USGS Science⌕ Search

SEARCH · USGS Science

Results for “Advances in Geophysics”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
USGS1984

A review of crust and upper mantle structure studies of the Snake River Plain-Yellowstone volcanic system: A major lithospheric anomaly in the western U.S.A.

The Snake River Plain-Yellowstone volcanic system is one of the largest, basaltic, volcanic field in the world. Here, there is clear evidence for northeasterly progression of rhyolitic volcanism with its present position in Yellowstone. Many theories have been advanced for the origin of the Snake River Plain-Yellowstone system. Yellowstone and Eastern Snake River Plain have been studied intensively using various geophysical techniques. Some sparse geophysical data are available for the Western Snake River Plain as well. Teleseismic data show the presence of a large anomalous body with low P- and S-wave velocities in the crust and upper mantle under the Yellowstone caldera. A similar body in which compressional wave velocity is lower than in the surrounding rock is present under the Eastern Snake River Plain. No data on upper mantle anomalies are available for the Western Snake River Plain. Detailed seismic refraction data for the Eastern Snake River Plain show strong lateral heterogeneities and suggest thinning of the granitic crust from below by mafic intrusion. Available data for the Western Snake River Plain also show similar thinning of the upper crust and its replacement by mafic material. The seismic refraction results in Yellowstone show no evidence of the low-velocity anomalies in the lower crust suggested by teleseismic P-delay data and interpreted as due to extensive partial melting. However, the seismic refraction models indicate lower-than-normal velocities and strong lateral inhomogeneities in the upper crust. Particularly obvious in the refraction data are two regions of very low seismic velocities near the Mallard Eake and Sour Creek resurgent domes in the Yellowstone caldera. The low-velocity body near the Sour Creek resurgent dome is interpreted as partially molten rock. Together with other geophysical and thermal data, the seismic results indicate that a sub-lithospheric thermal anomaly is responsible for the time-progressive volcanism along the Eastern Snake River Plain. However, the exact mechanism responsible for the volcanism and details of magma storage and migration are not yet fully understood.

California, Idaho, Montana, Nevada, Oregon, Washin↗
USGS2001

The failure of earthquake failure models

In this study I show that simple heuristic models and numerical calculations suggest that an entire class of commonly invoked models of earthquake failure processes cannot explain triggering of seismicity by transient or "dynamic" stress changes, such as stress changes associated with passing seismic waves. The models of this class have the common feature that the physical property characterizing failure increases at an accelerating rate when a fault is loaded (stressed) at a constant rate. Examples include models that invoke rate state friction or subcritical crack growth, in which the properties characterizing failure are slip or crack length, respectively. Failure occurs when the rate at which these grow accelerates to values exceeding some critical threshold. These accelerating failure models do not predict the finite durations of dynamically triggered earthquake sequences (e.g., at aftershock or remote distances). Some of the failure models belonging to this class have been used to explain static stress triggering of aftershocks. This may imply that the physical processes underlying dynamic triggering differs or that currently applied models of static triggering require modification. If the former is the case, we might appeal to physical mechanisms relying on oscillatory deformations such as compaction of saturated fault gouge leading to pore pressure increase, or cyclic fatigue. However, if dynamic and static triggering mechanisms differ, one still needs to ask why static triggering models that neglect these dynamic mechanisms appear to explain many observations. If the static and dynamic triggering mechanisms are the same, perhaps assumptions about accelerating failure and/or that triggering advances the failure times of a population of inevitable earthquakes are incorrect.

Journal of Geophysical Research B: Solid Earth↗
USGS2020

Kinematic rupture and 3D wave propagation simulations of the 2019 Mw 7.1 Ridgecrest, California, earthquake

We model the kinematic rupture process of the 2019 M w "> M w Mw 7.1 Ridgecrest, California, earthquake using numerical simulations to reproduce the elastodynamic wave field observed by inertial seismometers, high‐rate Global Navigation Satellite System stations, and borehole strainmeters. This was the largest earthquake in Southern California in 20 yr and was widely felt throughout the region. The M w "> M w Mw 7.1 mainshock was part of a large sequence of ∼ 30 , 000 "> ∼ 30 , 000 ∼30,000 aftershocks and was notably preceded by an M w "> M w Mw 6.4 foreshock by 34 hr on fault structures that were once poorly understood. A large number of seismic and geodetic instruments measured the rupture process for both events, with many stations located in the near field. Hence, this is a rare opportunity to better understand complex earthquake processes that arise in an immature fault zone using advanced computing. Of the kinematic rupture models that we tested, our preferred is the simplest one that reproduces signals recorded by the three different geophysical datasets; it is composed of four distinct ruptures that progressively migrate to the southeast with delayed initiation times, and typical rupture speeds. This type of model does a better job at matching the recorded ground motions and deformations than does one composed of a continuous rupture with very low‐rupture velocity, as proposed in other studies of this earthquake.

California↗
USGS2007

Topobathymetric data for Tampa Bay, Florida

Topobathymetric data (“topobathy”) are a merged rendering of both topography (land elevation) and bathymetry (water depth) to provide a single product useful for inundation mapping and a variety of other applications. These data were developed using one topographic and two bathymetric datasets collected at different dates. Topography was obtained from the U.S. Geological Survey's (USGS) National Elevation Dataset (NED). Bathymetry was provided by NOAA's GEOphysical DAta System (GEODAS). For several nearshore areas within the bay GEODAS data were replaced with high resolution bathymetry acquired by NASA's Experimental Advanced Airborne Research Lidar (EAARL).

Florida↗
USGS2008

Geophysical characterization of the American River levees, Sacramento, California, with electromagnetics, capacitively coupled resistivity, and DC resistivity

A geophysical characterization of a portion of American River levees in Sacramento, California was conducted in May, 2007. Targets of interest included the distribution and thickness of sand lenses that underlie the levees and the depth to a clay unit that underlies the sand. The concern is that the erosion of these sand lenses can lead to levee failure in highly populated areas of Sacramento. DC resistivity (Geometric’s OhmMapper and Advanced Geosciences, Inc.’s SuperSting R8 systems) and electromagnetic surveys (Geophex’s GEM-2) were conducted over a 6 mile length of the levee on roads and bicycle and horse trails. 2-D inversions were conducted on all the geophysical data. The OhmMapper and SuperSting surveys produced consistent inversion results that delineated potential sand and clay units. GEM-2 apparent resistivity data were consistent with the DC inversion results. However, the GEM-2 data could not be inverted due to low electromagnetic response levels, high ambient electromagnetic noise, and large system drifts. While this would not be as large a problem in conductive terrains, it is a problem for a small induction number electromagnetic profiling system such as the GEM-2 in a resistive terrain (the sand lenses). An integrated interpretation of the geophysical data acquired in this investigation is presented in this report that includes delineation of those areas consisting of predominantly sand and those areas consisting predominantly of clay. In general, along most of this part of the American River levee system, sand lenses are located closest to the river and clay deposits are located further away from the river. The interpreted thicknesses of the detected sand deposits are variable and range from 10 ft up to 60 ft. Thus, despite issues with the GEM-2 inversion, this geophysical investigation successfully delineated sand lenses and clay deposits along the American River levee system and the approximate depths to underlying clay zones. The results of this geophysical investigation should help the USACE to maintain the current levee system while also assisting the designers and planners of levee enhancements with the knowledge of what is to be expected from the near-surface geology and where zones of concern may be located.

California↗
USGS2012

USGS advances in integrated, high-resolution sea-floor mapping: inner continental shelf to estuaries

The U.S. Geological Survey (USGS) has been involved in geological mapping of the sea floor for the past thirty years. Early geophysical and acoustic mapping efforts using GLORIA (Geologic LOng Range Inclined ASDIC) a long-range sidescan-sonar system, provided broad-scale imagery of deep waters within the U.S. Exclusive Economic Zone (EEZ). In the early 1990's, research emphasis shifted from deep- to shallow-water environments to address pertinent coastal research and resource management issues. Use of shallow-water, high-resolution geophysical systems has enhanced our understanding of the processes shaping shallow marine environments. However, research within these shallow-water environments continues to present technological challenges.

Conference Paper↗
USGS2011

Exploring geophysical processes influencing U.S. West Coast precipitation and water supply

CalWater Science Workshop; La Jolla, California, 8-10 June 2011 CalWater is a multiyear, multiagency research project with two primary research themes: the effects of changing climate on atmospheric rivers (ARs) and associated extreme events, and the potential role of aerosols in modulating cloud properties and precipitation, especially regarding orographic precipitation and water supply. Advances made in CalWater have implications for both water supply and flood control in California and other West Coast areas, both in the near term and in a changing climate.

Eos, Transactions, American Geophysical Union↗
USGS2014

Part I—History and activities of the section of geophysics of the United States Geological Survey

From the beginning of time, all ingenuity of mankind has been concentrated upon the methods of finding gold and unusual deposits in the earth. An illustration (Fig. 1) from the old treatise by Agricola, “De Re Metallica,” published in 1580, will serve to show the implicit faith of that generation in divining methods. However, it was not until 1920 that real progress was made in prospecting by using the latest advances of the physical sciences. The public interest was stimulated by the successes of these methods on the part of commercial operators, and governmental agencies received many requests for information concerning their reliability. There were also, in the late 1920's, high‐pressure mine‐promotion schemes which used geophysical methods in a very questionable manner, symbolized in Figure 2 as of 1928 by an electrified forked stick. Authoritative information concerning such practices for public protection was needed to curb such notorious undertakings. Dr. Scott Turner, then Director of the United States Bureau of Mines, thoroughly understood the situation and was first in the governmental departments to recognize the possible value of a study of modern prospecting methods. The Bureau of Mines began this investigation by employing Drs. A. S. Eve and D. A. Keys of McGill University for short periods in the summer in 1927. Their first publication [see 1 of “References” at end of paper] served to illustrate the fundamental scientific principles which underlie geophysical prospecting. This was followed by a second publication [2] giving the results of field‐tests. In the light of the rapid improvements during the intervening ten years, these two papers take a historical position.

Eos, Transactions, American Geophysical Union↗
USGS2011

Active aeolian processes on Mars: A regional study in Arabia and Meridiani Terrae

We present evidence of widespread aeolian activity in the Arabia Terra/Meridiani region (Mars), where different kinds of aeolian modifications have been detected and classified. Passing from the regional to the local scale, we describe one particular dune field in Meridiani Planum, where two ripple populations are distinguished by means of different migration rates. Moreover, a consistent change in the ripple pattern is accompanied by significant dune advancement (between 0.4–1 meter in one Martian year) that is locally triggered by large avalanche features. This suggests that dune advancement may be common throughout the Martian tropics.

Geophysical Research Letters↗
USGS1997

Multispectral thermal infrared mapping of sulfur dioxide plumes: A case study from the East Rift Zone of Kilauea Volcano, Hawaii

The synoptic perspective and rapid mode of data acquisition provided by remote sensing are well suited for the study of volcanic SO 2 plumes. In this paper we describe a plume-mapping procedure that is based on image data acquired with NASA's airborne thermal infrared multispectral scanner (TIMS) and apply the procedure to TIMS data collected over the East Rift Zone of Kilauea Volcano, Hawaii, on September 30, 1988. These image data covered the Pu‘u ‘O ‘o and Kupaianaha vents and a skylight in the lava tube that was draining the Kupaianaha lava pond. Our estimate of the SO 2 emission rate from Pu‘u ‘O ‘o (17–20 kg s −1 ) is roughly twice the average of estimates derived from correlation spectrometer (COSPEC) measurements collected 10 days prior to the TIMS overflight (10 kg s −1 ). The agreement between the TIMS and COSPEC results improves when we compare SO 2 burden estimates, which are relatively independent of wind speed. We demonstrate the feasibility of mapping Pu‘u ‘O ‘o - scale SO 2 plumes from space in anticipation of the 1998 launch of the advanced spaceborne thermal emission and reflectance radiometer (ASTER).

Journal of Geophysical Research B: Solid Earth↗
USGS2014

Appendix D—Notes on Darcy's law and permeability

In any effort to establish nomenclature relating to the flow of fluids through porous media it would seem well first to consider the history of the development of our concepts and of the terms or expressions involved. Only in this way can precedent rightfully be honored and at the same time duplicating expressions be eliminated and the remaining more useful terms clarified. Then, proceeding with a foresight lined up with recent advances, we may hope to anticipate the needs of the future.

Eos, Transactions, American Geophysical Union↗
USGS2026

Opportunities and challenges for incorporating lithium-ion batteries into geophysical power systems

Batteries play a critical role at seismic and other geophysical stations in ensuring that the equipment receives uninterrupted power to make continuous observations of the Earth. Often sited in remote environments under a wide range of environmental conditions, these stations have almost ubiquitously used conventional lead‐acid batteries. However, recent advances in rechargeable lithium‐ion battery technology have led to the development of lithium‐iron phosphate (LFP) batteries that can replace lead‐acid batteries in energy storage systems. In the past three years, LFP battery production has grown over an order of magnitude, reducing their cost and increasing their availability. In this article, we examine the benefits and challenges associated with incorporating several types of LFP batteries into the power systems of geophysical stations. We review how fundamental differences in battery chemistry enable LFP batteries to weigh less than half of comparable lead‐acid batteries and may have longer service lives but have the added complexity of being managed by an integrated battery monitoring system (BMS) microcontroller. Through a controlled heat chamber experiment, we demonstrate that LFP batteries can be ideally suited for use in high‐temperature environments by offering longer service lives than lead‐acid batteries. However, for safety reasons, the BMS prevents most LFP batteries from being charged at temperatures <0°C, which complicates their use in colder regions and can lead to equipment damage if the charging system is not appropriately designed for this battery type. Finally, we address some of the unique challenges associated with adopting lithium batteries, including unexpected substantial (≤14 W) power consumption from the BMS, safety concerns, and shipping restrictions. It is our goal to help inform station operators and geophysicists about potential benefits and issues that can arise from using LFP batteries at seismic and geophysical stations in a range of environments.

Seismological Research Letters↗
USGS2010

Rheology of the lithosphere

During the quadrennial term 1979–1982, major advances have been made in our knowledge of the rheology of the oceanic lithosphere by the skillful combination of experimental and theoretical rock mechanics, seismology and marine geophysics in increasingly sophisticated models for the flexure of the oceanic lithosphere at seamounts and island chains, along transform faults, and at subduction zones. The relative simplicity of plate bending geometry, thermal history, and mineralogical and chemical compositions of the oceanic plates in these settings make the geophysical observations very powerful constraints on the in situ rheology of the oceanic lithosphere. In the first part of this paper, I review the laboratory work on materials appropriate to the oceanic lithosphere with emphasis on contributions during the quadrennial period and the need for future work. The important results of flexure models incorporating realistic material properties are then summarized.

Reviews of Geophysics and Space Physics↗
USGS2007

Ground-water recharge in the arid and semiarid southwestern United States

Ground-water recharge in the arid and semiarid southwestern United States results from the complex interplay of climate, geology, and vegetation across widely ranging spatial and temporal scales. Present-day recharge tends to be narrowly focused in time and space. Widespread water-table declines accompanied agricultural development during the twentieth century, demonstrating that sustainable ground-water supplies are not guaranteed when part of the extracted resource represents paleorecharge. Climatic controls on ground-water recharge range from seasonal cycles of summer monsoonal and winter frontal storms to multimillennial cycles of glacial and interglacial periods. Precipitation patterns reflect global-scale interactions among the oceans, atmosphere, and continents. Large-scale climatic influences associated with El Niño and Pacific Decadal Oscillations strongly, but irregularly, control weather in the study area, so that year-to-year variations in precipitation and ground-water recharge are large and difficult to predict. Proxy data indicate geologically recent periods of naturally occurring multidecadal droughts unlike any in the modern instrumental record. Any anthropogenically induced climate change will likely reduce ground-water recharge through diminished snowpack at higher elevations. Future changes in El Niño and monsoonal patterns, both crucial to precipitation in the study area, are highly uncertain in current models. Current land-use modifications influence ground-water recharge through vegetation, irrigation, and impermeable area. High mountain ranges bounding the study area—the San Bernadino Mountains and Sierra Nevada to the west, and the Wasatch and southern Colorado Rocky Mountains to the east—provide external geologic controls on ground-water recharge. Internal geologic controls stem from tectonic processes that led to numerous, variably connected alluvial-filled basins, exposure of extensive Paleozoic aquifers in mountainous recharge areas, and distinct modes of recharge in the Colorado Plateau and Basin and Range subregions. The chapters in this professional paper present (first) an overview of climatic and hydrogeologic framework (chapter A), followed by a regional analysis of ground-water recharge across the entire study area (chapter B). These are followed by an overview of site-specific case studies representing different subareas of the geographically diverse arid and semiarid southwestern United States (chapter C); the case studies themselves follow in chapters D–K. The regional analysis includes detailed hydrologic modeling within the framework of a high-resolution geographic-information system (GIS). Results from the regional analysis are used to explore both the distribution of ground-water recharge for mean climatic conditions as well as the influence of two climatic patterns—the El Niño-Southern Oscillation and Pacific Decadal Oscillation—that impart a high degree of variability to the hydrologic cycle. Individual case studies employ a variety of geophysical and geochemical techniques to investigate recharge processes and relate the processes to local geologic and climatic conditions. All of the case studies made use of naturally occurring tracers to quantify recharge. Thermal and geophysical techniques that were developed in the course of the studies are presented in appendices. The quantification of ground-water recharge in arid settings is inherently difficult due to the generally low amount of recharge, its spatially and temporally spotty nature, and the absence of techniques for directly measuring fluxes entering the saturated zone from the unsaturated zone. Deep water tables in arid alluvial basins correspond to thick unsaturated zones that produce up to millennial time lags between changes in hydrologic conditions at the land surface and subsequent changes in recharge to underlying ground water. Recent advances in physical, chemical, isotopic, and modeling techniques have fostered new types of recharge assessments. Chemical and isotopic techniques include an increasing variety of environmental tracers that are useful and robust. Physically based techniques include the use of heat as a tracer and computationally intensive geophysical imaging tools for characterizing hydrologic conditions in the unsaturated zone. Modeling-based techniques include spatially distributed water-budget computations using high-resolution remotely sensed and ground-based geographic data. Application of these techniques to arid and semiarid settings in the southwestern United States reveals distinct patterns of recharge corresponding to geologic setting, climatic and vegetative history, and land use. Analysis of recharge patterns shows that large expanses of alluvial basin floors are drying out under current climatic conditions, with little to no recharge to underlying ground water. Ground-water recharge occurs mainly beneath upland catchments in which thin soils overlie permeable bedrock, ephemeral channels in which flow may average only several hours per year, and active agricultural areas. The chapters in this professional paper represent a coordinated attempt to develop a better understanding of one of the Nation's most critical yet difficult-to-quantify renewable resources.

Professional Paper↗
USGS2014

Gravity, magnetic, and radiometric data for Newberry Volcano, Oregon, and vicinity

Newberry Volcano in central Oregon is a 3,100-square-kilometer (1,200-square-mile) shield-shaped composite volcano, occupying a location east of the main north-south trend of the High Cascades volcanoes and forming a transition between the High Lava Plains subprovince of the Basin and Range Province to the east and the Cascade Range to the west. Magnetic, gravity, and radiometric data have been gathered and assessed for the region around the volcano. These data have widely varying quality and resolution, even within a given dataset, and these limitations are evaluated and described in this release. Publicly available gravity data in general are too sparse to permit detailed modeling except along a few roads with high-density coverage. Likewise, magnetic data are also unsuitable for all but very local modeling, primarily because available data consist of a patchwork of datasets with widely varying line-spacing. Gravity data show only the broadest correlation with mapped geology, whereas magnetic data show moderate correlation with features only in the vicinity of Newberry Caldera. At large scales, magnetic data correlate poorly with both geologic mapping and gravity data. These poor correlations are largely due to the different sensing depths of the two potential fields methods, which respond to physical properties deeper than the surficial geology. Magnetic data derive from rocks no deeper than the Curie-point isotherm depth (10 to 15 kilometers, km, maximum), whereas gravity data reflect density-contrasts to 100 to 150 km depths. Radiometric data from the National Uranium Resource Evaluation (NURE) surveys of the 1980s have perhaps the coarsest line-spacing of all (as much as 10 km between lines) and are extremely “noisy” for several reasons inherent to this kind of data. Despite its shallow-sensing character, only a few larger anomalies in the NURE data correlate well with geologic mapping. The purpose of this data series release is to collect and place the available geophysical data in the hands of other investigators in a readily comprehensible form. All data-compilation, splicing, filtering, and overlay-map displays were accomplished with the commercial Geosoft™ system, Advanced Option. Images are provided in both JPG and PDF formats.

Oregon↗
USGS2018

Using stereo satellite imagery to account for ablation, entrainment, and compaction in volume calculations for rock avalanches on Glaciers: Application to the 2016 Lamplugh Rock Avalanche in Glacier Bay National Park, Alaska

The use of preevent and postevent digital elevation models (DEMs) to estimate the volume of rock avalanches on glaciers is complicated by ablation of ice before and after the rock avalanche, scour of material during rock avalanche emplacement, and postevent ablation and compaction of the rock avalanche deposit. We present a model to account for these processes in volume estimates of rock avalanches on glaciers. We applied our model by calculating the volume of the 28 June 2016 Lamplugh rock avalanche in Glacier Bay National Park, Alaska. We derived preevent and postevent 2‐m resolution DEMs from WorldView satellite stereo imagery. Using data from DEM differencing, we reconstructed the rock avalanche and adjacent surfaces at the time of occurrence by accounting for elevation changes due to ablation and scour of the ice surface, and postevent deposit changes. We accounted for uncertainties in our DEMs through precise coregistration and an assessment of relative elevation accuracy in bedrock control areas. The rock avalanche initially displaced 51.7 ± 1.5 Mm3 of intact rock and then scoured and entrained 13.2 ± 2.2 Mm3 of snow and ice during emplacement. We calculated the total deposit volume to be 69.9 ± 7.9 Mm3. Volume estimates that did not account for topographic changes due to ablation, scour, and compaction underestimated the deposit volume by 31.0–46.8 Mm3. Our model provides an improved framework for estimating uncertainties affecting rock avalanche volume measurements in glacial environments. These improvements can contribute to advances in the understanding of rock avalanche hazards and dynamics.

Alaska↗
USGS2008

Advances and limitations of individual-based models to analyze and predict dynamics of mangrove forests: A review

Mangrove ecosystems are considered vulnerable to climate change as coastal development limits the ecosystem services and adaptations important to their survival. Although they appear rather simple in terms of species diversity, their ecology is complex due to interacting geophysical forces of tides, surface runoff, river and groundwater discharge, waves, and constituents of sediment, nutrients and saltwater. These interactions limit developing a comprehensive framework for science-based sustainable management practices. A suite of models have been developed independently by various academic and government institutions worldwide to understand the dynamics of mangrove ecosystems and to provide ecological forecasting capabilities under different management scenarios and natural disturbance regimes. The models have progressed from statistical tables representing growth and yield to more sophisticated models describing various system components and processes. Among these models are three individual-based models (IBMs) (FORMAN, KIWI, and MANGRO). A comparison of models’ designs reveal differences in the details of process description, particularly, regarding neighbor competition among trees. Each model has thus its specific range of applications. Whereas FORMAN and KIWI are most suitable to address mangrove forest dynamics of stands, MANGRO focuses on landscape dynamics on larger spatial scale. A comparison of the models and a comparison of the models with empirical knowledge further reveal the general needs for further field and validation studies to advance our ecological understanding and management of mangrove wetlands.

Aquatic Botany↗