological data, including the Quaternary-Active Faults Database of Iberia, historical seismic catalogs, and available paleoseismic data as well. Using Cybershake, a high-performance computing earthquake-modeling platform originally designed for Southern California, we simulate ground-motion time histories from pseudo-dynamic kinematic rupture scenarios on three-dimensional finite faults. Our simulations consider a recently-available tomographic 3D velocity model, but for completeness, we also perform simulations using a 1D average model and explore the differences on the resulting synthetic ground motions. This approach allows to create physics-based rupture scenarios and shake maps, offering an alternative seismic hazard model tailored to SE Spain and setting the basis to update regional seismic hazard assessments. The results provide valuable insights into potentially harmful multi-fault events and scenarios in slow-deforming tectonic settings, contributing to more accurate seismic hazard and risk maps, and informing effective planning, decision-making and response strategies in the region.

The paper presents a framework for the vulnerability analysis to assess seismic risk for the Republic of Georgia. Firstly, detailed inventory map of elements at risk was created. Here elements at risk are comprised of buildings and population. The grid of 0.025° size was created to summarize building and population data into the grid cells for further analysis. The custom programming script was created that summarizes the following information for each grid cell: the total number of buildings, total area of buildings, total population, total number of buildings per each taxonomy class and total area of buildings for each taxonomy class. Secondly, seismic hazard maps were calculated based on modern approach of selecting and ranking global and regional ground motion prediction equation for region. Thirdly, on the bases of empirical data that was collected for some earthquake intensity based vulnerability study were completed for Georgian buildings. Finally, probabilistic seismic risk assessment in terms of structural damage and casualties were calculated for the territory of Georgia for 2.8 km grid cells using obtained results. This methodology gave prediction of damage and casualty for a given probability of recurrence, based on a probabilistic seismic hazard model, population distribution, inventory, and vulnerability of buildings.