The U.S. Geological Survey (USGS) periodically releases updates to National Seismic Hazard Model (NSHM) for the United States and its territories leveraging current scientific knowledge and methodologies to guide public policy, building codes, and risk assessments regarding potential ground shaking due to earthquakes that may result in infrastructure damage. In subduction zones, there is a need to separate the earthquake catalog into tectonic regimes to create specific seismicity models for which the most appropriate ground-motion models are then applied. Here, we describe newly developed methods and software, called CatSep, that classifies subduction zone events into three primary tectonic regimes: crustal, interface, and intraslab. This method incorporates information about the location of the earthquake relative to the subducting slab, the depth of the Mohorovi & ccaron;i & cacute; discontinuity, and the earthquake's moment tensor. Applying this method is a first step in the NSHM workflow for regions covering U.S. subduction zones. Results using this subduction zone earthquake catalog separation tool for the 2025 Puerto Rico and U.S. Virgin Islands NSHM earthquake catalog are presented and analyzed.

The 29 July 2025 Mw 8.8 Kamchatka, Russia, earthquake was the sixth largest instrumentally recorded earthquake. This event was seismically well observed at regional and teleseismic distances, but publicly available near-source data were sparse at the time of the event, presenting unique challenges for rapid source and impact characterization. The U.S. Geological Survey (USGS) National Earthquake Information Center provides global real-time monitoring for earthquakes, including rapid response information products that estimate source characteristics, shaking, and the resulting impacts. We describe the USGS rapid response earthquake information products following the Kamchatka event and discuss their implications for ongoing hazards in the region. We describe potential improvements to our response workflows motivated by this event, including more rapid constraints on source geometries and the automated selection of fault geometries for finite-fault inversions. The rapid response products together support the interpretation of a unilateral southwestward rupture with significant slip on the southwestern end of the rupture extent. The Mw 8.8–9.0 event in 1952, which ruptured a comparable extent of the Kuril–Kamchatka subduction interface, has many similarities to the 2025 rupture. This illustrates that slip deficits may remain following great earthquakes and highlights the usefulness of comparative studies between historic and modern events.

We present a method to update the geospatial liquefaction model used by the U.S. Geological Survey's near-real-time ground failure product with subsurface geotechnical data. The geospatial model estimates liquefaction probability from peak ground velocity (via ShakeMap) and geospatial susceptibility proxies. In many regions, additional information relevant to constraining liquefaction likelihood is also available, including surface geology maps and subsurface geotechnical measurements. There is currently no mechanism to use these data in the ground failure product liquefaction model, even though these data could provide more precise constraints on spatial variations in the lithologic character of the soil (surface geology) and direct measurements of the subsurface mechanical properties that affect liquefaction occurrence and severity (geotechnical measurements). In this study, we develop a method to integrate these data with the geospatial model and assess how these data can improve regional-scale predictions. We develop a Bayesian updating framework and apply it to the 1989 magnitude 6.9 Loma Prieta, California, earthquake, for which mapped observations are available to evaluate performance. We constrain the Bayesian framework with 373 Northern California cone penetration tests and liquefaction susceptibility classes based on the mapped surface geology. This Bayesian model incorporates geotechnical information into the geospatial model and more accurately predicts liquefaction occurrences than the geospatial model, while sacrificing less accuracy in terms of predicting the absence of liquefaction than the geotechnical model. In future applications, this approach could be adapted to update other geospatial models using locally available subsurface data.

We describe automated ground-motion processing software named gmprocess that has been developed at the U.S. Geological Survey (USGS) in support of near-real-time earthquake hazard products. Because of the open-source development process, this software has benefitted from the involvement and contributions of a broad community and has been used for a wider range of applications than was initially envisioned. Here, we give an overview and introduction to the software, including how it has leveraged other open-source libraries. We highlight some key features that gmprocess provides, compare response spectra calculated with the automated processing approach of gmprocess to the response spectra provided by the Next Generation Attenuation projects, and summarize projects that have utilized gmprocess. These use-cases demonstrate that this software development effort has been successfully leveraged in earthquake research activities both within and outside the USGS.

With the recent successful accounting of basin depth ground-motion adjustments in seismic hazard analyses for select areas of the western United States, we move toward implementing similar adjustments in the Atlantic and Gulf Coastal Plains by constructing a sediment thickness model and evaluating multiple relevant site amplification models for central and eastern United States seismic hazard analyses. We digitize and combine existing sediment thickness data sets into a composite surface that delineates the base of Cretaceous sediments under the Atlantic Coastal Plain and the base of Mesozoic sediments under the Gulf Coastal Plain. Amplification models dependent on sediment thickness, site natural period, and source-to-site path length are compared with data sets of observed ground motions to evaluate the ability of the new models to improve ground motion estimates. We find that the amplification models can account for observed trends in sediment-thickness and period-dependent residuals, but some tuning is required. For example, the model of Chapman and Guo requires a reference V S 30 , the time-averaged shear-wave velocity within 30 m of the Earth’s surface, for non-Coastal Plain sites, which we estimate to be between about 1 and 2 km/s. Along with our sediment thickness model, we estimate a velocity profile for application to the Harmon et al. site-natural-period-based model in order to best match the Chapman and Guo period dependence for a broad range of sediment thicknesses. The Next Generation of Attenuation models for the eastern United States Gulf Coast path-based adjustment models can also account for seismic attenuation in the Coastal Plain sediments and reduce the standard deviation of total residuals. If enacted in the U.S. Geological Survey National Seismic Hazard Model, these amplification models will reduce predicted short-period (<1 s) and increase predicted long-period (>1 s) ground motions in the Coastal Plains appreciably.

The 30 November 2018, magnitude (Mw) 7.1 earthquake in Southcentral Alaska triggered substantial landslides, liquefaction, and ground cracking throughout the region, resulting in widespread geotechnical damage to buildings and infrastructure. Despite a challenging reconnaissance and remote-sensing environment, we constructed a detailed digital inventory of ground failure associated with the event from several sources. Sources included information derived from remotely sensed data, and data compiled from literature, social media postings, and earthquake damage information compiled by local, state, and federal agencies. Each instance of ground failure within the inventory contains information on the location and type of observed ground failure, and the methods and data used to document the occurrence. Where high-quality data, such as LIDAR or satellite imagery, were available and showed the ground-failure instance clearly, the extent is mapped as a polygon or polyline. All other locations are mapped as points. There are a total of 886 ground-failure instances documented within the inventory (400 landslides, 286 liquefaction features, and 200 features unattributed to specific processes). A semi-quantitative confidence scheme is used to describe mapping certainty associated with each ground-failure feature. This inventory represents a relatively moderate ground-failure-triggering event that occurred in a subarctic environment. This data paper describes the content within the inventory, the inventory data collection procedures, and limitations of the data. Events of this type are not often documented in detail; thus, adding the inventory data to the US Geological Survey Open Repository of Earthquake-Triggered Ground-Failure Inventories further diversifies the datasets available to the scientific community to be used to better understand and model earthquake-triggered ground failure.

Model development in the Next Generation Attenuation-East (NGA-East) project included two components developed concurrently and independently: (1) earthquake ground-motion models (GMMs) that predict the median and aleatory variability of various intensity measures conditioned on magnitude and distance, derived for a reference hard-rock site condition with an average shear-wave velocity in the upper 30 m ( VS30) = 3000 m/s; and (2) a site amplification model that modifies intensity measures for softer site conditions. We investigate whether these models, when used in tandem, are compatible with ground-motion recordings in central and eastern North America (CENA) using an expanded version of the NGA-East database that includes new events from November 2011 (end date of NGA-East data curation) to April 2022. Following this expansion, the data set has 187 events, 2096 sites, and 16,272 three-component recordings, although the magnitude range remains limited (∼4 to 5.8). We compute residuals using 17 NGA-East GMMs and three data selection criteria that reflect within-CENA regional variations in ground-motion attributes. Mixed-effects regression of the residuals reveals a persistent pattern in which ground motions are overpredicted at short periods (0.01–0.6 s, including peak ground acceleration (PGA)) and underpredicted at longer periods. These misfits are regionally variable, with the Texas–Oklahoma–Kansas region having larger absolute misfits than other parts of CENA. Two factors potentially influencing these misfits are (1) differences in the site amplification models used to adjust the data to the reference condition during NGA-East GMM development relative to CENA amplification models applied since the 2018 National Seismic Hazard Model (NSHM), and (2) potential bias in simulation-based factors used to adjust ground motions from the hard-rock reference condition to a VS30 = 760 m/s condition. We provide adjustment factors and their epistemic uncertainties and discuss implications for applications.

Archival earthquake studies often focus on event and source characteristics for use in earthquake catalogs, seismotectonic understanding, and ground-motion studies—many of these targeting better constraints for probabilistic seismic-hazard analyses. The ShakeMap Atlas, in contrast, focuses on spatial distribution of shaking for the historical events, providing the best constraints at all locations that experienced significant shaking for each event, facilitating analyses of human experience, damage, and induced hazards (ground failure). The aim of the Atlas is to gain a general understanding and depiction of the shaking distribution for a suite of canonical earthquakes, and, coupled with loss data for each event, to provide a basis for earthquake loss model calibration, among other uses. Although the initial motivation for developing the ShakeMap Atlas was calibrating the U.S. Geological Survey (USGS) Prompt Assessment of Global Earthquakes for Response system, over time, the Atlas has proved to be a useful tool for its users, and, as such, its scope has been vastly expanded in this newest version. The fourth version of the USGS ShakeMap Atlas is an openly available compilation of over 14,000 ShakeMaps of significant global earthquakes between 1900 and 2020. This revision includes: (1) the latest version of the ShakeMap software that provides refined uncertainty estimations and improved methods to combine macroseismic observations with updated ground-motion models; (2) an updated earthquake source catalog; (3) a refined strategy to select suites of prediction and conversion equations based on a new seismotectonic regionalization scheme; and (4) expanded macroseismic intensity and ground-motion datasets. We also tabulate reported economic losses and fatalities for Atlas events where such data are openly available. These changes make the new ShakeMap Atlas a self-consistent, calibrated catalog invaluable for investigating near-source ground motions, as well as seismic hazard, scenario, risk, and loss-model development and testing.

Several rupture directivity models (DMs) have been developed in recent years to describe the near-source spatial variations in ground-motion amplitudes related to propagation of rupture along the fault. We recently organized an effort toward incorporating these directivity effects into the US Geological Survey (USGS) National Seismic Hazard Model (NSHM), by first evaluating the community’s work and potential methods to implement directivity adjustments into probabilistic seismic hazard analysis (PSHA). Guided by this evaluation and comparison among the considered DMs, we selected an approach that can be readily implemented into the USGS hazard software, which provides an azimuthally varying adjustment to the median ground motion and its aleatory variability. This method allows assessment of the impact on hazard levels and provides a platform to test the DM amplification predictions using a generalized coordinate system, necessary for consistent calculation of source-to-site distance terms for complex ruptures. We give examples of the directivity-related impact on hazard, progressing from a simple, hypothetical rupture, to more complex fault systems, composed of multiple rupture segments and sources. The directivity adjustments were constrained to strike–slip faulting, where DMs have good agreement. We find that rupture directivity adjustments using a simple median and aleatory adjustment approach can affect hazard both from a site-specific perspective and on a regional scale, increasing ground motions off the end of the fault trace up to 30%–40% and potentially reducing it for sites along strike. Statewide hazard maps of California show that the change in shaking along major faults can be a factor to consider for assessing long-period [Formula: see text] near-source effects within the USGS NSHM going forward, reaching up to 10%–20%. Finally, we suggest consideration of minimum parameter ranges and baseline requirements as future DMs are developed to minimize single approach adaptations to enable more consistent application within both ground motion and hazard studies.

Remote sensing observations of Searles Lake following the 2019 moment magnitude 7.1 Ridgecrest, California, earthquake reveal an area where surface ejecta is arranged in a repeating hexagonal pattern that is collocated with a solution-mining operation. By analyzing geologic and geotechnical data, here we show that the hexagonal surface ejecta is likely not a result of liquefaction. Instead, we propose dissolution cavity collapse (DCC) as an alternative driving mechanism. We support this theory with pre-event Interferometric Synthetic Aperture Radar data, which reveals differential subsidence patterns and the creation of subsurface void space. We also find that DCC is likely triggered at a lower shaking threshold than classical liquefaction. This and other unknown mechanisms can masquerade as liquefaction, introducing bias into liquefaction prediction models that rely on liquefaction inventories. This paper also highlights the opportunities and drawbacks of using remote sensing data to disentangle the complex factors that influence earthquake-triggered ground failure.

The US National Seismic Hazard Model (NSHM) was updated in 2023 for all 50 states using new science on seismicity, fault ruptures, ground motions, and probabilistic techniques to produce a standard of practice for public policy and other engineering applications (defined for return periods greater than ∼475 or less than ∼10,000 years). Changes in 2023 time-independent seismic hazard (both increases and decreases compared to previous NSHMs) are substantial because the new model considers more data and updated earthquake rupture forecasts and ground-motion components. In developing the 2023 model, we tried to apply best available or applicable science based on advice of co-authors, more than 50 reviewers, and hundreds of hazard scientists and end-users, who attended public workshops and provided technical inputs. The hazard assessment incorporates new catalogs, declustering algorithms, gridded seismicity models, magnitude-scaling equations, fault-based structural and deformation models, multi-fault earthquake rupture forecast models, semi-empirical and simulation-based ground-motion models, and site amplification models conditioned on shear-wave velocities of the upper 30 m of soil and deeper sedimentary basin structures. Seismic hazard calculations yield hazard curves at hundreds of thousands of sites, ground-motion maps, uniform-hazard response spectra, and disaggregations developed for pseudo-spectral accelerations at 21 oscillator periods and two peak parameters, Modified Mercalli Intensity, and 8 site classes required by building codes and other public policy applications. Tests show the new model is consistent with past ShakeMap intensity observations. Sensitivity and uncertainty assessments ensure resulting ground motions are compatible with known hazard information and highlight the range and causes of variability in ground motions. We produce several impact products including building seismic design criteria, intensity maps, planning scenarios, and engineering risk assessments showing the potential physical and social impacts. These applications provide a basis for assessing, planning, and mitigating the effects of future earthquakes.

We evaluate Cascadia subduction ground-motion models (GMMs), considered for the 2023 US National Seismic Hazard Model (NSHM) update, by comparing observations to model predictions. The observations comprise regional recordings from intraslab earthquakes, including contributions from 2021 and 2022 events in southern Cascadia and global records from interface earthquakes. Since the 2018 NSHM update, new GMMs for Cascadia have been published by the Next Generation Attenuation (NGA)-Subduction Project that require independent evaluation. In the regional intraslab comparisons, we highlight a characteristic frequency dependence for Cascadia data, with short periods having lower ground motions and longer periods being comparable to other subduction zones. We evaluate differences in northern and southern Cascadia and find that the NGA-Subduction GMMs developed using southern Cascadia data perform better in this region than the model that did not consider these data. We compare ground-motion variability in Cascadia with the NGA-Subduction model predictions and find differences at short periods ( T = 0.1 s) due to the use of global versus regional data in the development of these models. Moreover, the within-event component of aleatory variability from the GMMs overpredicts the standard deviation of Cascadia recordings at very short periods ( T < 0.05 s). Using global interface earthquakes as a proxy to evaluate the Cascadia GMMs, we find long-period overprediction from a simulation-based GMM and some of the empirical GMMs. When comparing recent observations, we find a similar misfit to GMMs and the 2010 and 2022 Ferndale earthquakes. Finally, we observe different basin amplification factors arising in different subsets of the data, which indicate that differences in basin factors between empirical GMMs could arise from the data selection choices by the developers. As part of evaluating the regional basin terms, we apply basin amplification factors from the magnitude 9 Cascadia earthquake simulations to the empirical GMMs for interface earthquakes. The comparisons presented in this study indicate that the NGA-Subduction GMMs for Cascadia perform well relative to observations and older subduction GMMs.

We develop basin-depth-scaling models (i.e. “basin terms”) from the long-period ([Formula: see text]) simulated ground motions of the Southern California Earthquake Center (SCEC) CyberShake project for use in seismic hazard analyses at sites within the sedimentary basins of southern California. Basin terms use the Next Generation Attenuation (NGA)-West-2 ground-motion models (GMMs) as reference models and use their functional forms with slight modifications. We investigate the use of two approaches to incorporate the time-averaged shear-wave velocity in the upper 30 m ([Formula: see text]) in these calculations and find that the use of site-specific and uniform [Formula: see text] has minor effects on the resulting basin terms for this data set. By centering the simulated ground motions on the basin terms, we separate the information from the simulations about absolute ground-motion level from information relating to the relative amplifications, such as the differences between shallow- and deep-basin sites. Recent observations from sedimentary basins of southern California indicate that additional amplification effect may persist at relatively shallow basin depths (i.e. the GMM basin terms should have positive values when differential depths, [Formula: see text], are near zero), and we present models for “centered” and “adjusted” basin-depth scaling models that reflect this potential. The simulation-modified GMMs are appropriate for crustal sources and for deep-basin sites ([Formula: see text]) within basins of the Greater Los Angeles region, for the magnitudes and distances defined by each of the reference NGA-West-2 GMMs.

We update the ground-motion characterization for the 2023 National Seismic Hazard Model (NSHM) for the conterminous United States. The update includes the use of new ground-motion models (GMMs) in the Cascadia subduction zone; an adjustment to the central and eastern United States (CEUS) GMMs to reduce misfits with observed data; an updated boundary for the application of GMMs for shallow, crustal earthquakes in active tectonic regions (i.e. western United States (WUS)) and stable continental regions (i.e. CEUS); and the use of improved models for the site response of deep sedimentary basins in the WUS and CEUS. Site response updates include basin models for the California Great Valley and for the Portland and Tualatin basins, Oregon, as well as long-period basin effects from three-dimensional simulations in the Greater Los Angeles region and in the Seattle basin; in the CEUS, we introduce a broadband (0.01- to 10-s period) amplification model for the effects of the passive-margin basins of the Atlantic and Gulf Coastal Plains. In addition, we summarize progress on implementing rupture directivity models into seismic hazard models, although they are not incorporated in the 2023 NSHM. We implement the ground-motion characterization for the 2023 NSHM in the US Geological Survey’s code for probabilistic seismic hazard analysis, nshmp-haz-v2, and present the sensitivity of hazard to these changes. Hazard calculations indicate widespread effects from adjustments to the CEUS GMMs, from the incorporation of Coastal Plain amplification effects, and from the treatment of shallow-basin and out-of-basin sites in the San Francisco Bay Area and Los Angeles region, as well as locally important changes from subduction-zone GMMs, and from updated and new WUS basins.

Modern research often involves the collection or analysis of data and the use of specialized computer algorithms. Traditional text articles thus provide only partial documentation of a research study. Readers have limited ability to reproduce or utilize work if the source data are not available or if it relies on an algorithm that is described, but code is not provided. Fortunately, a wide variety of tools are now available to support the publication of research data and code. The effort required to publish data is now relatively small, and the benefits can be immense. This opinion article discusses trends toward increased sharing in academic publishing. It describes opportunities and resources to support data and code sharing and describes the benefits for both authors and readers. Finally, it discusses how Earthquake Spectra is providing resources and enhancing its policies to establish the sharing of data as the default procedure when publishing in the journal, and encourage the sharing of code and other resources.

Genome structural variations within species are rare. How selective constraints preserve gene order and chromosome structure is a central question in evolutionary biology that remains unsolved. Our sequencing of several genomes of the appendicularian tunicateOikopleura dioicaaround the globe reveals extreme genome scrambling caused by thousands of chromosomal rearrangements, although showing no obvious morphological differences between these animals. The breakpoint accumulation rate is an order of magnitude higher than in ascidian tunicates, nematodes,Drosophila,or mammals. Chromosome arms and sex-specific regions appear to be the primary unit of macrosynteny conservation. At the microsyntenic level, scrambling did not preserve operon structures, suggesting an absence of selective pressure to maintain them. The uncoupling of the genome scrambling with morphological conservation inO. dioicasuggests the presence of previously unnoticed cryptic species and provides a new biological system that challenges our previous vision of speciation in which similar animals always share similar genome structures.

Autologous fat grafting is hampered by unpredictable outcomes due to high tissue resorption. Hydrogels based on enzymatically pretreated tunicate nanocellulose (ETC) and alginate (ALG) are biocompatible, safe, and present physiochemical properties capable of promoting cell survival. Here, we compared in situ and ex situ crosslinking of ETC/ALG hydrogels combined with lipoaspirate human adipose tissue (LAT) to generate an injectable formulation capable of retaining dimensional stability in vivo. We performed in situ crosslinking using two different approaches; inducing Ca2+ release from CaCO3 microparticles (CMPs) and physiologically available Ca2+ in vivo. Additionally, we generated ex situ-crosslinked, 3D-bioprinted hydrogel-fat grafts. We found that in vitro optimization generated a CMP-crosslinking system with comparable stiffness to ex situ-crosslinked gels. Comparison of outcomes following in vivo injection of each respective crosslinked hydrogel revealed that after 30 days, in situ crosslinking generated fat grafts with less shape retention than 3D-bioprinted constructs that had undergone ex situ crosslinking. However, CMP addition improved fat-cell distribution and cell survival relative to grafts dependent on physiological Ca2+ alone. These findings suggested that in situ crosslinking using CMP might promote the dimensional stability of injectable fat-hydrogel grafts, although 3D bioprinting with ex situ crosslinking more effectively ensured proper shape stability in vivo.

Gelatinous zooplankton are increasingly recognized to play a key role in the ocean's biological carbon pump. Appendicularians, a class of pelagic tunicates, are among the most abundant gelatinous plankton in the ocean, but it is an open question how their contribution to carbon export might change in the future. Here, we conducted an experiment with large volume in situ mesocosms (~55-60 m3 and 21 m depth) to investigate how ocean acidification (OA) extreme events affect food web structure and carbon export in a natural plankton community, particularly focusing on the keystone species Oikopleura dioica, a globally abundant appendicularian. We found a profound influence of O. dioica on vertical carbon fluxes, particularly during a short but intense bloom period in the high CO2 treatment, during which carbon export was 42%-64% higher than under ambient conditions. This elevated flux was mostly driven by an almost twofold increase in O. dioica biomass under high CO2 . This rapid population increase was linked to enhanced fecundity (+20%) that likely resulted from physiological benefits of low pH conditions. The resulting competitive advantage of O. dioica resulted in enhanced grazing on phytoplankton and transfer of this consumed biomass into sinking particles. Using a simple carbon flux model for O. dioica, we estimate that high CO2 doubled the carbon flux of discarded mucous houses and fecal pellets, accounting for up to 39% of total carbon export from the ecosystem during the bloom. Considering the wide geographic distribution of O. dioica, our findings suggest that appendicularians may become an increasingly important vector of carbon export with ongoing OA.

When a notable earthquake occurs in the United States, a range of familiar real- and near-real-time products are produced by the U.S. Geological Survey (USGS) Advanced National Seismic System (ANSS), and made available via the ANSS Comprehensive Earthquake Catalog. For historical and early instrumental earthquakes, similar results and products are developed depending on data availability and event significance, drawing from published later studies. The year 2023 marked the ninetieth anniversary of the 11 March 1933 Long Beach, California, earthquake. This anniversary provided the impetus to update ANSS products, drawing on archived and published data. Here, we describe the updated ShakeMap, shaking recordings and intensities, and retrospective aftershock forecast for the Long Beach, California, earthquake. In effect we have developed standard, modern ANSS products for an earthquake that occurred 90 yr ago. Our results show that the distributions of both the ground motions, anchored by three strong-motion recordings, and aftershock magnitudes are consistent with expectations for an M 6.4 mainshock in Southern California. We show that, notwithstanding possible limitations, instrumentally recorded accelerations from the closest station are consistent with predicted shaking and directly estimated macroseismic intensities. Updated data products have been added to the USGS event page, where they are available for download. Public-facing products were also created for the anniversary and are freely available on the USGS website.