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1,662 records · Page 32Linked to original sources
USGS2026

ShakeAlert Earthquake Early Warning System performance during the Mw 7.0 offshore Cape Mendocino earthquake

The 5 December 2024 M w 7.0 Offshore Cape Mendocino earthquake was a challenging test of the U.S. West Coast ShakeAlert earthquake early warning system due to its offshore epicenter and limited near‐source station coverage. We analyzed real‐time performance of all components of the ShakeAlert system, including the seismic algorithms (earthquake point‐source integrated code [EPIC] and Finite‐fault rupture Detector [FinDer]), the geodetic algorithm (Geodetic First Approximation of Size and Time–peak ground displacement [GFAST‐PGD]), and network telemetry during the event. EPIC created the first solution for this earthquake 15 s after origin time with an initial magnitude estimate of M 5.6 and location error of 10 km from the Advanced National Seismic System epicenter. An early spurious trigger from station CE.89101 fortuitously maintained location accuracy and, correspondingly, magnitude accuracy. FinDer contributed its first solution at 18 s with a location estimate closer to the seismic network and produced two distinct rupture geometries, leading to minor fluctuations in estimated intensity contours. GFAST‐PGD did not meet alerting thresholds but otherwise performed as expected. Network latencies were <2 s for most stations, supporting the rapid detection of this earthquake by the system. Roughly five million alerts were delivered to cell phone devices in California and Oregon during this event. This was also the first instance of a school district‐wide ShakeAlert‐powered system being activated. Comparisons to recorded seismograms demonstrate that the maximum warning times before potentially damaging shaking (intensity 6+) were in the range of 5–55 s. Although the ShakeAlert system provided accurate solutions and useful alert delivery, this earthquake raised awareness of potential issues within the system, including the need for improved offshore location estimates, a combination of solutions from ShakeAlert servers, and handling of spurious triggers.

California↗
USGS2025

Protected from Pterygoplichthys? Predicting thermal habitat suitability for nonnative armored catfish in the Suwannee River

Objective Nonnative fishes can modify ecosystems and harm economies when they are introduced to new environments. Climate change is likely to assist the spread and establishment of some nonnative fishes (e.g., warmwater species), but spatiotemporal gaps in water temperature monitoring and modeling may prevent ecologists and managers from forecasting thermal habitat suitability for these taxa. The purpose of this study was to develop a predictive model of winter water temperatures and thermal habitat suitability for two priority nonnative armored catfish, Vermiculated Sailfin Catfish Pterygoplichthys disjunctivus and Orinoco Sailfin Catfish P. multiradiatus , in the Suwannee River, Florida and Georgia. Methods Precipitation- and groundwater-corrected air–water temperature models were developed and evaluated using a model selection procedure to predict water temperatures at four sites in the Suwannee River. These models were chosen because they blend the simplicity of air–water temperature models with the accuracy of hydrometeorological models to create an efficient, economical, management-relevant approach for analyzing and forecasting water temperature. Results Most of the top-performing water temperature models (92%) had precipitation or groundwater corrections to air–water temperature formulations. Projected mean and maximum water temperatures increased as simulated climate change intensified. All four Suwannee River sites studied were projected to be thermally hospitable to the survival of Vermiculated Sailfin Catfish. Lower river sites, noticeably warmer than upper river sites, were conducive to the survival of Orinoco Sailfin Catfish throughout the winter months. The upper river sites were too cold for Orinoco Sailfin Catfish survival in some climate-change scenarios, but the Suwannee River has an abundance of constant-temperature springs that are likely hospitable to Vermiculated Sailfin Catfish and Orinoco Sailfin Catfish throughout the year. Conclusions The findings suggest that winter water temperatures will likely not be a barrier to the survival of Pterygoplichthys catfish in the Suwannee River, amplifying the importance of conservation and management approaches to inhibit their spread and establishment. If the Pterygoplichthys population remains small and isolated and decision makers are able to devote required staff time and resources to managing these species, removal and eradication at local if not broader scales may be reasonable goals. This study provides a water temperature modeling approach that can aid ecologists and managers in prioritizing sites to prevent the introduction, slow the dispersal, eradicate, and control Pterygoplichthys catfish and other nonnative fishes in the Suwannee River and beyond.

Florida, Georgia↗
USGS2026

Digitizer Suite: The Albuquerque Seismological Laboratory Digitizer Testing Suite

Laboratory testing of digitizers and seismometers helps ensure that prior to deployment the instrumentation can produce high quality data and is operating within specifications. In this work we detail the software package called: the Albuquerque Seismological Laboratory (ASL) Digitizer Test Suite. This Java software package provides several algorithms to verify various performance parameters of digitizers commonly used for recording analog seismic instruments. The goal of these tests is not to be exhaustive, but to identify common failures that could compromise the integrity of seismic data being recorded on the digitizer. For example, Sandia National Laboratories (e.g., Slad and Merchant, 2018) routinely do comprehensive testing of digitizers for various monitoring missions. While these tests reports are valuable for comprehensively characterizing a recording system, it would be resource intensive to conduct such tests on every seismic recorder used in a network. We focus on tests that include ways to estimate the sensitivity, timing, self-noise, and clip-level of the digitizer, as well as the fidelity of the signal being recorded. The software is publicly available and provides a way for the community to verify the integrity of a digitizer using a minimum amount of outside equipment.

Seismological Research Letters↗
USGS2025

Modeling interconnected minerals markets with multicommodity supply curves: Examining the copper-cobalt-nickel system

Demand for many of the metals used in the energy transition is expected to grow rapidly. Many of these are by-products, often considered critical because their production responds weakly to prices and is instead tied to the economics of the host mineral. We present a model of prices and production for jointly produced commodities that accounts for interconnectivity between host and by-product markets at the mine level. We demonstrate this method using the copper–cobalt–nickel system, in which approximately 99% of cobalt is a by-product of copper or nickel mining. Our results show that the model more accurately captures the economic benefits of diversified mine outputs than previous approaches. Furthermore, changes in demand drivers for any two commodities produce non-linear effects on production and price. We challenge the prior best-practice assumption that cobalt cannot impact the copper or nickel markets. Recognizing the importance of both copper and cobalt for future electrification, we emphasize that incentivizing the copper industry to reduce cobalt supply risks could inadvertently undermine copper supply.

Nature Communications↗
USGS2026

Lithium brine potential of North Dakota: Results from the 2025 sampling program

Lithium (Li), classified as a critical mineral and key in energy storage applications because of its high energy density, faces unprecedented demand. This has driven interest in unconventional sources of Li, especially brines from sedimentary basins. Accordingly, the spatial distribution of basinal brinehosted Li resources across North America is becoming better defined, including the Williston Basin underlying Saskatchewan, Canada. This has led to growing investment and exploration by industry throughout the 2020s; however, despite this interest, the Li potential of basinal brines of the Williston Basin in North Dakota remain underexplored. This work presents the results from the 2025 joint brine sampling campaign between the North Dakota Geological Survey, the United States Geological Survey (USGS), and The University of Texas at Austin. Twenty-seven fluid samples were collected from producing oil and water source wells from eight stratigraphic intervals across western North Dakota and analyzed for major cation and anion concentrations. Similar to southeastern Saskatchewan, the highest Li concentrations were identified in the Devonian Duperow Formation, with concentrations up to 179 mg/L being observed in a well commingled between the Duperow and Red River Formations. Some samples from the overlying Birdbear Formation exceeded 75 mg/L, whereas Li concentrations were lower in the Madison Group (33-44 mg/L) and the Three Forks (50 mg/L), Dawson Bay (43 mg/L), Winnipegosis (23 mg/L), and Red River (40.0 mg/L) Formations. This work indicates Li resource potential exists across the Williston Basin and advances our understanding of the Li distribution in basinal brines which could provide a new domestic source of this critical mineral.

North Dakota↗
USGS2000

Hydrology and water and sediment quality at James Campbell National Wildlife Refuge near Kahuku, Island of Oahu, Hawaii

The James Campbell National Wildlife Refuge occupies two lowland marsh and pond complexes on the northern coastal plain of Oahu: the mostly natural ponds and wetlands of the Punamano Unit and the constructed ponds of the Kii Unit. The U.S. Fish and Wildlife Service manages the Refuge primarily to protect and enhance habitat for four endangered species of Hawaiian waterbirds. Kii Unit is fed by artesian wells and rainfall, whereas Punamano Unit is fed naturally by rainfall, runoff, and ground-water seepage. Streams drain from the uplands into lowland ditches that pass through Kii Unit on their way to the ocean. A high-capacity pump transfers water from the inner ditch terminus at Kii to the ocean outlet channel. Stormwaters also exit the inner ditch system over flood-relief swales near the outlet pump and through a culvert with a one-way valve. A hydrologic investigation was done from November 1996 through February 1998 to identify and quantify principal inflows and outflows of water to and from the Refuge, identify hydraulic factors affecting flooding, document ground-water/surface-water interactions, determine the adequacy of the current freshwater supply, and determine water and sediment quality. These goals were accomplished by installing and operating a network of stream-gaging stations, meteorology stations, and shallow ground-water piezometers, by computing water budgets for the two Refuge units, and by sampling and analyzing water and pond-bottom sediments for major ions, trace metals, and organic compounds. Streamflow during the study was dominated by winter stormflows, followed by a gradual recession of flow into summer 1997, as water that had been stored in alluvial fans drained to lowland ditches. Outflow at the ditch terminus in 1997 was 125 million gallons greater than measured inflow to the coastal plain, mainly reflecting gains from ground water along the ditches between outlying gages and the ditch terminus. Of the measured 1997 outflow, 98 percent was through the Kii outlet pump, with the outlet culvert valve only opening for brief periods during storms. Large volumes of stormflow overflowed the flood-relief swales unmeasured. The largest storm of the study, in November 1996, was estimated to have a flood frequency of about 3 to 4 years. Streamflow exceeded culvert capacity and overtopped Kamehameha Highway at Kalaeokahipa Stream and Hospital ditch. Slight overbank flooding in Kii ditch resulted strictly from high discharge. Minor overbank flooding farther out on the coastal plain probably was caused mainly by the small hydraulic gradients available to convey stormflows along the lowland ditches. Stormwaters flooded Kii ponds and flowed back upstream along Punamano ditch into Punamano marsh, introducing suspended sediment and possibly other contaminants to the Refuge. Two smaller storms in January 1997 resulted in smaller flows and no overbank flooding. The Kii outlet pump ran continuously for 7 days during the November 1996 storm and for 1 to 2 days during the January 1997 storms. During all three storms, the outlet culvert valve opened and the inner ditches overtopped the flood-relief swales, allowing free outflow of water from the inner ditch. Backwater effects hindered drainage during the January 1997 storms at Hospital ditch at Kamehameha Highway, and at Punamano ditch at Nudist Camp Road (where the backflow into Punamano marsh in November 1996 constituted an extreme backwater effect). A probable marine backwater effect was imposed at the ocean outlet ditch during the November 1996 storm through a combination of high spring tides and wave setup from large surf. Whether this backwater effect propagated upstream in the ditches to affect inland sites could not be determined conclusively. A sand plug may have built up in the ocean outlet channel before the November 1996 storm, but if so, it probably washed out prior to, or early in the storm, and was not present at the time of peak stage at inland sites. A season-long buildup of the sand plug in late 1997 was inferred from rising water levels in the outlet ditch. Seawater flows up the outlet channel or over the sand berm and into the outer ditch system on most high tides, and particularly during spring high tides. Ponds and ditches of the Refuge and surrounding lowlands have mud- and clay-lined bottoms that form an effective confining unit and inhibit interaction with an underlying shallow limestone aquifer. At Kii Unit, pond levels are higher than adjacent ditch levels and underlying ground-water levels, establishing lateral and downward head gradients that could foster seepage losses from the ponds. Regional ground-water discharge from the Koolau aquifer to the coastal-plain sediments is mostly diffuse, but is concentrated where ridges of Koolau Basalt plunge beneath coastal-plain sediments near Punamano Unit and at the head of Hospital ditch. Kii ditch gains brackish ground water downstream of Kamehameha Highway. Wastewater disposal from the sewage treatment plant adjoining Kii Unit poses little or no threat to Refuge habitat. Disposal is at six injection wells located 0.45 mi away at Kahuku, and the wells inject into confined limestone aquifers that do not extend to Kii Unit. The natural freshwater supply to Punamano Unit is adequate for maintaining the wildlife habitat, judging from stable pond levels and low salinities there. A monthly water budget for Punamano showed an apparent annual deficit in measurable flows in 1997, requiring unmeasured ground-water gains equalling 51 inches of water. The freshwater supply to Kii Unit is inadequate according to Refuge managers, because there is not enough water to manipulate levels adequately in the ponds during most of the year, and particularly during the driest months. This is confirmed by monthly deficits in the water budget for the Kii ponds during summer months. However, the Kii budget showed an annual surplus in measurable flows for 1997 equalling 24 inches of water. Unmeasured losses are required to explain the apparent annual surplus, such as discharge to the ditches through pond water-control structures and downward and/or lateral ground-water seepage. The apparent surplus at Kii is strictly hydrologic and is not a surplus in a management sense; it cannot be stored or used to supply the Refuge, but instead reflects losses from the system that render this amount of water unavailable for use. The budget year, 1997, was drier than normal (24 percent below long-term mean rainfall) and so the measured potential evaporation for 1997 was probably higher than the long-term mean. Few metals or organic compounds of potential concern were detected in pond and ditch waters and in pond-bottom sediments. Detected pesticides were at trace levels or just above minimum reporting limits. Exceptions that exceeded quality guidelines for freshwater sediment were copper and zinc in sediment from Kii ponds C and D, and copper in sediment from Punamano north pond. Therefore, urban and agricultural runoff probably have contributed little in the way of harmful metals or organic compounds to the Refuge, although the potential for such contribution remains from periodic flooding of the ponds by ditch stormflows. Salinity was low throughout most Refuge waters, qualifying as fresh to slightly brackish and suitable for the environmental needs of Refuge fauna. Higher salinities have been observed in ditches during past periods of sugarcane cultivation and saltwater aquaculture, however. Resumption of saltwater aquaculture could raise ditch salinities if saltwater effluents are disposed directly into the ditches, as they were in the past.

Hawaii↗
USGS2025

Estimated ultimate recovery (EUR) Prediction for Eagle Ford Shale using integrated datasets and artificial neural networks

The estimated ultimate recovery (EUR) is an important parameter for forecasting oil and gas production and informing decisions regarding field development strategies. In this study, we combined site-specific geologic, completion, and operational parameters with the predictive capabilities of machine learning (ML) models to predict EURs of the wells for the Eagle Ford Marl Continuous Oil Assessment Unit. We developed an extensive dataset of wells that have produced from the lower and upper Eagle Ford Shale intervals and reduced the model complexity using principal component analysis. We tested the ML models and estimated the sensitivities of ML-predicted EURs to changes in the values of different input variables. The results of applying the optimized ML model to the Eagle Ford suggest that the approach developed in this study could be promising. The ML estimates of the EURs fit the DCA-based values with an R 2 ~ 0.9 and a mean absolute error of ~36 × 10 3 bbl. In the lower Eagle Ford Shale, the EUR estimates were found to be most sensitive to changes in porosity, net thickness of the interval, clay volume, and the API gravity of the oil; and that in the upper Eagle Ford Shale they were most sensitive to changes in the total organic carbon and water saturation, which suggests that it could be important to consider these parameters in assessing these intervals or close analogs.

Louisiana, Mississippi, Texas↗
USGS2024

Flood-inundation maps for the Cuyahoga River in and near Independence, Ohio, 2024

Digital flood-inundation maps for a 9.9-mile reach of the Cuyahoga River in and near Independence, Ohio, were created by the U.S. Geological Survey (USGS) in cooperation with the Northeast Ohio Regional Sewer District Board of Trustees. Water-surface profiles were computed for the stream reach by using a one-dimensional steady-state step-backwater model. The model was calibrated to the current (2024) stage-streamflow relation (rating curve 43.0) for the USGS streamgage 04208000, Cuyahoga River at Independence, Ohio. The resulting hydraulic model was then used to compute 13 water-surface profiles for water levels (flood stages) ranging from 14.00 to 26.00 feet. The flood stages range from “action stage” to above “major flood stage” as reported by the National Weather Service. The simulated water-surface profiles were then used in combination with a digital elevation model derived from light detection and ranging data to map the inundated areas associated with each flood profile. The flood-inundation maps and the supporting hydraulic model produced by this study can be used by emergency managers and local officials to assess flood mitigation strategies and to define flood hazard areas to protect life and property, to coordinate flood response activities such as evacuations and road closures, and to aid postflood recovery efforts.

Ohio↗
USGS2024

Bathymetric and velocimetric surveys at highway bridges crossing the Missouri River between Kansas City and St. Louis, Missouri, May 19–26, 2021

Bathymetric and velocimetric data were collected by the U.S. Geological Survey, in cooperation with the Missouri Department of Transportation, near nine bridges at eight highway crossings of the Missouri River between Kansas City and St. Louis, Missouri, from May 19 to 26, 2021. A multibeam echosounder mapping system was used to obtain channel-bed elevations for river reaches about 1,640 to 1,840 feet (ft) longitudinally and generally extending laterally across the active channel from bank to bank during low to moderate flood-flow conditions. These surveys provided channel geometry and hydraulic conditions at the time of the surveys and provided characteristics of scour holes that may be useful in developing or verifying predictive guidelines or equations for computing potential scour depth. These data also may be useful to the Missouri Department of Transportation as a low to moderate flood-flow assessment of the bridges for stability and integrity issues with respect to bridge scour during floods. Bathymetric data were collected around every in-channel pier. Scour holes were present at most piers for which bathymetry could be obtained, except those on banks or surrounded by riprap. Occasionally, scour holes were minor and difficult to discern from nearby dunes and ripples. All the bridge sites in this study were previously surveyed and documented in previous studies. Comparisons between bathymetric surfaces from the previous surveys and those of the current (2021) study do not indicate any consistent correlation between channel-bed elevations and streamflow conditions. The average difference between the bathymetric surfaces varied from 1.59 ft higher to 0.95 ft lower in 2021 than 2017, which corresponds to a gain of 100,200 cubic yards and a loss of 55,800 cubic yards, respectively. The average difference between the bathymetric surfaces varied from 2.74 ft higher to 3.05 ft lower in 2021 than 2013, which corresponds to a gain of 111,500 cubic yards and a loss of 169,200 cubic yards, respectively. The average difference between the bathymetric surfaces varied from 4.52 ft higher to 1.38 ft lower in 2021 than 2011, which corresponds to a gain of 221,100 cubic yards and a loss of 90,300 cubic yards, respectively. The most substantial overall net gain was 221,100 cubic yards between 2011 and 2021 at structures L0550 and A4497 at Jefferson City (site 20). The large net gain likely results from a combination of the mitigation of the scour holes near pier 4 of both bridges and the substantially lower flow in 2021 than in 2011. Alternatively, the most substantial overall net loss was 169,200 cubic yards between 2013 and 2021 at structure A6288 at Hermann (site 21), despite comparable streamflows. Pier size, nose shape, and skew to approach flow had a substantial effect on the size of the scour hole observed at a given pier. Larger and deeper scour holes were present at piers with wide or blunt noses caused by exposed footings or caissons. When a pier was skewed to primary approach flow, the scour hole was generally deeper and larger than at a similar pier without skew; furthermore, the shape of the scour hole near skewed piers in this study generally was longer and deeper on the side with impinging flow. At structure A6288 at Hermann (site 21), the scour hole near pier 5 was difficult to discern from nearby dunes and ripples, whereas the upstream edge of the footing was visible at pier 4, which likely contributes to the larger scour hole near that pier; the top of the footing may blunt the horseshoe vortex at pier 5, but the exposed front of the footing may exacerbate the vortex at pier 4.

Missouri↗
USGS2025

A new groundwater energy transport model for the MODFLOW hydrologic simulator

Heat transport in the subsurface is an important aspect of research related to the effects of a warming climate on ecological services (i.e., cold-water refugia); the development of geothermal resources for energy banking schemes (i.e., aquifer thermal energy storage [ATES]); and the effects of temperature on other aspects of groundwater quality, such as nutrient cycling. Historically, simulation of heat transport using the MODFLOW groundwater simulator and related codes was performed by scaling the input parameters of a solute-transport model to emulate heat transport. However, that approach required additional pre- and post-processing of input and output and could not account for the variation in effective thermal storage and transport properties during transient, unsaturated flow, for example. True heat-transport capabilities in the context of MODFLOW were first introduced in a variant called USG-Transport. More recently, a new groundwater energy-transport (GWE) model type has been added to MODFLOW 6, the core version of the MODFLOW hydrologic simulator. GWE supports the simulation of heat transport on structured or unstructured grids as well as within and between features of advanced packages that represent streams, lakes, multi-aquifer wells, and the unsaturated zone. GWE is integrated within MODFLOW 6 and is accessible through the FloPy Python package and the MODFLOW 6 application programming interface (API). An example simulation demonstrates conduction between grid cells through both the water and the solid aquifer material, including thermal bleeding from saturated overburden cells into a groundwater flow field.

Groundwater↗
USGS2025

Using peak geometry and shifts in the x-ray spectrum of carbon from electron probe microanalysis to determine thermal maturity of organic matter

During the burial of mudstones, the associated organic matter undergoes gradual thermal maturation, a key process that can influence the reactivity of organic matter during catagenesis, the formation of hydrocarbon deposits and the chemical weathering of mudstones. Conventional methods for assessing the thermal maturity of organic matter often fail to reflect the geochemical heterogeneity between individual organic phases in mudstone samples. Here, we report an alternative, non-destructive, surficial and micro-scale (analytical spot size of ~ 300 nm with about 4 μm diffusion depth for micrometre-size organic grains) method to evaluate the thermal maturity of organic matter in mudstones using the carbon K α X-ray spectrum measured by field emission-electron probe microanalyser (FE-EPMA). Using this method, we observed correlations between parameter values derived from FE-EPMA spectra, including the peak position, the peak area and the intra-sample heterogeneity of these measurements, and independently measured vitrinite/solid bitumen reflectance for a suite of mudstones, representing different age, geological context and burial depth. With the increased values in peak area and position, we identified an increase in the carbon mass fraction of organic matter and the mean nominal oxidation state of carbon approaching zero. These trends, which are consistent with aromatisation and graphitisation, provide the rationale for using FE-EPMA to estimate the thermal maturity of organic matter. To explore some of these trends in more detail, we employed time-of-flight secondary ionisation mass spectrometry, X-ray photoelectron spectroscopy and optical reflectance measurements on a subset of samples.

Geostandards and Geoanalytical Research↗
USGS2025

Low-sulfidation epithermal deposits of the central Basin and Range Province, USA

The Basin and Range Province is host to many important low-sulfidation epithermal deposits. Within this broad zone of extension, epithermal deposits are hosted by specific areas of Miocene and younger bimodal volcanism. In northern Nevada, rifting and related volcanic activity occurred in response to thermal bulging during the development of the Yellowstone hotspot. The Colorado River Extensional Corridor in southern Nevada, adjoining eastern California and northwestern Arizona, is a major zone of Miocene crustal extension formed during the transformation of the western margin of North America from a convergent to a transform plate boundary. The style of mineralization in the low-sulfidation epithermal deposits in these areas is strongly controlled by the nature of the volcanic successions. Highgrade, low-tonnage deposits are commonly found in flow-dominated volcanic successions where ore deposition occurred through short-lived periods of fluid flashing. In contrast, low-grade, large-tonnage deposits are more commonly located in clastic-dominated successions where fluid infiltration of the permeable hosts and cooling predominated.

Arizona, California, Nevada, Oregon↗
USGS2026

Rapid hydrothermal triggering of induced seismicity at the Coso Geothermal Field

The long-term producing Coso Geothermal Field (CGF) in California operates over 100 wells tapping into a reservoir characterized by an extensive fracture network, complex fluid pathways, and regular seismic activity. Understanding the interaction between seismicity and injection can shed important light on the hydrothermal characteristics of the field. Here, we analyze 15 years of local seismic and daily operational data from the CGF, identifying a strong correlation between short-term increase in seismicity rate and seasonal volumetric and temperature variations in the reinjected fluid. Furthermore, the seismic footprint during peak injection of colder fluids reveals a near-instantaneous response up to 2 km away from the injection well, too rapid for pore pressure diffusion alone. This short-term and distant response is observed to have directional preference, indicating structural or permeability anisotropy within the reservoir. Additionally, the seismic response correlates with the initial volumetric increase of colder fluids, but also with temperature decrease during stable injection periods, suggesting thermal effects alone can play an important role in triggering distant seismicity.

California↗
USGS2025

A high-resolution 3-D P-wave velocity structure of the south-central Cascadia subduction zone from wide-angle shore-crossing seismic refraction data

This study addresses a significant gap in understanding the features of the south-central Cascadia subduction zone, a region characterized by complex geologic, tectonic, and seismic transitions both offshore and onshore. Unlike other segments along this margin, this area lacks a 3-D velocity model to delineate its structural and geological features on a fine scale. To address this void, we developed a high-resolution 3-D P-wave velocity model using active source seismic data from ship-borne seismic shots recorded on temporary and permanent onshore seismic stations and ocean-bottom seismometers. Our model shows velocity variations across the region with distinct velocity-depth profiles for the Siletz, Franciscan, and Klamath terranes in the overlying plate. We identified seaward dipping high-velocity static backstops associated with the Siletz and Klamath terranes, situated near the shoreline and further inland, respectively. Regions of reduced crustal velocity are associated with crustal faults. Moreover, there is significant along-strike depth variation in the subducting slab, which is about 4 km deeper near the thick, dense Siletz terrane and becomes shallower near the predominantly less-dense Franciscan terrane. This highlights a sudden tectonic and geologic transition at the southern boundary of the Siletz terrane. Our velocity model also indicates slightly increased hydration, though still minimal, in both the oceanic crust and the upper mantle of the subducting plate compared to other parts of the margin.

British Columbia, California, Oregon, Washington↗
USGS2026

Treatability study to evaluate bioremediation of trichloroethene at Site K, former Twin Cities Army Ammunition Plant, Arden Hills, Minnesota, 2020–22

Executive Summary Chlorinated solvents, including trichloroethene (TCE) and other chlorinated volatile organic compounds (cVOCs), are widespread contaminants that can be treated by bioremediation approaches that enhance anaerobic reductive dechlorination. Reductive dechlorination can be enhanced either through the addition of an electron donor (biostimulation) or the addition of a known dechlorinating culture (bioaugmentation) along with an electron donor. Although bioremediation has been applied at many TCE-contaminated groundwater sites, application in source zones at sites where residual dense nonaqueous phase liquid (DNAPL) is present is more limited. In this study, laboratory and field treatability tests were completed to evaluate the potential application of anaerobic bioremediation for a shallow groundwater plume containing TCE in a perched alluvial aquifer at Site K, former Twin Cities Army Ammunition Plant, Arden Hills, Minnesota, which was on the National Priorities List as the New Brighton/Arden Hills Superfund site until 2019. In addition to the presence of residual DNAPL at the site, temporal variability in groundwater flow directions and input of oxygenated recharge were possible complicating factors for the application of enhanced anaerobic biodegradation in the shallow plume. The Site K plume extends beneath the footprint of Building 103, which was demolished in 2006, and soil excavations to a maximum depth of 6 feet (ft) below ground surface in 2014 were known to leave some deeper contaminated soil in place in the TCE source area. Groundwater treatment at the site, formalized as part of the 1997 Record of Decision, has been in operation since 1986 and consists of an extraction trench at the downgradient edge of the plume to collect groundwater, which is then pumped to an on-site air stripper. Groundwater concentrations in the plume have been relatively stable since treatment began, indicating a continued source of TCE in the aquifer. The desire for a destructive remedy that would enhance the removal of cVOCs in the aquifer at Site K and shorten the remediation timeframe led the U.S. Army to request that the U.S. Geological Survey conduct a groundwater treatability study to assess bioremediation. This report describes the U.S. Geological Survey bioremediation treatability study conducted during 2020–22, including pre-design site characterization to assist in formulating the bioremediation approach, laboratory experiments to support the design of the field pilot test, and implementation and 1-year performance monitoring results for the pilot test. Pre-design site characterization included the collection of soil cores for cVOC analysis and lithologic descriptions and the re-installment of three wells to obtain hydrologic measurements and initial groundwater chemistry. Relatively flat head gradients were measured at the site, and substantial decreases in water-level elevations occurred from spring to summer (May–July 2021). Continuous water-level monitoring indicated a rapid response to precipitation. Groundwater flow velocities were consistently less than 0.5 foot per day, and the pilot bioremediation test was therefore designed with short lateral distances (about 5 ft) between injection and individual monitoring points. Soil analyses confirmed that high volatile organic compound contamination was left in place in the source area. The highest concentrations were near or in clay at the base of the perched aquifer. Concentrations of cVOCs measured in the replaced wells were consistent with historical data and had a maximum TCE concentration of 57,700 micrograms per liter (μg/L), indicative of nearby residual DNAPL based on the general rule of observed concentrations exceeding 1 percent of solubility. The primary TCE daughter product detected was 1,2-cis-dichloroethene (cisDCE), which indicated limited reductive dechlorination in the plume. Groundwater in both the source and downgradient areas was relatively reducing during the pre-design characterization, particularly in the source area where methane concentrations greater than 400 μg/L were measured. Initial laboratory tests conducted using native aquifer microorganisms from the three replacement wells showed that anaerobic TCE biodegradation rates were low when biostimulated with the addition of sodium lactate as an electron donor, also known as a carbon donor, and resulted in the production of only cisDCE. Addition of a known dechlorinating culture, WBC-2, however, resulted in rapid biodegradation and production of ethene, verifying complete reductive dechlorination of TCE. Microcosms constructed with aquifer soil collected from the site were used to evaluate other electron donors besides lactate to support reductive dechlorination by WBC-2, including corn syrup as an alternative fast-release compound and whey, soy-based vegetable oil, and 3-D Microemulsion (Regenesis, San Clemente, California) as slow-release compounds. First-order rate constants for total organic chlorine removal in these WBC-2 amended microcosms were greatest with either lactate or vegetable oil as the donor, ranging between 0.061 and 0.047 per day or corresponding half-lives of 11–15 days. Testing of commercial products in other WBC-2-bioaugmented microcosms led to selection for the field pilot test of an emulsified vegetable oil product that also contained some sodium lactate as a fast-release donor. Delaying the addition of WBC-2 relative to the donor in the microcosms resulted in the most rapid overall biodegradation rates. The selected design for the pilot test utilized three separate test plots, each about 30-ft wide and 60-ft long: plots GS1 and GS2 in the source area of the plume and plot GS3 in the downgradient area of the plume near the excavation trench. Each test plot had one injection well, one monitoring well upgradient from the injection point, and 12 surrounding monitoring wells in a grid to capture variable groundwater flow directions. Donor injections, which included a bromide tracer, were completed in October 2021, immediately following baseline sampling, and the WBC-2 culture was injected about 40 days later, between November 30 and December 2, 2021. Performance monitoring conducted until December 2022 included hydrologic measurements and analyses of cVOCs, redox-sensitive constituents, dissolved organic carbon, bromide, volatile fatty acids, compound-specific carbon isotopes, and microbial communities. The biogeochemical data collected during the pilot tests in the three treatment plots showed that enhanced, complete reductive dechlorination of cVOCs in the groundwater was achieved in the GS1 and GS3 plots. In contrast, evidence of distribution of the injected amendments and subsequent biodegradation was limited in GS2, which was in an area of more heterogeneous soil lithology and low water table elevations. The molar composition of volatile organic compounds in the GS1 and GS3 plots was dominated by ethene in wells that were reached by the injected amendments by the end of the monitoring period. In the GS1 and GS3 plots, similar patterns were observed of cVOC concentrations decreasing to near detection levels, or below, at some wells sampled in July and October 2022, whereas ethene became dominant and indicated sustained complete reductive dechlorination. Baseline cVOC concentrations were more than a factor of 10 higher in the groundwater in the GS1 plot than in GS3, but no apparent inhibition of complete dechlorination occurred. As expected from the initial pre-design site data and the laboratory experiments, enhanced dissolution of residual DNAPL coupled to biodegradation was evident in the GS1 plot, where a marked increase in dichloroethene (DCE) above the initial baseline and upgradient TCE and DCE concentrations occurred. DCE concentrations subsequently declined where DNAPL dissolution was evident, concurrent with production of vinyl chloride and then predominantly ethene. Thus, overall biodegradation rates outpaced the DNAPL dissolution and desorption and DCE production in the source area. This success in complete degradation to predominantly ethene was achieved even in areas where the DCE concentrations reached a maximum of about 30,000 μg/L. Compound specific isotope analysis of carbon in TCE, cisDCE, trans-1,2-dichloroethene, and vinyl chloride was conducted to provide another line of evidence of the occurrence and extent of anaerobic biodegradation. Along a flow path in each plot that was affected by the injected amendments, carbon isotopes in the TCE and daughter cVOCs in the groundwater became isotopically heavier, indicating biodegradation. Enhanced biodegradation rates calculated from the field tests in GS1 and GS3 showed half-lives of 36.9–75.3 days for DCE degradation and 9.48–38.5 days for ethene production. Notably, these ethene production rates calculated from the field tests are consistent with the results of WBC-2-bioaugmented microcosms amended with either lactate or vegetable oil, which had half-lives for total organic chlorine removal that ranged from 11 to 15 days. These rates indicated rapid enhanced biodegradation, which is promising for application of a full-scale bioremediation remedy. Ultimately, however, the mass of residual or sorbed TCE in the aquifer that remains accessible for dissolution and biodegradation would likely control the time required for a full-scale bioremediation effort to achieve performance goals for TCE and cisDCE specified in the Record of Decision for Site K. The field pilot tests showed that the relatively low hydraulic head gradients and temporal changes in groundwater flow directions in the shallow aquifer would add complexity to a full-scale bioremediation effort. The radius of influence (ROI) at GS1 and GS3 (16.3 ft and 12.7 ft, respectively) were close to the design ROI of 15 ft. The estimated ROI at GS2 was about four times the design ROI, but may be less reliable at this location owing to groundwater flow direction. In addition, the low temperatures following WBC-2 injection in late November to early December 2021, in combination with the low hydraulic head gradients, were probably major factors in the delay observed before the onset of enhanced biodegradation following injection of the culture. Additional test injections could be beneficial to optimize the timing of donor and culture injections with the variable temperatures and hydraulic head in the shallow aquifer.

Minnesota↗
USGS2025

Relationship of basin structure and bedrock lithology to faulting in the 2019 Ridgecrest earthquake region, California, from gravity and aeromagnetic data

We investigate patterns of cumulative offsets on the faults that ruptured in 2019 and along the Garlock Fault in the Ridgecrest region, California using recently published gravity and aeromagnetic data. We also examine the relationship of basin structure and bedrock structure to the 2019 M7.1 Ridgecrest earthquake ruptures (Fig. 1A), which were primarily along a dextral northwest-striking fault system, and along a sinistral northeast-striking fault, which ruptured hours earlier with a M6.4 event.

California↗
USGS1998

Satellite imagery of the north-central Gulf of Mexico, June 1993-May 1997

This CD contains imagery collected by the Advanced Very High Resolution Radiometer (AVHRR) on the NOAA polar-orbiting weather satellites. The AVHRR provides almost daily coverage of a site at a resolution of approximately 1 km. The data types included are sea surface temperature (SST), water reflectance (REF), and a false-color infrared overview (FCI).

Alabama, Florida, Louisiana, Mississippi↗