Earthquake Spectra

National Aeronautics and Space Administration Advanced Rapid Imaging Analysis (ARIA) Damage Proxy Maps (DPMs) are developed by the NASA Jet Propulsion Laboratory (NASA JPL) to identify potentially damaged areas based on interferometric coherence loss in Synthetic Aperture Radar (SAR) data. DPMs are typically based on data from Sentinel-1 satellites that orbit every 12 days, meaning that results can be provided within 1-2 weeks of an event. Although DPMs have been qualitatively validated as being able to detect surface effects of earthquakes, quantitative validations of their ability to differentiate damaged from undamaged areas and different types and levels of surface effects are lacking. We propose a framework for quantitative validation and apply it to surface fault rupture data from the 2019 Ridgecrest Earthquake sequence. The quantitative analyses take two forms: (1) the statistical distribution of a DPM index ( I DPM ) for different fault displacement ranges through box and whisker plots, and (2) empirical fragility functions that relate I DPM to probabilities of displacements exceeding certain thresholds. These relationships are developed for DPM1 (derived from one pre-event pair and one co-event pair of SAR images) and DPM2 (derived from multiple pre-event and co-event pairs of SAR images). We show that both DPM types perform similarly well for distinguishing between no surface displacement and some surface displacement. The predictive power of I DPM metrics, as measured by a dispersion term in the fragility model, shows the best performance for low surface fault displacements and DPM2-based indices. Recall and precision performance metrics show favorable performance of fragility models for identifying locations of fault displacement but increasing rates of false positives as fault displacement increases (i.e. predictions of displacements exceeding a threshold that did not occur). While this validation study was performed for a single earthquake sequence involving a specific area of California, these results demonstrate both the capabilities and limitations of I DPM as a rapid, post-event predictive tool for identifying locations and severity of ground displacements in environments similar to those in the Ridgecrest area (flat terrain, limited vegetation).

The OpenQuake Engine started being developed in 2010 and was publicly introduced in 2014 as an open-source software for seismic hazard and risk modeling, aiming to provide a transparent, flexible, and globally accessible platform to the earthquake engineering and hazard science communities. Over the subsequent decade, extensive advancements have significantly expanded its capabilities and enhanced its adoption worldwide. This article comprehensively reviews these developments, detailing the new computational workflows and features implemented in the OpenQuake Engine with an emphasis on the risk component, improvements in its computational efficiency and scalability, and its growing global application across diverse geographical and thematic contexts. Major improvements to the OpenQuake Engine include the earthquake-triggered landslide and liquefaction modules, the infrastructure risk and network connectivity analysis module, the post-event loss amplification module, the financial loss module for insured and reinsured loss calculations, the classical and event-based probabilistic damage calculators, and the site-amplification module. Additional features include the option to condition ground motion fields on station data in scenario calculations, ability to connect ShakeMap outputs to the OpenQuake Engine’s damage and loss calculators, the conditional spectra calculator, vector-valued PSHA, and extension of the risk calculators to volcanic hazards. Performance improvements and enhancements in documentation have been pivotal in strengthening the software’s usability across a variety of computational platforms and user groups. A core contribution of this article lies in compiling and synthesizing over a hundred studies conducted using the OpenQuake Engine, thereby illustrating its versatile application at national, regional, urban, and site-specific scales. Moreover, examples of its use in earthquake insurance pricing and parametric catastrophe bond design are highlighted, demonstrating its practical relevance to risk management and financial resilience. Reflections on lessons learned regarding the importance of open-source practices, robust documentation, sustained user engagement, and interdisciplinary collaboration are discussed to inform future development and maintenance of scientific software with global applications.

This article discusses different approaches to evaluate liquefaction exposure across road networks and inform decision-making processes regarding asset management, emergency preparation and response planning. Using the New Zealand State Highway network, liquefaction exposure is assessed based on ground shaking from two sources: (1) various return period shaking intensities from the National Seismic Hazard Model and (2) a suite of specific earthquake scenarios. The first approach considers the likelihood of liquefaction exposure at each location conditional on different levels of ground shaking, suitable for assessing individual network components. The second approach presents liquefaction exposure for a specific earthquake scenario, capturing the extent of exposure across a network. In addition, it offers a new indicator, the number of events (NoE), identifying network sections that could be affected by liquefaction manifestation across multiple earthquake scenarios. For both approaches, the extent of potential exposure (number of affected 100 m-segments) and the level of network disruption (number of affected links representing segments between intersections) are estimated at both national and regional scales. While the national-scale assessment helps to quantify liquefaction exposure across the entire network, providing valuable insight for asset management, the regional-scale assessments identify potential worst-case scenarios, identify locations affected by multiple events and allow for more informed emergency management decision-making. Future research should expand the multi-scenario approach, incorporate network related aspects, such as criticality or redundancy, and consider recurrence intervals for scenario weighting or perform a full probabilistic liquefaction hazard analysis to enhance the evaluation of potential impacts and to further support decision-making.

Timely and accurate assessments of building damage are crucial for effective response and recovery in the aftermath of earthquakes. Conventional preliminary damage assessments (PDA) often rely on manual door-to-door inspections, which not only are time-consuming but also pose significant safety risks. To safely expedite the PDA process, researchers have studied the applicability of satellite imagery processed with heuristic and machine learning approaches. These approaches output binary or, more recently, multiclass damage states at the scale of a block or a single building. However, the current performance of such approaches limits practical applicability. To address this limitation, we introduce a metadata-enriched, transformer-based framework that combines high-resolution post-earthquake satellite imagery with building-specific metadata relevant to the seismic performance of the structure. Our model achieves state-of-the-art performance in multiclass post-earthquake damage identification for buildings from the Mw 7.8 Türkiye-Syria earthquake on February 6, 2023. Specifically, we demonstrate that incorporating metadata, such as seismic intensity indicators, soil properties, and synthetic aperture radar (SAR) damage proxy maps, not only enhances the model’s accuracy and ability to distinguish between damage classes but also improves its generalizability across different regions affected by an earthquake event. Furthermore, we conduct a detailed, class-wise analysis of feature importance to understand the model’s decision-making across different levels of building damage. This analysis reveals how individual metadata features uniquely contribute to predictions for each damage class. By leveraging both satellite imagery and metadata, our proposed framework enables faster and more accurate damage assessments for precise, multiclass, building-level evaluations that can improve disaster response and accelerate recovery efforts for affected communities.

This study presents a methodology to optimize the analytical derivation of seismic fragility curves of structures located at a given site. Hazard-consistent ground motions in a Multiple Stripe Analysis (MSA) framework are used for this task. The approach aims to reduce the high computational cost typically associated with conducting numerous nonlinear dynamic analyses especially on complex structural models, without compromising the accuracy of the results. The process begins by initializing the fragility parameters’ values from simplified analyses, which are then iteratively updated through a Bayesian approach that incorporates Markov Chain Monte Carlo and Metropolis–Hasting sampling, thereby drastically reducing the number of required analyses. Validation on both SDOF and MDOF structures across various damage states demonstrated convergence to benchmark results within a few iterations. An automated stopping criterion, based on prior and posterior comparison of the fragility parameters’ values, enhances the efficiency of the method. Sensitivity analysis shows that a smaller number of stripes each with fewer records than those utilized in conventional methods can yield stable results, significantly reducing computational demands. In addition, a user-friendly Python tool is provided to facilitate both the reproducibility of the presented results and the application of the proposed method to real-life cases.

Current regional seismic risk assessment methods do not take into account either ground motion directionality or building orientation. A recent study examined the combined effect of ground motion directionality and building orientation for a testbed of imaginary buildings with the same height, structural material, lateral resisting system, and underlain soil properties. That study concluded that future urban seismic risk analyses should consider the combined effects of ground motion directionality and building orientation, and indicated that further research was warranted to conduct this type of assessment in real-world conditions. This investigation specifically examines the combined effects of ground motion directionality and urban layout on the seismic responses and damages of 150 tall buildings in San Francisco’s Financial District during the 1989 Loma Prieta earthquake, using an advanced probabilistic regional seismic risk framework previously developed by the authors. Building responses and damages were computed for three scenarios: (1) buildings in their current orientations, (2) buildings rotated so that one principal axis is aligned with the RotD100 orientation during the Loma Prieta earthquake in downtown San Francisco, and (3) buildings rotated so that both building principal axes are 45° from the RotD100 orientation. The results indicate that peak building responses and damages can vary by up to 30% and 100%, respectively, depending on changes in the urban grid layout. However, responses and damages at individual building stories can change by much more than 30% and 100%, respectively. Larger responses and damages are expected to occur when the city has an orthogonal grid layout and the orientation of RotD100 aligns with the city’s street grid. These findings, which highlight the combined impact of urban layout and ground motion directionality on building responses and damages, have important implications for city officials, planners, insurers, reinsurers, and other stakeholders involved in regional seismic risk assessments.

Recent developments in engineering design have resulted in substantial improvements to the seismic performance of new buildings. However, buildings constructed before recent upgrades to the seismic regulations comprise a large portion of the existing building inventory. Buildings with insufficient seismic capacity are susceptible to extensive damage or collapse during an earthquake, contributing to economic losses and casualties. Effective risk mitigation strategies such as seismic retrofitting could potentially address the vulnerability of the existing building stock to earthquake hazards. Yet, seismic retrofit programs suffer from low take-up rates. Thus, identifying barriers for seismic retrofit adoption and strategies to increase take-up rates can help mitigate losses from future events. This study develops an agent-based model to assess homeowner response to multiple seismic retrofit promotion strategies. The simulation framework is applied to a case study of owner-occupied, residential-detached dwellings in Vancouver, British Columbia, Canada, to evaluate the effectiveness of various potential seismic retrofit promotion strategies. These strategies are compared regarding the number of adopters and the reduction in total annual losses to residential building structures and contents in the City of Vancouver. The main barriers to adopting retrofit measures among different income groups are identified, and appropriate interventions to target those barriers are suggested. Modeling the impact of policies allows policymakers to evaluate their effects and fine-tune the policy interventions before their implementation.

Recent earthquakes have highlighted the seismic vulnerability of existing masonry buildings, pointing out the urgent need to design high-performance and non-invasive strengthening interventions. To this aim, reliable numerical models and assessment procedures are necessary to evaluate their effectiveness and quantify the effects on the structural seismic performance of the building. In this context, the article describes a procedure for the seismic assessment of existing masonry buildings and the design of retrofitting strategies. The procedure is based on a suitable nonlinear numerical model and consists of three phases. In the first phase, the numerical model is defined. In the second phase, the seismic assessment of the building in the as-built configuration is performed, and the required strengthening interventions are designed using nonlinear static analyses. In the third phase, the actual effects of the proposed interventions are evaluated through nonlinear dynamic analyses and the derivation of fragility curves. To test its reliability, the article describes the application of the procedure to two case studies representative of ordinary unreinforced masonry buildings placed in Italy and considered both in the as-built and retrofitted configurations. Their seismic performance was assessed through several nonlinear dynamic analyses performed according to the multiple-stripe approach and employing an equivalent frame modeling strategy. Different strengthening techniques were investigated, designed to conform with the Italian Technical Code, and modulated to achieve a safety index higher than 1 or 0.8 (allowed by the code for existing buildings) as a function of two different site categories (stiff and soft soils). The resulting fragility curves were used to quantify the improvement of the seismic performance guaranteed by the different strengthening strategies and compare their effectiveness concerning two performance conditions (namely usability-preventing damage and global collapse limit states) to identify the best solution for the two considered site categories.

Historical minarets are generally vulnerable to earthquakes because of their poor-quality materials and high slenderness. The objective of this work is to utilize the methodology employed for seismic fragility curves to analyze historical brick minarets, specifically focusing on a specific instance minaret. For this, the minaret of the Hocaalizade Mosque, built in Bursa during the Early Ottoman Period, was chosen. Using the software Abaqus v6.13, the minaret’s finite element model was constructed utilizing shell elements for the minaret and the walls of the mosque, and wire elements for the stair. The model was updated in accordance with the operational modal analysis (OMA) that was carried out in the field. Subsequently, IDA curves were generated for the minaret using Nonlinear Incremental Dynamic Analysis, utilizing 11 actual ground motion records with two horizontal components. A probabilistic approach was utilized in order to acquire the fragility curves for each performance level, which included limited damage, controlled damage, and collapse prevention. The outcomes of nonlinear time history analyze indicate that the minaret sustains damage mostly in two areas: between the transition and shaft, and/or between the balcony and the upper part. The analyses yielded fragility curves using two intensity measures as spectral acceleration and peak ground acceleration. The statistical assessment and regression analyses between each intensity measure and the probability of exceedance indicate that both intensity measures can be considered appropriate for the studied minaret. This minaret experiences the collapse prevention limit when the spectral acceleration (peak ground acceleration) exceed ∼0.27g (0.13g), respectively, with a ∼50% likelihood.

This article presents a numerical investigation into the influence of vertical ground motion on the global seismic response of unreinforced brick-masonry buildings. Vertical accelerations of significant intensity can cause variations in gravity-induced loads, affecting the in-plane lateral capacity of masonry piers. This study employs a suite of numerical structural models to explore the damage potential of vertical accelerations on a masonry building through earthquake simulations. The building features piers with varying aspect ratios, axial loads, and shear resistance. The models are developed using the equivalent-frame modeling approach and nonlinear macroelement within the TREMURI software. Initially, the study demonstrates the capability of the numerical models to replicate dynamic responses under combined horizontal and vertical seismic inputs. The predictive accuracy is validated through simulations of multidirectional shake-table tests on full-scale structures under near-source ground motions. Subsequently, the validated models undergo cloud analysis using unscaled three-component ground motions from earthquakes with moment magnitudes 5–7 and short epicentral distances (below 30 km). The findings indicate that vertical accelerations do not cause considerable differences in global seismic behavior. Any effect on maximum displacement demands for walls with varying geometric and mechanical properties appears random and negligible. Vertical accelerations may only become relevant under certain synchronization scenarios between horizontal and vertical motions, which are rarely encountered in natural settings. This study underscores the importance of considering vertical earthquake motion in seismic analysis yet highlights its generally limited effects on regular masonry structures.

Unreinforced masonry (URM) structures are widely used in informal housing across Colombia, and they represent a significant portion of the country’s building stock. Despite their affordability and accessibility, these structures exhibit high-seismic vulnerability, underscoring the need for detailed risk assessment and mitigation strategies. This study presents the development of fragility and vulnerability functions tailored to the Colombian context, based on a comprehensive database of over 400 URM and semi-confined masonry (CM) buildings from diverse regions. The data set captures variations in story count, wall density, and masonry unit types, enabling the identification of regional construction trends. Advanced three-dimensional macro-element analyses were used in this study, allowing for a modeling approach that accounts for nonlinear effects and coupled failure modes while ensuring computational efficiency. The results from the analyses were found to favorably compare with previous studies, validating the applicability of the developed fragility and vulnerability curves to URM buildings in Colombia and highlighting improvements in the estimation of expected damage and losses. Notably, the curves are consistent with observed damage patterns from the 1999 Armenia and 2008 Quetame earthquakes, reinforcing their validity for seismic risk assessment in Colombian URM buildings. These findings contribute to the development of a robust framework for regional seismic risk assessment, supporting ongoing efforts to reduce disaster risks and improve the resilience of the built environment in Colombia.

Confined masonry (CM) houses are widely used in low- and mid-rise houses worldwide, especially in countries with emerging economies. CM emerged in Latin America as a response to the severe damage observed in unreinforced masonry buildings following significant earthquakes in the early twentieth century. In Colombia, CM construction dates back to the 1930s, with houses up to five stories tall. A key challenge in seismic risk estimation is predicting the behavior of prevalent construction typologies in a region to inform risk mitigation and management strategies. As a part of a larger project called the National Seismic Risk Model for Colombia, this study presents a seismic fragility assessment of CM houses, evaluating the effects of masonry strength, masonry unit type, wall density, construction quality, and number of stories. A total of 72 archetype houses, representative of Colombian CM structures, were analyzed across low, intermediate, and high seismicity zones. Nonlinear models were proposed and calibrated using quasi-static cyclic tests on confined masonry walls and shaking table tests on scaled buildings. For each archetype, nonlinear time history analyses were conducted in OpenSees, using approximately 370 hazard-consistent ground-motion records to represent the hazard at each site of interest. The results from these structural analyses are then combined with damage information to obtain fragility curves for this building typology. The fragility results of this study, combined with vulnerability functions, will serve as inputs to calculate risk metrics later on as part of the National Seismic Risk Model for Colombia. The present work provides a region-specific fragility assessment, calibrated with local experimental data, which enhances its applicability within Colombia and potentially to other Latin American countries with similar construction practices and standards. These findings can contribute directly to national seismic risk mitigation initiatives.

To reduce disaster impacts, initiatives have been promoted to assess seismic risk in developing countries like Colombia. To achieve this, it is crucial to develop exposure models that consolidate parameters of assets that may be affected by a seismic event, including their geographic location, material, structural system, and economic value. This last parameter is often assessed by using the asset replacement cost. Replacement cost valuations are often based on rough estimates that overlook factors like demolition, material transport, land suitability, structural typology, and regional socioeconomic dynamics. This study focuses on developing a simplified national replacement cost model for residential buildings in Colombia, a country that exemplifies the complexities and unique characteristics among developing nations. Colombia’s diverse seismicity, topography, socioeconomic disparities, and varied climatic conditions present an ideal case for examining how a streamlined approach for cost estimation can be implemented and effectively used. Within the framework of the open National Seismic Risk Model (MNRS), the proposed methodology includes over 50 representative combinations of materials and structural systems obtained from the available exposure models of the country. The model integrates traditional construction costs of common building types with variables reflecting current socioeconomic conditions and regional transportation dynamics. The research highlights the importance of including indirect costs and transportation dynamics for accurate nationwide replacement costs. The regional models, calibrated to reflect local socioeconomic and logistical dynamics, demonstrate a range of fit that varies significantly across regions. This variability highlights the importance of calculating replacement costs using a regional approach rather than assuming a homogeneous national model. The study also shows that reinforced concrete systems, especially moment-resisting frames, are costlier than masonry-based systems. The model updates Colombia’s exposure models in the MNRS, providing a crucial tool for decision-makers in a seismically active country.

This article introduces V-FAST, an open-source computational platform designed to support the implementation of performance-based earthquake engineering (PBEE). V-FAST enables the estimation of fragility functions for individual buildings and representative taxonomies and the calculation of vulnerability functions using a story-based methodology. This story-based loss estimation (SBLE) approach leverages structural response data and component-level damage models to compute expected losses at the component, story, and building levels. The platform integrates key components of the Pacific Earthquake Engineering Research (PEER)-PBEE framework into a streamlined workflow that enhances interpretability and facilitates its application across research, academic, and professional settings. V-FAST features a graphical interface that provides full visualization of inputs, intermediate computations, and final outputs, thereby improving usability and transparency. While initially developed to support national risk modeling efforts in Colombia, its structure and flexibility make it broadly applicable for detailed seismic risk assessments in diverse contexts.

A city’s capacity to withstand and recover from seismic events plays a crucial role in safeguarding the well-being of its residents. While numerous studies have investigated the recovery cost and time of buildings following earthquakes, the effects of soil and foundation have often been overlooked despite their known influence on seismic performance. This study addresses this gap by examining the possibility of optimizing the foundation size for low-rise concentrically braced frame (CBF) buildings, considering repair cost and recovery time as key performance indicators. For this purpose, one-, two-, and three-story steel buildings located in Vancouver, Canada, with X-bracing systems, are designed for two typical site classes, one representing stiff soil conditions near the site class C/D boundary, and the other soft soil conditions near the site class D/E boundary. Monte Carlo simulation is employed to incorporate uncertainties in the material properties, gravity loads, seismic demand, and the inherent damping of the structure. Nonlinear response history analyses are conducted at the design-level intensity using OpenSees. The foundation size, including footings that satisfy US design requirements as well as Canadian capacity-protected (CP) and not capacity-protected (NCP) options, is treated as the decision variable. The results indicate that the footing size significantly influences the seismic response mode of low-rise buildings, with peak floor acceleration emerging as the most influential engineering demand parameter affecting both repair cost and recovery time. The findings suggest that while the footing size has a negligible impact on the functional recovery time of buildings on soft soil, larger footings on stiff soil may result in extended recovery times. Although the performance difference between footing sizes is often small, the increase in cost for larger footings can be significant. Therefore, this study indicates that NCP footings (i.e. rocking foundations) may be the more advantageous choice for short-period CBF buildings.

This study investigates the impact of system effects on the dynamic behavior of light frame timber buildings (LFTBs) through shake table tests and numerical analysis. Here, the term “system effects” encompasses the influence of the transverse shear walls, the out-of-plane bending stiffness of the diaphragms, and the gravity load, particularly in LFTBs with non-planar shear walls. The findings of this research reveal that system effects notably reduce story drift demands and enhance the lateral stiffness and damping ratio of LFTBs with respect to results from numerical models that do not consider component interactions. This observation highlights a discrepancy between the actual lateral stiffness and that predicted by existing models, particularly at relatively small levels of story drift. The underestimation of these engineering parameters is more apparent at the lower stories, underscoring the significant role of the gravity load in amplifying the beneficial effects of the transverse shear walls and the out-of-plane bending stiffness of the diaphragms. These insights are vital to refine the seismic design and analysis of LFTBs and underscore the importance of incorporating system effects into both numerical and analytical models. This enhanced understanding of component interactions in LFTBs sets the stage for increasing adoption of LFTBs as a sustainable and resilient building solution in earthquake-prone areas.

The 2019 Mw 6.1 Central Luzon earthquake generated significant long-period ground motions in Metro Manila, the Philippines, affecting high-rise buildings with non-structural damage on rooftop water storage facilities. Due to the unavailability of direct instrumental measurements, this study employed video data analysis to estimate the response of the affected buildings during the earthquake. The natural periods of four analyzed buildings were estimated in the range of 3.3–5.2 seconds, corresponding to the period range (3–6 seconds) of the observed ground motions with high spectral amplitudes in the area. The time-variant features of the ground motion records revealed the dominant influence of surface waves at periods exceeding 3 seconds. While the estimated acceleration and displacement response levels were relatively small in the period range of the affected buildings, the prolonged duration of surface waves sustained the liquid sloshing oscillations inside the water tanks and suggested to lead the observed non-structural damage. These findings suggest that large-scale structures with natural periods in the 3- to 6-second range, typically corresponding to 30–60 story buildings, may be particularly susceptible to resonance effects during large earthquakes and at risk of prolonged shaking with sloshing effects and nonstructural damage even during moderate earthquakes in this region. By using video data as an alternative data source, this study provides the first assessment of high-rise building response to long-period motions in Metro Manila, bridging a knowledge gap in a region with limited availability of data from building instrumentation. Further investigations and potential updates to local seismic provisions are suggested to address the effects of long-period surface waves on high-rise buildings in Metro Manila.

Following the 2011 downtown Christchurch earthquake, 60% of buildings in Christchurch were demolished and reconstructed. Such practices are costly in terms of money and carbon emissions. Structures need to be proportioned so that they can be reused after one or several ground motions. To do so, it is important to understand the effect of previous shaking on drift demands. Past studies conducted to investigate the effect of previous shaking were based almost exclusively on numerical analyses that used a limited set of parameters. Conclusions from past numerical analyses do not lead to a clear consensus, and results from past studies have not been systematically vetted against measurements from structures tested in the laboratory or evidence from the field. To address these issues, the plausible effects of previous shaking on drift demands were re-evaluated using (1) numerical analyses of Single and Multi-Degree-of-Freedom oscillators with an expanded set of parameters and (2) measurements from 220 experimental tests of structures subjected to repeated simulated base motions. The compiled evidence supports at least two conclusions: (1) Repeats of medium or high-intensity motions strong enough to cause yielding in their first occurrence are unlikely to produce large relative increases in peak drift demands in structures with stable force–displacement relationships not susceptible to brittle failures. This phenomenon was observed in repeated motions not preceded by more intense motions, as well as in repeated motions preceded by more intense motions. The latter observation had not been reported in the literature to date. (2) Increases in peak drift demands were observed to be likely to occur if the first motion (in a sequence of motions containing a pair of repeated motions) is mild enough not to cause cracking and/or yielding, but the second instance of the same motion is preceded by larger intensity motions causing cracking and/or yielding.

Estimating the drift capacity (DC) of reinforced concrete (RC) structural walls is crucial to assess seismic performance of buildings in earthquake-prone regions. Numerous investigations have been conducted on the subject. Nevertheless, most of these investigations focus on walls without prior damage and a single expected earthquake. Recent tests conducted on RC walls suggest that displacement history does not affect DC, if the maximum amplitude of previous cycles is smaller than a threshold, regardless of the number of applied cycles. How to define such threshold and how prior cycles with amplitudes exceeding it affect DC remains unclear. This study assessed the effect of cyclic displacement history—or displacement cycles—on the DC of RC structural walls, using a statistical analysis. Results indicate that DC decreases as the intensity of cyclic displacement history increases. Nevertheless, this decrease is considerably smaller than differences between measured values of DC and estimates obtained using available empirical formulations and a calibrated machine learning algorithm.

This article assesses the seismic design provisions for floor diaphragms per ASCE/SEI 7-22 Section 12.10.1 and Section 12.10.3, with emphasis on how these provisions account for the higher-mode effects on peak horizontal floor accelerations of earthquake-resistant buildings. A framework is developed for processing and analyzing strong-motion acceleration data from buildings monitored by the California Strong Motion Instrumentation Program (CSMIP), which is used to assess the floor diaphragm design acceleration coefficients in ASCE/SEI 7-22. These coefficients, which estimate peak floor accelerations at the design-level earthquake, are modified in this study to consider the intensity of measured ground motions and the level of earthquake-induced inelastic building response. First, the spectral response factors, defined as the ratio between the spectral response acceleration at a given floor and that at the ground, are evaluated at the second- and third-mode periods and compared with those at the first-mode period to assess the higher-mode effects. Then, two metrics are defined to compare the modified acceleration coefficients with the measured peak floor accelerations. The results confirm the need to consider the characteristic dynamics of the buildings to estimate the design forces for floor diaphragms. This consideration is included in ASCE/SEI 7-22 Section 12.10.3 but not rationally considered in Section 12.10.1. The modified acceleration coefficients based on ASCE/SEI 7-22 Section 12.10.1 can considerably underestimate the peak floor accelerations, whereas those based on Section 12.10.3 can capture the increased peak floor accelerations caused by the higher-mode earthquake-induced inertial forces. Thus, the authors recommend using ASCE/SEI 7-22 Section 12.10.3 over Section 12.10.1 to estimate the design forces for floor diaphragms; however, certain assumptions considered in Section 12.10.3 require further revision.

Seismic loss estimation is an essential tool for assessing the performance and resilience of buildings exposed to seismic hazards. Numerous loss methodologies with varying fidelities exist, with each comprising different steps and requiring analysts to adopt certain modeling decisions and assumptions. This study compares three seismic loss estimation methods, namely FEMA P-58 component-, story loss function (SLF)-, and HAZUS assembly-based approaches, using a database of 621 steel special moment-resisting frame buildings with diverse designs and geometries. In addition, a set of sensitivity analyses are performed to evaluate the influence of key modeling decisions in fragility and loss assessment stages on different loss methodologies. These decisions include (1) intensity measure-engineering demand parameter (IM-EDP) formulation to derive fragility functions, (2) EDP proxy for fragility models within the assembly-based method, (3) characterization of demolition fragility, and (4) uncertainties in nonstructural component quantities. The results show that the assembly-based approach estimates lower median loss for short- to medium-rise buildings but higher estimates for taller ones, with significantly higher variability in losses for multi-story buildings compared to the component-based approach. In contrast, the SLF-based method yields slightly higher median loss for 1-story buildings but consistently lower estimates for multi-story buildings than the component-based approach. The sensitivity analysis highlights that the critical modeling decisions vary by the selected method. The assembly-based approach shows greater sensitivity to the choice of EDP proxy impacting the dispersion of losses. In contrast, uncertainties in nonstructural component quantities predominantly govern both the median and dispersion of losses for the component-based approach, and the selected IM-EDP formulation has the highest effect on SLF-based estimates.

The M_w5.9 Jishishan earthquake, China, is a thrust-type event that occurred on 18 December 2023, causing extensive damage to buildings and geological features in the epicentral area. Post-earthquake damage surveys and historical earthquake data indicate that thrust faulting and sedimentary effect are key contributors to the observed damage patterns. To assess how these factors influence ground motion, broadband simulations are conducted within the 0–5 Hz frequency range, employing a physics-based deterministic approach to model earthquake rupture and wave propagation. The numerical model is first validated by comparing data from 20 well-recorded stations during the Jishishan earthquake. Subsequently, three different models (Topography, Flat, and Bedrock) were constructed to assess the impact of thrust fault and sediment on ground motion. The results show that the ground motion on the hanging wall is much higher than that on the footwall, demonstrating a pronounced hanging wall-footwall effect, with a maximum hanging wall-to-footwall ratio of 3.62. Furthermore, the simulated ground motions with and without sedimentary structures indicate that sediment tends to focus the seismic wavefield, resulting in amplification and prolongation of the ground motion, with peak ground motion and duration amplifications reaching 2.57 and 2.15 times, respectively. These findings suggest that the coupling effect of thrust fault and sedimentary structure dictates the ground motion distribution of the Jishishan earthquake. The identified hanging wall-footwall effect and sedimentary amplification provide a reasonable explanation for regional ground motion anomalies.

Proper incorporation of shallow site effects in hybrid broadband ground-motion simulation is essential to improving predictions at soil sites. This paper validates and compares four methods to account for these effects in the predominantly linear regime, using 1446 ground motions from 213 small-magnitude earthquakes ( 3 . 5 ≤ M W ≤ 5 . 0 ) recorded at 38 sites in New Zealand representative of a wide range of soil conditions. These methods require V S 30 or a shear-wave velocity profile, with the second approach relying on either the square-root-impedance method or the theoretical one-dimensional (SH1D) transfer function. Incorporating shallow site effects with any of the considered methods significantly improves accuracy and precision for several intensity measures, including pseudo-spectral acceleration at short vibration periods. Although the reduction in prediction variability was comparable between methods, the SH1D-based approach showed particular benefits in the case of (1) stiff sites for which the simulation overestimates attenuation effects; (2) relatively stiff sites with high-frequency resonances; (3) relatively soft sites with strong resonances in the intermediate frequency range; and (4) sites with a near-surface predominant frequency lower than the frequency range considered for the application of the V S 30 -based adjustment. This study shows that the potential prediction improvements obtained by using more advanced site-adjustment methods that incorporate additional site-characterization data are highly dependent on the site characteristics and the quality of the ground-motion simulation in a given region. These findings can help to inform site response method selection in forward applications.

The 2023 Kahramanmaraş earthquake sequence significantly impacted southeastern Türkiye. A comprehensive field investigation of 40 cone penetration tests and 7 seismic cone penetration tests was conducted to characterize the subsurface conditions of several areas affected by liquefaction in the port city of İskenderun. The investigations were performed at a key seismic station in the area, five areas with differing liquefaction-induced building settlements, and three lateral spread sites. The reclaimed shoreline area, which exhibited the most significant liquefaction effects, is underlain by thick medium dense clean sand deposits. Ground shaking characteristics in the investigated areas are estimated and essential subsurface data for developing high-quality field case histories are developed to support studies of liquefaction triggering and effects in İskenderun. In this context, it contributes to advancing liquefaction engineering and informs seismic hazard mitigation strategies in urban areas.

We investigate the influence of earthquake source characteristics and geological site parameters on fault scarp morphologies for thrust and reverse fault earthquakes using geomechanical models. A total of 3434 distinct element method (DEM) model experiments were performed to evaluate the impact of the sediment depth, density, homogeneous and heterogeneous sediment strengths, fault dip, and the thickness of unruptured sediment above the fault tip on the resultant coseismic ground surface deformation for a thrust or reverse fault earthquake. A machine learning model based on computer vision (CV) was applied to obtain measurements of ground surface deformation characteristics (scarp height, uplift, deformation zone width, and scarp dip) from a total of 346,834 DEM model stages taken every 0.05 m of slip. The DEM dataset exhibits a broad range of scarp behaviors, generating monoclinal, pressure ridge, and simple scarps—each of which can be modified by hanging wall collapse. The parameters that had the most influence on surface rupture patterns are fault displacement, fault dip, sediment depth, and sediment strength. The DEM results comprehensively describe the range of historic surface rupture observations in the Fault Displacement Hazards Initiative (FDHI) dataset with improved relationships obtained by incorporating additional information about the earthquake size, fault geometry, and surface deformation style. We suggest that this DEM dataset can be used to supplement field data and help forecast patterns of ground surface deformation in future earthquakes given specific anticipated source and site characteristics.

Ground motion models (GMMs) are typically developed for 5% damped elastic response spectra. However, in practice, structural and non-structural engineered facilities require a range of damping ratios for seismic design, analysis, and hazard assessment. To address this need, damping scaling factor (DSF) models were developed using Bayesian inference with integrated nested Laplace approximation (INLA) for pseudo-acceleration spectra (or displacement spectra) and absolute acceleration spectra derived from subduction earthquakes in offshore (S-net) and onshore (K-NET and KiK-net) regions of Japan. The S-net stations are categorized into buried and unburied stations based on factors such as seawater depth and arrangement form. The proposed DSF model incorporated moment magnitude, rupture distance, damping ratio, and station type as predictor variables, employing a linear function of ln(β) to differentiate between onshore, offshore buried, and offshore unburied ground motions. The DSF model is applicable to subduction earthquake scenarios with moment magnitudes ranging from 5.5 to 9.1, rupture distances up to 1000 km, and 11 damping ratios between 0.5% and 30% for spectral periods of 0.01 to 10 s. It reflects significant differences among onshore, buried and unburied ground motions across most spectral periods at various damping ratios, particularly at low damping ratios and long periods. In addition, standard deviation models were developed for the proposed DSF models using a cubic function of ln(β/5). Compared to the observed standard deviation, the proposed model effectively captures the observed trends. The proposed DSF model can be effectively used to scale onshore and offshore 5% damped GMMs to other GMMs with damping ratios ranging from 0.5% to 30% for subduction earthquakes, providing a valuable tool for probabilistic seismic hazard assessment and engineering applications.

Physics-based simulation of subduction earthquake ground motions remains less comprehensively validated than for shallow crustal earthquakes, despite subduction events contributing significantly to global seismic hazard. In this study, subduction-specific simulation models were developed and validated for small-magnitude ( M w 3.5–5) interface and slab earthquakes using hybrid broadband ground-motion simulation. Simulation models were constrained by (1) global empirical ground-motion models, (2) a global database of finite-fault rupture models, and (3) global ground-motion simulation studies. The simulation models include subduction source-specific representations for stress parameter and rupture velocity, with a significant depth dependence of the stress parameter for slab earthquakes. Volcanic backarc effects on anelastic path attenuation are also included through path attenuation-based scaling of the rock quality factors in the simulations. The simulations leverage models for site and basin effects which have been validated using crustal earthquakes, for which there are many recorded ground motions, and the subduction-specific model modification mainly affect the high-frequency component of the ground-motion simulations above 1Hz. Simulation predictions were validated against a compiled dataset of observed subduction earthquake ground-motion records in New Zealand. The subduction-specific modifications significantly improve predictive performance compared to the use of simulation parameter values for active shallow crustal earthquakes and provide comparable accuracy to prior simulations for crustal earthquakes in New Zealand. Despite these promising results, further studies are needed to address prediction residuals at low frequencies (f ≤ 1 Hz), as well as extending validation to larger magnitude earthquakes.

Simulating ground motion (GM) is essential for assessing seismic hazards and evaluating the risks to civil infrastructure in earthquake engineering. The widely used stochastic method achieves temporal nonstationarity in simulated GM by applying a window function to Gaussian white noise. Typically, this window function has a fixed shape due to its constant shape parameters, resulting in uniform waveforms in simulated GMs. This study proposes a novel approach that generates a window function from recorded GMs, rather than one constrained by a specific mathematical form with constant parameters. Here, the relative location of the peak ground acceleration (P) and the 5%–75% significant duration (D₇₀) are selected as shape parameters for the window function. To determine target shape parameters for specific scenarios, this study establishes a probability distribution model for P and applies a well-established predicting model for D₇₀. A time series, shaped to meet the target parameters, is generated from recorded GMs, and its normalized envelope, computed using the Hilbert transform, is utilized as the window function. The proposed approach enables the window function’s shape parameters to better align with statistical characteristics, incorporating the temporal nonstationarity of recorded GMs into the simulation. Case studies on the M_w 6.9, 2008 Iwate and M_w 6.8, 2007 Chuetsu-oki earthquakes illustrate improvements in the envelopes and durations of the simulated GMs.

The 18 March 2020 M 5.6 Magna, Utah earthquake near Salt Lake City was recorded by more than 160 strong motion/broadband stations. The ground motions compare favorably with the NGA-West2 ground motion models (GMMs) using estimates of V_S30 but there are numerous exceptions. The purpose of this study was to evaluate the site effects at 26 seismic stations located in the Salt Lake Valley. We evaluated the data from the mainshock and seven largest aftershocks (M 3.9 to 4.6) and performed a one-dimensional (1D) random vibration theory equivalent-linear site response analysis (SRA). We compared our predicted site amplification with the recorded ground motions to evaluate which features in the data could be predicted using a 1D approach. We first updated the 2008 Utah Geological Survey shallow shear-wave velocity (V_S) database. Shallow V_S profiles were assigned to each seismic station and extended to the source depth of 7 km using the Wasatch Front Community Velocity Model. Next an inversion was performed to evaluate stress drops, kappa, and Q(f) using recordings from 109 earthquakes (M 2.9 to 5.6). The resulting parameters were then used in the SRA for four Salt Lake Valley site categories to compute linear amplification factors (AFs). These factors were then compared with the AFs (response spectra) implied by the NGA-West2 GMMs for the 26 seismic stations. Horizontal-to-vertical spectral ratios were also calculated from the recorded data and compared with the AFs (Fourier amplitude spectra) from the SRA to evaluate the consistency of the predicted site resonant frequencies. Our predicted AFs for the mainshock generally agree with the NGA-West2 AFs except for the softest unit where we predict more soil nonlinearity and higher long-period amplification. Our results also show an underprediction at short periods and close-in distances which may be due to a source effect, for example, radiation pattern and/or rupture directivity.

In the present study, an accurate ground motion model (GMM) for the Korean Peninsula is developed by considering local seismological characteristics, including source, site, and three-dimensional (3D) path effects. An existing GMM for rock site conditions is adopted as the base model. To enhance the accuracy of this model and incorporate local seismological features, residuals between the observed and predicted intensity measures (IMs), such as peak ground acceleration ( PGA ) and pseudo-spectral acceleration ( PSA ), are computed. These residuals are further disaggregated into components associated with specific seismological characteristics: δ Source , δ Site , and δ Path . Regression analyses are conducted to develop empirical equations for δ Source , δ Site , and δ Path based on the calculated residuals. These correction terms are subsequently integrated into the existing GMM to establish the improved model. A practical example is provided to illustrate the application of the proposed GMM. The accuracy and reliability of the improved model are validated by comparing the observed IM values with those predicted by the proposed GMM.

We present a application programming interface (API)-enabled relational database of global earthquake ground motion intensity measures, associated metadata, and processed time-series data. Raw ground motion records were processed by the authors using either manual or semi-automated processing procedures, and every processed record has passed a quality review by a trained analyst. Computed intensity measures include peak acceleration and velocity, pseudo-spectral acceleration response spectra, cumulative absolute velocity, Arias Intensity, and Fourier amplitude spectra. The processed time-series data, associated metadata, and ground motion intensity measures were organized into a web-served relational database consisting of 32 tables connected by primary/foreign key pairs. Ground motion metadata and intensity measures (but not time-series) from the Next-Generation Attenuation (NGA)-East and NGA-West2 projects and the Hellenic Strong-Motion Database are also contained in the database. As of this writing (June 2025) the database includes intensity measures and metadata for 76,242 multi-component ground motions recorded at 9927 stations for 1391 events, and is approximately 73.5 GB in size. The database is built using the MySQL relational database management system, and is accessible through a web interface and also an API, which allows users to retrieve data using straightforward and intuitive uniform resource locators (URLs). Compared with more traditional file-download-based methods for data release, the relational database (1) increases storage efficiency, (2) improves data integrity, and (3) enables users to query the data subset they wish to retrieve rather than downloading the entire database and loading it into memory. Furthermore, the web-served nature of the database means that users have immediate access to ground motion data following collection, review, and uploading. Periodic static releases of the database will be published as a means of archiving and facilitating reproducibility. The database has been designed to accommodate growth, with ongoing efforts to integrate global ground motion data (e.g. data development for the NGA-West3 project).

Reinforced concrete (RC) structures, widely used in mid- to high-rise construction, face significant challenges related to sustainability, durability, and seismic resilience. Despite extensive experimental research on RC walls, studies specifically focusing on their torsional response remain limited. To address these gaps, the ERIES-ALL4wALL project investigates the torsional and bidirectional flexural behavior of RC U-shaped walls, a key structural feature in contemporary and future high-rise buildings. This article presents experimental findings from shake-table tests on two slender U-shaped walls, evaluating their nonlinear flexural and torsional performance under realistic seismic ground motions. Advanced instrumentation techniques—such as camera-based vibration measurements—are introduced to capture detailed performance data. The accompanying open-access data are then outlined, enabling further research and development of models to improve the resilience and sustainability of RC core walls in urban environments.

This article presents a dataset from an experimental campaign investigating the out-of-plane (OOP) seismic response of unreinforced masonry (URM) gables in existing buildings. Addressing a critical gap in published research, the dataset provides novel experimental data on the incremental dynamic OOP behavior of three URM gables tested under seismic loading until full collapse. All three gables were nominally identical but differed in their interaction with the supporting roof structure. This interaction was experimentally reproduced by imposing differential motions at the top of the gables, which were either linearly amplified or both amplified and phase-shifted relative to the motion at the base. This approach ensured idealized and numerically replicable boundary conditions, making the dataset an ideal benchmark for refining existing and developing new modeling approaches for URM structures. The dataset includes measured and calculated acceleration, displacement, and force time histories. Beyond supporting the validation and development of numerical models, it can also contribute to improving guidelines for the out-of-plane seismic assessment of URM gables and is openly available for further research and engineering applications.