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1,659 records · Page 90Linked to original sources

USGS2024

Simulated ground-motion records for the seismic assessment of monumental masonry structures

Earthquakes are natural disasters that can cause widespread devastation and loss of life. Simulated ground-motion records can be useful in regions with limited seismic stations or a history of damaging but infrequent earthquakes. This is especially true in areas with a high concentration of heritage masonry structures, which are especially susceptible to damage, as simulated records can be crucial in predicting their seismic response and protecting these buildings from seismic damage. Despite the importance of simulated earthquakes, few studies have investigated how effective they are compared to real earthquakes when assessing the structural response of heritage buildings. To address this knowledge gap, we employ two different simulation methods of the Mw 6.2 Faial earthquake, which occurred on July 9th, 1998, in the Azores, to replicate the recorded time-series at four available stations within an epicentral distance of 150 km. The study has two objectives: first, to validate the simulated records of the 1998 Faial earthquake using alternative stochastic ground-motion simulation approaches, and second, to determine how these approaches impact the seismic assessment of historic masonry structures. To accomplish these objectives, this study uses real and simulated ground-motion datasets to conduct non-linear response history analyses of the São Francisco Church, a monumental structure in Horta that sustained damage during the Faial earthquake. The results show that both simulation approaches yield structural responses similar to the observed records.

Conference Paper↗

USGS2025

Anomalous shear stress variation in wet granular medium: Implications for landslide lateral faults

Landslide assessments typically focus on the mechanical properties of the basal shear zone, but lateral faults are frequently overlooked, possibly due to their lower normal stresses and variably saturated conditions. Using double-cylinder shear experiments on wet granular systems as analogs for landslide lateral faults, we observe anomalous shear stress variations with fluid volume fractions, defying an expected unimodal relationship associated with capillary cohesion. At low fluid volume fractions, shear strength weakens as the wet grain assembly experiences reduced lateral pressure and increased boundary slip. This boundary slip subsequently vanishes, with an abrupt strengthening due to the dilation of the grain assembly against fluid surface tension as saturation approaches. Strike-slip motion and confinement in this system explain the strength anomaly, highlighting a critical role of lateral faults in landslide stability, particularly in cases where dynamics cannot be adequately explained by monitored pore-water pressure or basal friction.

Geophysical Research Letters↗

USGS1977

Acid-rain weathering of a metasedimentary rock basin, Herkimer County, New York

A geochemical balance of major chemical constituents of precipitation inflow with those of surface-water outflow was used to evaluate the effect of acid rainfall (average pH = 4.3) on weathering rates of metasedimentary rocks underlying a surface-water basin in New York State. Precipitation samples and surface-water samples show that approximately 45 percent of the net cation outflow is due to weathering by precipitation acidity. The remaining 55 percent of the cation load in the outflow is attributed to interactions between atmosphere, rock, and soil water in the unsaturated zone. Comparison of the acidity of acid precipitation and air-equilibrated distilled water suggests that since preindustrial time, precipitation acidity has probably increased weathering rates for this basin approximately 75 percent. The increased acidity of the precipitation may also increase the rate of dissolution of heavy metals from water-piping systems.

New York↗

USGS2026

Variable pH habitats could help prepare stone crabs for coastal acidification

Coastal acidification is being exacerbated by terrestrial organic inputs, especially after high precipitation events. Florida’s rainy season coincides with stone crab ( Menippe mercenaria) reproduction, and pH extremes could limit future harvests by reducing reproductive output. Populations that experience pH variability can serve as “natural laboratories” for estimating the tolerance of a species to coastal acidification. Here, we conducted a series of experiments to determine if ovigerous stone crabs conditioned in more variable pH habitats (seagrass) would result in faster embryonic development, greater hatching success, and higher larval survival relative to crabs conditioned in habitats with lower pH variability (sandy habitats). After field conditioning, crabs were transported to the laboratory and randomly acclimated to either a control pH (pH = ~ 7.90) or a reduced pH condition (pH = ~ 7.60) until larval release. The rate of embryo development was slower in the laboratory reduced pH treatment, however, there were no observable field condition effects on embryo development rate. Crabs conditioned in the more pH variable seagrass habitat did have greater hatching success and higher larval survival than crabs in less pH variable sandy habitats; however, larval survival was low across all treatments. These results suggest that the pH variability experienced in seagrass habitats during brooding may serve as a mechanism for stone crabs to acclimatize to extremes in seawater pH.

Marine Biology↗

USGS2025

Annual NLCD (National Land Cover Database)—The next generation of land cover mapping

Introduction The widely used National Land Cover Database (NLCD) has long been the foundational land cover source for scientists, resource managers, and decision makers across the United States. In 2024, a reinvention as Annual NLCD added the key improvement of annual time steps to show decades of change at a higher frequency than the intervals of 2–3 years used in the legacy NLCD. Annual NLCD was derived primarily from the long Landsat satellite data record, and it includes data from other sources. The first release in 2024 of Annual NLCD provides Collection 1.0 of products encompassing land cover and land change from 1985 through 2023 for the conterminous United States (CONUS). The Annual NLCD Collection 1.0 consists of six operational products that map the unique characteristics of land cover. A map created from Annual NLCD shows 16 land cover classes for the CONUS in 2023.

conterminous United States↗

USGS2024

Imaging of seismic discontinuities using an adjoint method

For imaging of seismic discontinuities at depth, reverse time migration (RTM) is a powerful method to apply to recordings of seismic events. It is especially powerful when an extensive receiver array, numerous seismic sources, or both, permit adequate reconstruction of incident and scattered wavefields at depth. Reconstructing either the incident or scattered wavefield at depth becomes less accurate when relatively few recordings of seismic events are available. Here we explore an inverse scattering approach to imaging discontinuities based on an adjoint method, employing sensitivity kernels (Frechet derivatives) that represent jumps in material properties across seismic-discontinuity surfaces. When combined with ray-based requirements on scattering geometry, it constitutes a powerful approach to determining the locations and amplitudes of the discontinuities, recovering only those properties that can be resolved by a spatially limited source and/or receiver distribution. This is illustrated by synthetic examples with local sources followed by a field example in a subduction zone setting

Washington↗

USGS2024

Predictions of groundwater PFAS occurrence at drinking water supply depths in the United States

Per- and polyfluoroalkyl substances (PFAS), known colloquially as “forever chemicals”, have been associated with adverse human health effects and have contaminated drinking water supplies across the United States owing to their long-term and widespread use. People in the United States may unknowingly be drinking water that contains PFAS because of a lack of systematic analysis, particularly in domestic water supplies. We present an extreme gradient boosting model for predicting the occurrence of PFAS in groundwater at the depths of drinking water supply for the conterminous United States. Our model results indicate that 71 to 95 million people in the conterminous United States potentially rely on groundwater with detectable concentrations of PFAS for their drinking-water supplies prior to any treatment.

conterminous United States↗

USGS2024

Deep syntectonic burial of the Anthracite belt, Eastern Pennsylvania

Fluid inclusion microthermometry and Raman spectroscopy of fluid inclusions in quartz veins from the Pennsylvanian rocks of the Anthracite belt, eastern Pennsylvania support a deep burial model of coalification in favor of focused orogenic hot fluid flow. High-temperature (250 to 255 °C) trapping of CH 4 ± CO 2 saturated aqueous fluids and CH 4 ± CO 2 inclusions indicate fluid trapping at depths of 11.5 to 13.4 km under a cover of Pennsylvanian to Permian(?) syntectonic load. In the folded rocks to the south of the Anthracite belt, CH 4 ± CO 2 fluid inclusions indicate a sediment load that was up to 16.3 km thick. Re -equilibrated aqueous fluid inclusions from veins in Silurian through Devonian rocks give the same range of trapping conditions but a wide range of fluid salinities suggesting that folding, fracturing, and meteoric recharge resulted in the intermixing of fluids from throughout the stratigraphic succession.

Pennsylvania↗

USGS2024

topoBuilder quick start guide

TopoBuilder is a public web application from the National Geospatial Program that enables anyone to create customized digital U.S. Geological Survey (USGS) topographic maps, called OnDemand Topos, with the best available, most up-to-date data from The National Map (nationalmap.gov). OnDemand Topos can be made at different scales or quadrangles and can cover anywhere within the United States and its territories.

Fact Sheet↗

USGS1977

Exploratory water well, St. George Island, Florida

A 1,026-foot well was drilled into the Floridan aquifer on St. George Island in search of a supply of water for residential development in 1971. This is the only well on the island on record to have been drilled below 200 feet for water. The well was abandoned; water flowing from the well was saline. It had a specific conductance of 7,500 micromhos per centimeter at 25° Celsius. The specific conductances of samples taken at drilling depths 217-1,026 feet ranged from 3,140 to 39,600, with the maximum value at 470 ft. A composite geophysical and lithologic log of the well shows spontaneous potential, single-point resistance, gamma-ray, neutron, gamma-gamma, and caliper logs. Well-site notes, a written description of cuttings samples, a graph showing the relation of specific conductance of water samples to the depth of the well at time of sampling, and four chemical analyses of the water are included in the report.

Florida↗

USGS2026

Relating glassy rind thicknesses to ambient air temperatures at the Lost Jim flow field in the Imuruk Lake volcanic field, Alaska

The Lost Jim flow field, in the Imuruk Lake volcanic field, Alaska, extends west ~34 km from a single vent, crossing subarctic tundra and currently touches several lakes and streams. The weighted mean of five 36Cl cosmogenic exposure ages from the Lost Jim pāhoehoe flow is 7.73 ± 0.37 ka, indicating this eruption occurred substantially after the eruption of the underlying Camille flow, which was emplaced at 39.7 ± 1.3 ka. Paleoclimate records indicate the period when the Lost Jim flow field was emplaced was after deglaciation, and the climate was similar to today. We propose that the emplacement of lava in these cold subarctic conditions can lead to faster cooling of the lava surface compared to lava emplaced in warmer locations such as mid- latitude cold deserts. Glass abundance in the outermost rinds at the Lost Jim flow field was on average 74 % with 6.4 mm thick rims, compared to 60 % with 2.9 mm rims for cold mid-latitude desert samples. We interpret increased glass content as a proxy for rapid cooling likely occurring partly during winter. Glassiness values varied less across vent, margin, and mid-flow locations when compared to the mid-latitude flows suggesting the Lost Jim flow field was broadly impacted by the subarctic climate as opposed to responding to local microclimates. Our results indicate that lava glassiness may be a useful environmental indicator of cooler (in this case subarctic) conditions.

Alaska↗

USGS2025

Improved prediction of postfire debris flows through rainfall anomaly maps

Predicting where runoff-generated debris flows might occur during rainfall on steep, recently burned terrain is challenging. Studies of mass-movement processes in unburned areas indicate that event locations are well-predicted by rainfall anomaly, R* , in which peak observed rainfall is normalized by local rainfall climatology. Here, we use remote and field methods to map debris flows triggered within the 2020 Dolan Fire burn area in coastal California, demonstrate that a short-duration R* metric predicts debris-flow occurrence more effectively than absolute peak intensity or longer-duration rainfall metrics, and show that incorporating an R* criterion into an existing debris-flow likelihood model can reduce false positive predictions and improve accuracy. We test R * at three other climatically distinct fires in California, demonstrating its utility for mapping likely debris-flow locations in different climates. We also consider how R* can benefit postfire debris-flow prediction given recent increases in climatological variability within individual burn perimeters.

Callifornia↗

USGS2026

Temperate wetlands lose climate-cooling capacity under warming

Temperate inland wetlands have long been viewed as climate regulators, with sustained CO₂ sequestration offsetting continuous CH₄ emissions over centennial–millennial timescales. However, the net climatic effect of these opposing fluxes remains uncertain under anthropogenic warming as they differ in both magnitude and atmospheric lifetime. We combine 19,000 CH₄ chamber measurements from 202 temperate inland wetlands with carbon burial rates from 16 dated sediment cores in North America’s Prairie Pothole Region to estimate greenhouse gas dynamics over two centuries. Here we show that CH₄ emissions rise by ~1.39 kg CH₄ ha⁻¹ yr⁻¹ over the historical period and are projected to approach 950 kg CH₄ ha⁻¹ yr⁻¹ under high-forcing scenarios by 2100, while CO₂ sequestration is expected to decline by ~0.3 kg CO₂ ha⁻¹ yr⁻¹, driving a shift toward persistent net CO₂-equivalent source behaviour and a weakening of the long-term cooling effect that wetlands have provided under natural conditions.

Prairie Pothole Region↗

USGS2025

Ecohydrological response of a forested headwater catchment to a flash drought in the Southeastern U.S.

Flash droughts differ from traditionally defined droughts in their rapidity of intensification and often associated high vapor-pressure deficit. These droughts can lead to declines in streamflow and water table depth and induce water stress to vegetation at a greater rate than droughts that manifest over longer periods. However, little is known regarding the response of forested environments to flash drought because most studies of impacts have been conducted in agricultural settings. In this study we investigated water-use patterns of riparian trees using sap flow methods and examined the role of groundwater as a source of moisture over three periods that were delimited by antecedent soil moisture conditions. For a longer-term perspective we also examine monthly streamflow over the 35-year record. We observed that trees at only one monitoring plot showed a decrease in water use relative to evaporative demand during a flash drought. Total reverse sap flow (flow toward the roots rather than the canopy) greatly increased during the flash drought period, suggesting the likely occurrence of hydraulic redistribution to the excessively dry soils. Over the drought period groundwater became a more dominant source of moisture for sustaining forest water use. Monthly mean streamflow during the flash drought approached levels observed in past multiyear droughts. This is the first study, to our knowledge, to specifically investigate the response of multiple water budget components to flash drought in a humid forest. As more studies are conducted, a better understanding of the range of expected responses are likely to emerge.

Georgia↗

USGS2025

Ultralong, supershear rupture of the 2025 Mw 7.7 Mandalay earthquake reveals unaccounted risk

The 28 March 2025 moment magnitude ( M w ) 7.7 earthquake in Mandalay, Burma (Myanmar), ruptured 475 kilometers of the Sagaing Fault, which was more than twice the length predicted by magnitude scaling relationships. Kinematic slip models and observation of a Rayleigh Mach wave that passed through parts of Thailand confirmed that rupture occurred at supershear velocities of greater than 5 kilometers per second. The anomalous length exposed a vast population to violent near-fault shaking. The Mandalay earthquake is a modern analog for the M w 7.9 1906 San Francisco earthquake, another atypically long and fast rupture. Probabilistic seismic hazard analyses use scaling relations that do not account for such long ruptures at moderate magnitudes. This limitation, in conjunction with a likely increased population and infrastructure exposure for atypically long ruptures, contributes to a potential mischaracterization of seismic risk.

Mandalay↗

USGS2024

Summary of annual repeat magnetotelluric surveys of the Geysers geothermal field

As part of a multi-year project, funded by the California Energy Commission, annual magnetotelluric (MT) surveys have been collected at The Geysers geothermal field in northern California with the goal of measuring temporal changes within the steam field. The repeat surveys started in 2021 and repeated a 2017 survey (Peacock et al., 2020) with further extension to the southern part of the geothermal field. Temporal variations in the MT transfer functions are observed to be spatially coherent and compartmentalized. Mapping residual phase tensor ellipses demonstrates the direction of maximum change is often aligned with existing fracture orientations. Three dimensional inversion of the MT data, using the inversion results from previous years as the starting model, indicates that the steam reservoir has generally become more resistive over time (~10%), suggesting more steam in the field. A few pockets within the steam field have become more electrically conductive over time and are collocated with injection wells, suggesting either more fluid content in those zones, less steam, or more saline fluids.

California↗

USGS2025

Prospectivity modeling of the NASA VIPER landing site at Mons Mouton near the Lunar South Pole

We use a high-resolution digital elevation model and a numerical thermal model to produce a variety of inputs for a water-ice prospectivity model for the Volatiles Investigating Polar Exploration Rover (VIPER) landing site. These input data are maps of topography, surface slope, surface aspect, surface curvature, maximum temperature, depth to ice stability, permanently shadowed regions (PSRs), distance to PSRs, and PSR density. This model predicts where water ice is most likely within the top meter of regolith, assuming plausible relationships between ice concentration and the various inputs. The model is designed to be adjusted in near-real time as data are collected during the VIPER mission. As such, it is a tool for both analyzing data from the mission as well as planning operations. Since the current model, at this point, relies only on orbital remote sensing, the final version will also be a tool to extrapolate the VIPER mission results across the lunar poles.

Planetary Science Journal↗

USGS2026

Magnitude conversion relations create substantial differences in seismic hazard models

Earthquake catalogs are essential data inputs for seismic hazard modeling. Because earthquake magnitudes are reported in a variety of types (e.g., local magnitudes and moment magnitudes), magnitude conversion relationships must be used to convert the different magnitude types present in a catalog to a uniform magnitude type to avoid biases in the hazard computation. However, these conversion relationships are often uncertain and have been shown to sometimes perform poorly. Here, we investigate the sensitivity of the gridded seismicity component of the National Seismic Hazard Model (NSHM) to the catalog conversion equations in the Eastern United States. In the 2023 NSHM, magnitudes of various types were converted to moment magnitudes using equations developed by the Central and Eastern United States Seismic Source Characterization for Nuclear Facilities (CEUS‐SSCn), based on least‐squares (LS) regressions made using data from a catalog containing events up through 2008. We recompute these equations using events in the Advanced National Seismic System Comprehensive Earthquake Catalog with multiple magnitudes from 2000 to 2023. Although we prefer the use of orthogonal regressions for our datasets, LS regressions produce broadly similar results, with both approaches exhibiting large deviations from the CEUS‐SSCn conversions, especially at smaller magnitudes. We compare the spatial distribution of annual rates using three different models: (1) the 2023 NSHM conversions, (2) our updated conversions, and (3) no conversions. We find that the choice of conversions leads to substantial differences in the rate forecasts, which can greatly impact the seismic hazard model, particularly in regions with low‐seismicity rates such as the Eastern United States, where the hazard is dominated by gridded seismicity rather than a fault model.

Seismological Research Letters↗