Seismic Hazard Model Research Articles

An Assessment of Earthquake Scaling Relationships for Crustal Earthquakes in Indonesia

AbstractTo estimate the hazard posed by active faults, estimates of the maximum magnitude earthquake that could occur on the fault are needed. I compare previously published scaling relationships between earthquake magnitude and rupture length with data from recent earthquakes in Indonesia. I compile a total amount of 13 literatures on investigating coseismic deformation in Indonesia, which then divided into strike-slip and dip-slip earthquake cases. I demonstrate that a different scaling relationship generates different misfit compared to data. For a practical practice of making seismic hazard model in Indonesia, this research shows the suggested reference for a scaling relationship of strike-slip and dip-slip faulting regime. On a practical approach in constructing a logic tree for seismic hazard model, using different weighting between each published earthquake scaling relationship is recommended.

Interoccurrence times and seismic hazard for upper-crustal volcanic chain earthquakes in El Salvador: are they Poissonian distributed?

We study the statistical properties of time intervals between successive earthquakes for a given magnitude in the El Salvador volcanic chain, namely hereafter the interoccurrence times employing both the cumulative Poisson and the Weibull probability distributions. The dataset comprises magnitudes between M 4.0 and 6.93 within the years 1528–2018. We suggest that ITs pose the Weibull distribution for all events and that the Poisson distribution co-exists for ITs longer than the Weibull mean. Based on the probabilities distribution fit, we compute for engineering purposes ground motion and elastic response spectra for 5% damping employing time-dependent and independent seismic hazard models at San Salvador city, observing covariance of less than 7% amongst the models. The disaggregation analysis suggests that a magnitude 6.3 contributes most to the hazard and coincides with the magnitude bin of 6.25–6.50, which has the maximum conditional probability in the time-dependent model.

Fault-Source-Based Probabilistic Seismic Hazard and Risk Analysis for Victoria, British Columbia, Canada: A Case of the Leech River Valley Fault and Devil’s Mountain Fault System

This study develops a fault-source-based seismic hazard model for the Leech River Valley Fault (LRVF) and the Devil’s Mountain Fault (DMF) in southern Vancouver Island, British Columbia, Canada. These faults pose significant risks to the provincial capital, Victoria, due to their proximity and potentially large earthquake magnitudes. To evaluate the effects of including these faults in probabilistic seismic hazard analysis and city-wide seismic loss estimation for Victoria, a comprehensive sensitivity analysis is conducted by considering different fault rupture patterns and different earthquake magnitude models, as well as variations in their parameters. The aim is to assess the relative contributions of the LRVF-DMF system to the overall seismic hazard and risk in Victoria at different return periods. The consideration of the LRVF-DMF system as a potential seismic source increases the seismic risk assessment results by 10 to 30%, especially at the high return period levels. The sensitivity analysis results highlight the importance of determining the slip rate for the fault deformation zone and of specifying the earthquake magnitude models (e.g., characteristic versus truncated exponential models). From urban seismic risk management perspectives, these nearby faults should be considered critical earthquake scenarios.

The 2018 update of the US National Seismic Hazard Model: Where, why, and how much probabilistic ground motion maps changed

The 2018 US Geological Survey National Seismic Hazard Model (NSHM) incorporates new data and updated science to improve the underlying earthquake and ground motion forecasts for the conterminous United States. The NSHM considers many new data and component input models: (1) new earthquakes between 2013 and 2017 and updated earthquake magnitudes for some earlier earthquakes; (2) two updated smoothed seismicity models to forecast earthquake rates; (3) two suites of new central and eastern US (CEUS) ground motion models (GMMs) to translate ground shaking for various earthquake sizes and source-to-site distances considered in the model; (4) two CEUS GMMs for aleatory variability; (5) two CEUS site-effect models that modify ground shaking based on alternative shallow site conditions; (6) more advanced western US (WUS) lithologic and structural information to assess basin site effects for selected urban regions; and (7) a more comprehensive range of outputs (22 periods and 8 site classes) than in previous versions of the NSHMs. Each of these new datasets and models produces changes in the probabilistic ground shaking levels that are spatially and statistically analyzed. Recent earthquakes or changes to some older earthquake magnitudes and locations mostly result in probabilistic ground shaking levels that are similar to previous models, but local changes can reach up to +80% and −60% compared to the 2014 model. Newly developed CEUS models for GMMs, aleatory variability, and site effects cause overall changes up to ±64%. The addition of the WUS basin amplifications causes changes of up to +60% at longer periods for sites overlying deep soft soils. Across the conterminous United States, the hazard changes in the model are mainly caused by new GMMs in the CEUS, by sedimentary basin effects for long periods (≥1 s) in the WUS, and by seismicity changes for short (0.2 s) and long (1 s) periods for both areas.

Life-cycle probabilistic seismic risk assessment of high-rise buildings considering carbonation induced deterioration

The geometrical and mechanical properties of reinforcing steels embedded in the RC structures may be deteriorated due to the aggressive environments, such as the carbonation, chloride, and wind-induced fatigue. The joint effects of aging and seismic load on the response of high-rise buildings are always neglected in current structural design specifications. This paper presents a probabilistic methodology to assess the time-dependent annual damage probability considering the carbonation-induced corrosion and the uncertainties associated with random variables under seismic excitations, which is implemented in a 42-story steel frame-RC core tube building. The loss of cross-sectional area and reduction in strength of reinforcements are considered in the analysis for the serviceability and safety limit states. The seismic hazard model and conditional fragility are integrated to compute the total annual damage probability of this building at different aging scenarios. Numerical results indicate that the carbonation-induced corrosion in reinforcements has significant impacts on the structural performances during its lifetime under both the serviceability and safety limit states. Neglecting the influences of deterioration may lead to erroneous predictions of damage probabilities for corroded high-rise buildings. The application of this study highlights the necessity of comprehensively discussing the detrimental effects of harsh environments on high-rise buildings, which may be neglected in the available literature.

Toward Physics-Based Nonergodic PSHA: A Prototype Fully Deterministic Seismic Hazard Model for Southern California

ABSTRACT We present a nonergodic framework for probabilistic seismic-hazard analysis (PSHA) that is constructed entirely of deterministic, physical models. The use of deterministic ground-motion simulations in PSHA calculations is not new (e.g., CyberShake), but prior studies relied on kinematic rupture generators to extend empirical earthquake rupture forecasts. Fully dynamic models, which simulate rupture nucleation and propagation of static and dynamic stresses, are still computationally intractable for the large simulation domains and many seismic cycles required to perform PSHA. Instead, we employ the Rate-State earthquake simulator (RSQSim) to efficiently simulate hundreds of thousands of years of M≥6.5 earthquake sequences on the California fault system. RSQSim produces full slip-time histories for each rupture, which, unlike kinematic models, emerge from frictional properties, fault geometry, and stress transfer; all intrinsic variability is deterministic. We use these slip-time histories directly as input to a 3D wave-propagation code within the CyberShake platform to obtain simulated Fmax=0.5 Hz ground motions. The resulting 3 s spectral acceleration ground motions closely match empirical ground-motion model (GMM) estimates of median and variability of shaking. When computed over a range of sources and sites, the variability is similar to that of ergodic GMMs. Variability is reduced for individual pairs of sources and sites that repeatedly sample a single path, which is expected for a nonergodic model. This results in increased exceedance probabilities for certain characteristic ground motions for a source–site pair, while decreasing probabilities at the extreme tails of the ergodic GMM predictions. We present these comparisons and preliminary fully deterministic physics-based RSQSim–CyberShake hazard curves, as well as a new technique for estimating within- and between-event variability through simulation.

Style of faulting of expected earthquakes in Italy as an input for seismic hazard modeling

Abstract. The style of faulting and distributions of nodal planes are essential input for probabilistic seismic hazard assessment. As part of a recent elaboration of a new seismic hazard model for Italy, we defined criteria to parameterize the styles of faulting of expected earthquake ruptures and to evaluate their representativeness in an area-based seismicity model. Using available seismic moment tensors for relevant seismic events (Mw≥4.5), first arrival focal mechanisms for less recent earthquakes, and also geological data on past activated faults, we collected a database for the last ∼100 years by gathering a thousand data points for the Italian peninsula and regions around it. In this dataset, we adopted a procedure that consists, in each seismic zone, of separating the available seismic moment tensors into the three main tectonic styles, making a summation within each group, identifying possible nodal plane(s), taking into account the different percentages of styles of faulting, and including where necessary total or partial (even in terms of tectonic style) random source contributions. Referring to the area source model used, for several seismic zones we obtained robust results; e.g., along the central and southern Apennines we expect future earthquakes to be mostly extensional, although in the outer part of the chain reverse and strike-slip events are possible. In the northern part of the Apennines we expect different styles of faulting for different hypocentral depths. In zones characterized by a low seismic moment release, the possible style of faulting of future earthquakes is less clear and it has been represented using different combinations of random sources. The robustness of our results is confirmed when compared with recent relevant earthquakes occurring in Italy.

The 2018 update of the US National Seismic Hazard Model: Additional period and site class data

As part of the update of the 2018 National Seismic Hazard Model (NSHM) for the conterminous United States (CONUS), new ground motion and site effect models for the central and eastern United States were incorporated, as well as basin depths from local seismic velocity models in four western US (WUS) urban areas. These additions allow us, for the first time, to calculate probabilistic seismic hazard curves for an expanded set of spectral periods (0.01 to 10 s) and site classes (VS30 = 150 to 1500 m/s) for the CONUS, as well as account for amplification of long-period ground motions in deep sedimentary basins in the Los Angeles, San Francisco Bay, Seattle, and Salt Lake City areas. Two sets of 2018 NSHM hazard data (hazard curves and uniform-hazard ground motions) are available: (1) 0.05°-latitude-by-0.05°-longitude gridded data for the CONUS and (2) higher resolution 0.01°-latitude-by-0.01°-longitude gridded data for the four WUS basins. Both sets of data contain basin effects in the WUS deep sedimentary basins. Uniform-hazard ground motion data are interpolated for 2, 5, and 10% probability of exceedance in 50 years from the hazard curves. The gridded data for the hazard curves and uniform-hazard ground motions, for all periods and site classes, are available for download at the U.S. Geological Survey ScienceBase Catalog ( https://doi.org/10.5066/P9RQMREV ). The design ground motions derived from the hazard curves have been accepted by the Building Seismic Safety Council for adoption in the 2020 National Earthquake Hazard Reduction Program Recommended Seismic Provisions.

Development of risk-targeted seismic hazard maps for the Iranian plateau

This study aims to provide the risk-targeted seismic design maps and corresponding adjusting coefficients for different intensity measures on the Iranian plateau, using the iterative risk integral approach. The main purpose of this study is to provide the risk-targeted hazard maps with a uniform level of risk based on an acceptable collapse probability and risk threshold. The investigation applies the most recent and notable seismic hazard model for the studied region, namely the Earthquake Hazard Model of the Middle East (EMME). Having done the preprocessing procedures for characterizing the possible bias in the input data, hazard curves on 0.1° grids were extracted from the median values of the logic tree of the EMME model. Utilizing the deliberately rational values of the required parameters by the risk-targeting approach, i.e. 2% exceedance probability in 50 years as the 10% quantile of the fragility function, leads to reach some multiple uniform seismic risk maps with 1% probability of collapse in 50 years for each intensity measure. The imaginable inconsistency of the maps with historical data (as a picture of reality) has also been assessed in terms of underestimations or overestimations, using a two-sided statistical test at a 95% confidence level. The outcome of this study can be incorporated in the next revision of the national seismic code for a more reliable and robust seismic design of building structures.

PSHA of the southern Pacific Islands

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.

Evaluation of Seismic Hazard Models with Fragile Geologic Features

AbstractWe provide an overview of a 2019 workshop on the use of fragile geologic features (FGFs) to evaluate seismic hazard models. FGFs have been scarcely utilized in the evaluation of seismic hazard models, despite nearly 30 yr having passed since the first recognition of their potential value. Recently, several studies have begun to focus on the implementation of FGFs in seismic hazard modeling. The workshop was held to capture a “snapshot” of the state-of-the-art in FGF work and to define key research areas that would increase confidence in FGF-based evaluation of seismic hazard models. It was held at the annual meeting of the Southern California Earthquake Center on 8 September 2019, and the conveners were Mark Stirling (University of Otago, New Zealand) and Michael Oskin (University of California, Davis). The workshop attracted 44 participants from a wide range of disciplines. The main topics of discussion were FGF fragility age estimation (age at which an FGF achieved its current fragile geometry), fragility estimation, FGF-based evaluation of seismic hazard models, and ethical considerations relating to documentation and preservation of FGFs. There are now many scientists working on, or motivated to work on, FGFs, and more types of FGFs are being worked on than just the precariously balanced rock (PBR) variety. One of the ideas presented at the workshop is that fragility ages for FGFs should be treated stochastically rather than assuming that all share a common age. In a similar vein, new studies propose more comprehensive methods of fragility assessment beyond peak ground acceleration and peak ground velocity-based approaches. Two recent studies that apply PBRs to evaluate probabilistic seismic hazard models use significantly different methods of evaluation. Key research needs identified from the workshop will guide future, focused efforts that will ultimately facilitate the uptake of FGFs in seismic hazard analysis.

Challenges and opportunities in New Zealand seismic hazard and risk modeling using OpenQuake

The corrected 2010 New Zealand National Seismic Hazard Model has been adapted for use in the Global Earthquake Model’s OpenQuake engine through an extensive benchmarking exercise with GNS Science’s legacy Fortran code. Resolution of differences between the legacy code and OpenQuake result in hazard curve output comparisons with discrepancies of less than 3% nationally and remaining discrepancies highlight challenges faced when moving away from in-house legacy code. OpenQuake’s multiple and varied computation options for both hazard and risk and OpenQuake’s consistent, software-friendly output formats allow for exploration and development of innovative approaches to future seismic hazard and risk modeling in New Zealand. The end-to-end seismic hazard-to-risk capabilities already enabled by the inclusion of New Zealand seismic hazard, vulnerability, and building exposure models in OpenQuake have already had significant impact on post-disaster response to the 2016 Kaikōura earthquake.

Seismic Hazard Analyses From Geologic and Geomorphic Data: Current and Future Challenges

AbstractThe loss of life and economic consequences caused by several recent earthquakes demonstrate the importance of developing seismically safe building codes. The quantification of seismic hazard, which describes the likelihood of earthquake‐induced ground shaking at a site for a specific time period, is a key component of a building code, as it helps ensure that structures are designed to withstand the ground shaking caused by a potential earthquake. Geologic or geomorphic data represent important inputs to the most common seismic hazard model (probabilistic seismic hazard analyses, or PSHAs), as they can characterize the magnitudes, locations, and types of earthquakes that occur over long intervals (thousands of years). However, several recent earthquakes and a growing body of work challenge many of our previous assumptions about the characteristics of active faults and their rupture behavior, and these complexities can be challenging to accurately represent in PSHA. Here, we discuss several of the outstanding challenges surrounding geologic and geomorphic data sets frequently used in PSHA. The topics we discuss include how to utilize paleoseismic records in fault slip rate estimates, understanding and modeling earthquake recurrence and fault complexity, the development and use of fault‐scaling relationships, and characterizing enigmatic faults using topography. Making headway in these areas will likely require advancements in our understanding of the fundamental science behind processes such as fault triggering, complex rupture, earthquake clustering, and fault scaling. Progress in these topics will be important if we wish to accurately capture earthquake behavior in a variety of settings using PSHA in the future.

Probabilistic seismic risk assessment of India

This study presents a comprehensive open probabilistic seismic risk model for India. The proposed model comprises a nationwide residential and non-residential building exposure model, a selection of analytical seismic vulnerability functions tailored for Indian building classes, and the open implementation of an existing probabilistic seismic hazard model for India. The vulnerability of the building exposure is combined with the seismic hazard using the stochastic (Monte Carlo) event-based calculator of the OpenQuake engine to estimate probabilistic seismic risk metrics such as average annual economic losses and the exceedance probability curves at the national, state, district, and subdistrict levels. The risk model and the underlying datasets, along with the risk metrics calculated at different scales, are intended to be used as tools to quantitatively assess the earthquake risk across India and also compare with other countries to develop risk-informed building design guidelines, for more careful land-use planning, to optimize earthquake insurance pricing, and to enhance general earthquake risk awareness and preparedness.

Portfolio Seismic Loss Estimation and Risk-based Critical Scenarios for Residential Wooden Houses in Victoria, British Columbia, and Canada.

This study presents a city-wide seismic risk assessment of single-family wooden houses in Victoria, British Columbia, and Canada. The novelty and uniqueness of this study include considerations of detailed building-by-building exposure model for residential houses, current national seismic hazard model for Canada, and rigorous seismic fragility modeling of wooden houses based on nonlinear dynamic analysis of structures subjected to mainshock-aftershock sequences. A full consideration of stochastic event scenarios in probabilistic seismic risk analysis allows the identification of critical scenarios from overall regional seismic risk perspectives and provides valuable insights in informing earthquake disaster risk management actions. Outputs from the developed catastrophe model for Victoria are compared with the empirical model that was developed based on insurance claim data from the 1994 Northridge earthquake. Results of the seismic loss calculations highlight the importance of seismic resistance of the existing houses and of aftershock effects. The integrated use of the outputs from the advanced catastrophe model facilitates risk-based identification of critical earthquake scenarios, which are useful for different stakeholders for earthquake risk management purposes.

Cost\u2013benefit analyses to assess the potential of Operational Earthquake Forecasting prior to a mainshock in Europe

In the past couple of decades, Operational Earthquake Forecasting (OEF) has been proposed as a way of mitigating earthquake risk. In particular, it has the potential to reduce human losses (injuries and deaths) by triggering actions such as reinforcing earthquake drills and preventing access to vulnerable structures during a period of increased seismic hazard. Despite the dramatic increases in seismic hazard in the immediate period before a mainshock (of up to 1000 times has been observed), the probability of a potentially damaging earthquake occurring in the coming days or weeks remains small (generally less than 5%). Therefore, it is necessary to balance the definite cost of taking an action against the uncertain chance that it will mitigate earthquake losses. In this article, parametric cost–benefit analyses using a recent seismic hazard model for Europe and a wide range of inputs are conducted to assess when potential actions for short-term OEF are cost–beneficial prior to a severe mainshock. Ninety-six maps for various combinations of input parameters are presented. These maps show that low-cost actions (costing less than 1% of the mitigated losses) are cost–beneficial within the context of OEF for areas of moderate to high seismicity in the Mediterranean region. The actions triggered by OEF in northern areas of the continent are, however, unlikely to be cost–beneficial unless very large increases in seismicity are observed or very low-cost actions are possible.

Hazardous faults of South America; compilation and overview

The heterogeneous South American geology has coined a wide variety of neotectonic settings where crustal seismogenic sources do occur. This fact has led to different approaches for mapping and inventory neotectonic structures. The South American Risk Assessment project promoted the discussion and update under uniform standards of the available information on neotectonic deformation, for its application in regional Probabilistic Seismic Hazard Assessments. As a result, 1533 hazardous faults have been inventoried onshore South America, 497 of them qualifying to feed the engine model driving probabilistic maps.Main hazardous structures are concentrated throughout the eastern boundary of the Northern Andean Sliver and along the foreland-facing Andean Thrust Front. Space geodesy and seismicity illuminate the seismogenic significance of these deformation belts, although few neotectonic surveys have been conducted to date in the latter region. The characteristics of the main structures or deformation zones are here outlined according to their filiation to neotectonic domains, which are dependant on the geologic, seismotectonic, or morphotectonic settings in Andean and extra-Andean regions.The knowledge accrued on the hazardous faults in South America here compiled, reinforces the fact that some of these structures constitute significant hazard sources for many urban areas and critical facilities and should be incorporated in seismic hazard assessments. However, the available fault data are insufficient in many cases or carry significant epistemic uncertainties for fault source characterization. This contribution aims to summarize the present knowledge on the South American hazardous faults as well as the main challenges for successful fault data incorporation into seismic hazard models.

A ground motion logic tree for seismic hazard analysis in the stable cratonic region of Europe: regionalisation, model selection and development of a scaled backbone approach

Regions of low seismicity present a particular challenge for probabilistic seismic hazard analysis when identifying suitable ground motion models (GMMs) and quantifying their epistemic uncertainty. The 2020 European Seismic Hazard Model adopts a scaled backbone approach to characterise this uncertainty for shallow seismicity in Europe, incorporating region-to-region source and attenuation variability based on European strong motion data. This approach, however, may not be suited to stable cratonic region of northeastern Europe (encompassing Finland, Sweden and the Baltic countries), where exploration of various global geophysical datasets reveals that its crustal properties are distinctly different from the rest of Europe, and are instead more closely represented by those of the Central and Eastern United States. Building upon the suite of models developed by the recent NGA East project, we construct a new scaled backbone ground motion model and calibrate its corresponding epistemic uncertainties. The resulting logic tree is shown to provide comparable hazard outcomes to the epistemic uncertainty modelling strategy adopted for the Eastern United States, despite the different approaches taken. Comparison with previous GMM selections for northeastern Europe, however, highlights key differences in short period accelerations resulting from new assumptions regarding the characteristics of the reference rock and its influence on site amplification.

Spatio-temporal associations between dike intrusions and fault ruptures in the Tongariro Volcanic Center, New Zealand

Crustal extension of the southern portion of the Taupo Rift in the Central North Island of New Zealand is mostly accommodated by normal faulting and rare dike intrusions. To better understand how extension is accommodated and how volcanoes and faults interact, we provide a new integration of the tectonic and volcanic history of this young section of the Taupo Rift from geological evidence. Fault acceleration and deceleration apparently coincide with episodes of voluminous volcanic eruptions during the last 100 ka. Using geological data, we detect three modes of volcano-fault interactions active during different periods: (1) increased volcanism (eruptive volume) coupled with increased fault slip-rate (e.g., 26–11 cal kyr BP); (2) increased volcanism, but decreased adjacent fault activity (e.g., 11–10 cal kyr BP Pahoka-Mangamate “unzipping” period); and (3) decreased volcanism (low rates and volumes), but increased fault slip-rate (e.g., 45–25 cal kyr BP). The availability of melt production at depth is a first-order factor controlling the geodynamic processes of coeval fault slip-rate and magma volume variations within this rift. We hypothesize that progressive shallowing of magma drives transition of mode (1) to (2); i.e., maintaining high volcanic rates but decreasing fault slip. Second-order interactions, such as stress-transfer, is modelled by simple Coulomb stress transfer scenarios to other faults and volcanoes surrounding rift elements. Our results strongly suggest that fluctuations in magma input through time strongly influence both eruption frequency and seismic cycles in volcanic rifts. Time-dependent seismic hazard models must consider the influence of magmatic processes in fault parameters (e.g. temporal slip-rate variations) in continental rifting environments.

The 2018 version of the Global Earthquake Model: Hazard component

In December 2018, at the conclusion of its second implementation phase, the Global Earthquake Model (GEM) Foundation released its first version of a map outlining the spatial distribution of seismic hazard at a global scale. The map is the result of an extensive, joint effort combining the results obtained from a collection of probabilistic seismic hazard models, called the GEM Mosaic. Together, the map and the underlying database of models provide an up-to-date view of the earthquake threat globally. In addition, using the Mosaic, a synopsis of the current state-of-practice in modeling probabilistic seismic hazard at national and regional scales is possible. The process adopted for the compilation of the Mosaic adhered to the maximum extent possible to GEM’s principles of collaboration, inclusiveness, transparency, and reproducibility. For each region, priority was given to seismic hazard models either developed by well-recognized national agencies or by large collaborative projects involving local scientists. The version of the GEM Mosaic presented herein contains 30 probabilistic seismic hazard models, 14 of which represent national or sub-national models; the remainder are regional-scale models. We discuss the general qualities of these models, the underlying framework of the database, and the outlook for the Mosaic’s utility and its future versions.