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

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At least 73 records · Page 4Linked to original sources
USGS1975

Physical factors determining the fraction of stored energy recoverable from hydrothermal convection systems and conduction-dominated areas

This report contains background analyses for the estimates of Nathenson and Muffler (1975) of geothermal resources in hydrothermal convection systems and conduction-dominated areas. The first section discusses heat and fluid recharge potential of geothermal reservoirs. The second section analyzes the physical factors that determine the fraction of stored energy obtainable at the surface from a geothermal reservoir. Conversion of heat to electricity and the use of geothermal energy for direct-heating applications are discussed in the last two sections. Nathenson, Manuel, and Muffler, L.J.P., 1975, Geothermal resources in hydrothermal convection systems and conduction dominated areas, in White, D.E., and Williams, D.L., eds., Assessment of the Geothermal Resources of the United States--1975: U.S. Geological Survey Circular 726, p. 104-121, available at http://pubs.er.usgs.gov/usgspubs/cir/cir726

Open-File Report↗
USGS1955

Is Carbon dioxide an ore-forming fluid under shallow-earth conditions?

A review of some of the physical-chemical properties of CO 2 and of the system CO 2 --H 2 O indicates that under some shallow-earth conditions CO 2 can exist as a separate phase with a density approximately that of water. The effect of dissolved neutral or acid salts on the solubility of CO 2 in H 2 O is not large. Carbonates, oxides, and silicates, through reactions with a CO 2 -saturated water phase, will eventually cause the disappearance of a CO 2 phase. The prevalence of CO 2 in the earth's crust is attested by its abundance in natural gases and fluid inclusions in minerals. Some of the characteristics of uranium ores of the Colorado Plateau are not incompatible with the assumption that deposition was from a fluid CO 2 phase.

Economic Geology↗
USGS2016

Characterizing potentially induced earthquake rate changes in the Brawley Seismic Zone, southern California

The Brawley seismic zone (BSZ), in the Salton trough of southern California, has a history of earthquake swarms and geothermal energy exploitation. Some earthquake rate changes may have been induced by fluid extraction and injection activity at local geothermal fields, particularly at the North Brawley Geothermal Field (NBGF) and at the Salton Sea Geothermal Field (SSGF). We explore this issue by examining earthquake rate changes and interevent distance distributions in these fields. In Oklahoma and Arkansas, where considerable wastewater injection occurs, increases in background seismicity rate and aftershock productivity and decreases in interevent distance were indicative of fluid‐injection‐induced seismicity. Here, we test if similar changes occur that may be associated with fluid injection and extraction in geothermal areas. We use stochastic epidemic‐type aftershock sequence models to detect changes in the underlying seismogenic processes, shown by statistically significant changes in the model parameters. The most robust model changes in the SSGF roughly occur when large changes in net fluid production occur, but a similar correlation is not seen in the NBGF. Also, although both background seismicity rate and aftershock productivity increased for fluid‐injection‐induced earthquake rate changes in Oklahoma and Arkansas, the background rate increases significantly in the BSZ only, roughly corresponding with net fluid production rate increases. Moreover, in both fields the interevent spacing does not change significantly during active energy projects. This suggests that, although geothermal field activities in a tectonically active region may not significantly change the physics of earthquake interactions, earthquake rates may still be driven by fluid injection or extraction rates, particularly in the SSGF.

California↗
USGS2021

Spatial clustering of aftershocks impacts the performance of physics‐based earthquake forecasting models

I explore why physics‐based models of earthquake triggering rarely outperform statistical models in prospective testing, outside of limited spatial‐temporal windows. Pseudo‐prospective tests on suites of synthetic aftershock sequences show that a major factor is the level of unmodeled spatial clustering of the direct aftershocks triggered by the mainshock. The synthetic sequences are generated from generalized “physical” triggering models, optionally superimposed on background heterogeneity that controls the level of clustering. The statistical Epidemic Type Aftershock Sequence (ETAS) model performs relatively better the more clustered the direct aftershocks, while the true generalized “physical” model performs relatively worse. Real aftershocks appear to be sufficiently clustered to allow ETAS to perform as well as or better than physical models such as Coulomb stress triggering. A likely cause of the spatial clustering of direct aftershocks is heterogeneity of the background physical conditions, which typically is not modeled in physics‐based forecasts. This implies that the forecast performance of physical models could be substantially improved through a better understanding of the interaction between earthquake stress changes and variable background physical conditions such as stress state, fault strength, and fluid pressure.

JGR Solid Earth↗
USGS2016

High concentrations of manganese and sulfur in deposits on Murray Ridge, Endeavour Crater, Mars

Mars Reconnaissance Orbiter HiRISE images and Opportunity rover observations of the ~22 km wide Noachian age Endeavour Crater on Mars show that the rim and surrounding terrains were densely fractured during the impact crater-forming event. Fractures have also propagated upward into the overlying Burns formation sandstones. Opportunity’s observations show that the western crater rim segment, called Murray Ridge, is composed of impact breccias with basaltic compositions, as well as occasional fracture-filling calcium sulfate veins. Cook Haven, a gentle depression on Murray Ridge, and the site where Opportunity spent its sixth winter, exposes highly fractured, recessive outcrops that have relatively high concentrations of S and Cl, consistent with modest aqueous alteration. Opportunity’s rover wheels serendipitously excavated and overturned several small rocks from a Cook Haven fracture zone. Extensive measurement campaigns were conducted on two of them: Pinnacle Island and Stuart Island. These rocks have the highest concentrations of Mn and S measured to date by Opportunity and occur as a relatively bright sulfate-rich coating on basaltic rock, capped by a thin deposit of one or more dark Mn oxide phases intermixed with sulfate minerals. We infer from these unique Pinnacle Island and Stuart Island rock measurements that subsurface precipitation of sulfate-dominated coatings was followed by an interval of partial dissolution and reaction with one or more strong oxidants (e.g., O 2 ) to produce the Mn oxide mineral(s) intermixed with sulfate-rich salt coatings. In contrast to arid regions on Earth, where Mn oxides are widely incorporated into coatings on surface rocks, our results demonstrate that on Mars the most likely place to deposit and preserve Mn oxides was in fracture zones where migrating fluids intersected surface oxidants, forming precipitates shielded from subsequent physical erosion.

American Mineralogist↗
USGS2007

Time-domain electromagnetic soundings to characterize water quality within a freshwater/saline-water transition zone, Estancia Valley, New Mexico, July 2005: A reconnaissance study

During July 2005, the U.S. Geological Survey, in cooperation with the New Mexico Bureau of Geology and Mineral Resources, conducted a reconnaissance study in the Estancia Valley in central New Mexico to characterize water quality using time-domain electromagnetic (TDEM) surface-geophysical soundings. TDEM sounding is one of a number of surface geophysical methods that provide a relatively quick and inexpensive means to characterize subsurface geologic and hydrogeologic properties. TDEM surface geophysical methods can be used to detect variations in the electrical resistivity of the subsurface, which in turn can be related to variations in the physical and chemical properties of soil, rock, and pore fluids.

New Mexico↗
USGS1979

Preliminary report on drilling in and near the San Andreas fault zone, California; Dry Lake Valley No. 1

The purpose of drilling into the San Andreas fault zone is threefold. First, recovery of material from depth will permit determination of the composition and constitutive properties of both solid and fluid phases. Second, it will enable measurements of the physical state of the fault zone to be made (that is, the state of in-situ stress, pore pressure, and temperature). Finally, it will allow emplacement of instruments at depth in the fault zone as part of experiments related to earthquake prediction. This report briefly describes the drilling history and preliminary analysis of fault zone materials from site Dry Lake Valley (DLV) No. 1 (Fig. 1). The site is located at Lat. 36028.09'N, Long. 12103.32'W. This site was chosen in an attempt to drill a 1 km deep well that would reach earthquake foci. Although the entire central section of the San Andreas fault is characterized by moderate seismicity and aseismic creep, Dry Lake Valley has particularly shallow earthquakes as well as a fairly high creep rate (18-20 mm/year, S. Schultz, pers. comm.). Fig. 2 is a longitudinal section along the San Andreas fault showing high precision locations of magnitude one or greater earthquakes that occurred in 1973-1975 (from W. Ellsworth, per. comm.). The depth accuracy of the earthquakes shown is about ± 0.5 km, and it is obvious from Figure 2 that Dry Lake Valley earthquakes are extremely shallow. As shown in Figure 1 the general geology of the central section of the San Andreas fault consists of Tertiary to Jurassic sedimentary and volcanic rocks overlying Cretaceous age Gabilan granite of the Salinian Block on the west side of the fault and Cretaceous-Jurassic sedimentary assemblages of the Franciscan Complex to the east of the fault. Dibblee (1979) summarizes the geology along the central San Andreas fault. At the Dry Lake Valley site as much as 2 km of Pliocene-Miocene marine sediments (Etchegoin and Santa Margarita formation) overlie Franciscan rocks on the northeast side of the San Andreas fault. On the southwestern side of the fault, 1-2 km of Pliocene-Miocene valley sediments and granitic conglomerate overlies the Gabilan granite.

California↗
USGS1979

Preliminary analysis of clay gouge from a well in the San Andreas fault zone in central California

Drilling into the San Andreas fault zone has begun in central California as part of the U.S.G.S. program of fault zone studies. The purpose of drilling into the fault zone is threefold. First, it will allow recovery of material from depth in order to determine the composition of both solid and fluid phases. Second, it will allow determination of the physical state of the fault zone, that is, the state of stress, pore pressure, and temperature. Finally, it will allow emplacement of instruments at depth in the fault zone for monitoring experiments related to short-term earthquake prediction. In an attempt to drill to the depth of earthquake focii, the initial drill site was chosen at a locale known as Dry Lake Valley (Fig. 1). Although the entire central section of the San Andreas fault is characterized by moderate seismicity and aseismic creep, Dry Lake Valley has particularly shallow earthquakes as well as a fairly high creep rate (18-20 mm/year). Figure 2 is a longitudinal section along the San Andreas fault. The high precision earthquake locations shown are magnitude one or greater events that occurred in 1973-1975 (from W. Ellsworth, pers. comm.). The depth estimates are accurate to about + 0.5 km. It is obvious from the figure that earthquakes in the section of the fault near the well are quite shallow.

California↗
USGS2007

Downhole measurements in the AND-1B borehole, ANDRILL McMurdo Ice Shelf Project, Antarctica

A comprehensive set of downhole measurements was collected in the AND-1B drillhole as part of the on-ice scientific programme defined for the McMurdo Ice Shelf (MIS) Project. Geophysical logs were recorded over two operation phases and consisted of calliper, temperature, fluid conductivity, induction resistivity, magnetic susceptibility, natural gamma activity, acoustic televiewer, borehole deviation, and dipmeter. In addition, two standard vertical seismic profiles (VSP) and one walk-away VSP were obtained. Radioactive logs (porosity and density) were not run because of unstable borehole conditions. Although the total depth of the hole is 1285 metres below seafloor (mbsf), the depth range for in situ measurements was limited by the length of the wireline (1018 mbsf) and by the nullification of some geophysical logs due to the presence of steel casing. A depth correction was derived to account for systematic discrepancies in depth between downhole measurements and cores; consequently, log responses can be directly compared to core properties. The resulting data are amenable to studies of cyclicity and climate, heat flux and fluid flow, and stricture and stress. When integrated with physical properties and fractures measured on the core, this information should play a significant role in addressing many of the scientific objectives of the ANDRILL programme.

Terra Antarctica↗
USGS2003

Hydraulic logging methods - A summary and field demonstration in Conyers, Rockdale County, Georgia

Geophysical surveying techniques provide important information for ground-water investigations (Zohdy and others, 1974; Keys, 1997; Haeni and others, 2001). Subsurface-geophysical methods are used to delineate and characterize hydraulically active zones; the extent of contamination, and contaminant sources; identify geologic features; optimize monitoring well placement; and guide remediation efforts. Borehole-geophysical methods provide information about the physical, chemical, and hydraulic properties of rock, sediments, and fluids in the subsurface and provide important information on subsurface bedrock structures including lithology, rock fabric, location, orientation, and hydraulic properties of fractures (Keys, 1990). Effective use of geophysical data requires that the data be interpreted in the context of known local and regional geology and hydrogeology. In addition, because of the complexity and heterogeneity of crystalline-rock aquifers, a suite of borehole geophysical methods is used to determine the location, extent, and nature of fractures and other structural features in the bedrock aquifer. The geophysical data from each borehole and method are analyzed together to provide an integrated interpretation, thereby reducing the ambiguity that can occur by interpreting each geophysical log individually (Shapiro and others, 1999). Previous work using borehole geophysics to characterize ground-water availability in crystalline rock aquifers includes Chapman and Lane (1996), Mack and others (1998), and Johnson and others (1999). Other investigations that focused on contamination in fractured-rock aquifers used geophysical methods to relate highly transmissive features to structural features in the bedrock (Hansen and Lane, 1995; and Lane and others, 2002).

Georgia↗
USGS2008

In situ Raman spectroscopic investigation of the structure of subduction-zone fluids

In situ Raman spectra of synthetic subduction-zone fluids (KAlSi3O8-H2O system) were measured to 900?? and 2.3 GPa using a hydrothermal diamond-anvil cell. The structures of aqueous fluid and hydrous melt become closer when conditions approach the second critical endpoint. Almost no three-dimensional network was observed in the supercritical fluid above 2 GPa although a large amount of silicate component is dissolved, suggesting that the physical and chemical properties of these phases change drastically at around the second critical endpoint. Our experimental results indicate that the fluids released from a subducting slab change from aqueous fluid to supercritical fluid with increasing depth under the volcanic arcs. Copyright 2008 by the American Geophysical Union.

Journal of Geophysical Research B: Solid Earth↗
USGS2025

An exploration of the relative influence of physical models for Omori’s law

Omori’s law states that the rate of aftershocks decays as a function of inverse time. There are multiple physical explanations that we reduce into a nonlinear mixed effects relation of three terms: (1) a Rate/State expression that can account for static/dynamic and viscoelastic triggering caused directly by the mainshock, (2) a fluid diffusion triggering term, and (3) a randomized secondary triggering (cascade) term. We fit free physical-model parameters to an observed aftershock sequence through two nonlinear regression methods to find the relative contributions of physics-based models in an observed aftershock sequence. Results from both methods show that Rate/State models overpredict aftershock rates by ∼0–30%. Secondary aftershocks cause a net negative contribution (seismicity rate reduction that corrects overprediction by other terms) ranging between ∼0 and 30%. All regression solutions yield negative secondary triggering contributions without being guided to do so. A physical explanation for this is that aftershock occurrence relieves stress from the crust, ultimately causing the sequence to extinguish itself. Fluid diffusion triggering contributions range from ∼0 to 20%. Diffusion processes are observed to be shorter in time than the full duration of an aftershock sequence and they are also spatially limited, diminishing their influence. Our results apply to an aftershock decay curve from the 2016 Central Apennines earthquake sequence, meaning that our specific results may not be general. Our primary conclusion is that any one physical model cannot alone fit the observed sequence as well as the combination of three we investigated.

Frontiers in Earth Science↗
USGS2024

Cyclic injection leads to larger and more frequent induced earthquakes under volume-controlled conditions

As carbon storage technologies advance globally, methods to understand and mitigate induced earthquakes become increasingly important. Although the physical processes that relate increased subsurface pore pressure changes to induced earthquakes have long been known, reliable methods to forecast and control induced seismic sequences remain elusive. Suggested reservoir engineering scenarios for mitigating induced earthquakes typically involve modulation of the injection rate. Some operators have implemented periodic shutdowns (i.e., effective cycling of injection rates) to allow reservoir pressures to equilibrate (e.g., Paradox Valley) or shut‐in wells after the occurrence of an event of concern (e.g., Basel, Switzerland). Other proposed scenarios include altering injection rates, actively managing pressures through coproduction of fluids, and preinjection brine extraction. In this work, we use 3D physics‐based earthquake simulations to understand the effects of different injection scenarios on induced earthquake rates, maximum event magnitudes, and postinjection seismicity. For comparability, the modeled injection considers the same cumulative volume over the project’s operational life but varies the schedule and rates of fluid injected. Simulation results show that cyclic injection leads to more frequent and larger events than constant injection. Furthermore, with intermittent injection scenario, a significant number of events are shown to occur during pauses in injection, and the seismicity rate remains elevated for longer into the postinjection phase compared to the constant injection scenario.

Seismological Research Letters↗
USGS1981

Physical-chemical conditions of ore deposition

Ore deposits form under a wide range of physical and chemical conditions, but those precipitating from hot, aqueous fluids—i.e. the hydrothermal deposits—form generally below 700°C and at pressures of only 1 or 2 kbar or less. Natural aqueous fluids in rocks may extract metal and sulfur from a variety of rock types or may acquire them as a residual heritage from a crystallizing silicate magma. Ore-forming hydrothermal fluids never appear as hot springs (except in deep, submarine situations) because they boil, mix with surface waters, and cool, thereby losing their ore-bearing ability before reaching the surface. Mineral systems function as chemical buffers and indicators just as buffers and indicators function in a chemical laboratory. By reading the record written in the buffer/indicator assemblages of minerals one can reconstruct many aspects of the former chemical environment. By studying the record of changing conditions one may deduce information regarding the processes functioning to create the succession of chemical environments and the ore deposits they represent. The example of the OH vein at Creede, Colorado, shows a pH buffered by the K-feldspar + muscovite + quartz assemblage and the covariation of S 2 and O 2 buffered by the assemblage chlorite + pyrite + quartz. Boiling of the ore fluid led to its oxidation to hematite-bearing assemblages and simultaneously produced an intensely altered, sericitic capping over the vein in response to the condensation of vapors bearing acidic components. The solubility of metals as calculated from experimental and theoretical studies of mineral solubility appears too low by at least one or two powers of ten to explain the mineralization at Creede. In contrast to Creede where the mineral stabilities all point to a relatively consistent chemistry, the Mississippi Valley type deposits present a puzzle of conflicting chemical clues that are impossible to reconcile with any single equilibrium situation. Thus we must seriously consider metastable equilibria; those most likely involve redox disequilibrium among the sulfur species in solution and perhaps also involve organic compounds.

Physics and Chemistry of the Earth↗
USGS2008

Implications of rate-limited mass transfer for aquifer storage and recovery

Pressure to decrease reliance on surface water storage has led to increased interest in aquifer storage and recovery (ASR) systems. Recovery efficiency, which is the ratio of the volume of recovered water that meets a predefined standard to total volume of injected fluid, is a common criterion of ASR viability. Recovery efficiency can be degraded by a number of physical and geochemical processes, including rate-limited mass transfer (RLMT), which describes the exchange of solutes between mobile and immobile pore fluids. RLMT may control transport behavior that cannot be explained by advection and dispersion. We present data from a pilot-scale ASR study in Charleston, South Carolina, and develop a three-dimensional finite-difference model to evaluate the impact of RLMT processes on ASR efficiency. The modeling shows that RLMT can explain a rebound in salinity during fresh water storage in a brackish aquifer. Multicycle model results show low efficiencies over one to three ASR cycles due to RLMT degrading water quality during storage; efficiencies can evolve and improve markedly, however, over multiple cycles, even exceeding efficiencies generated by advection-dispersion only models. For an idealized ASR model where RLMT is active, our simulations show a discrete range of diffusive length scales over which the viability of ASR schemes in brackish aquifers would be hindered.

Groundwater↗
USGS2022

Electrical imaging for hydrogeology

Geophysical methods offer hydrogeologists unprecedented access to understanding subsurface parameters and processes. In this book, we outline the theory and application of electrical imaging methods, which inject current into the ground and measure the resultant potentials. These data are sensitive to rock type, grain size, porosity, pore fluid electrical conductivity, saturation, and temperature. Here, we describe the physical basis for electrical imaging, parallels between electrical flow equations and the groundwater flow equation, practical considerations for field investigations, data processing and inverse modeling of field data, and how to QA/QC data. We additionally cover two case studies, including a 2-D waterborne survey and a 4-D dataset from a biostimulation experiment.

Book↗
USGS2007

Physical and chemical controls on the critical zone

Geochemists have long recognized a correlation between rates of physical denudation and chemical weathering. What underlies this correlation? The Critical Zone can be considered as a feed-through reactor. Downward advance of the weathering front brings unweathered rock into the reactor. Fluids are supplied through precipitation. The reactor is stirred at the top by biological and physical processes. The balance between advance of the weathering front by mechanical and chemical processes and mass loss by denudation fixes the thickness of the Critical Zone reactor. The internal structure of this reactor is controlled by physical processes that create surface area, determine flow paths, and set the residence time of material in the Critical Zone. All of these impact chemical weathering flux.

Elements↗
USGS2013

Stress, deformation, conservation, and rheology: a survey of key concepts in continuum mechanics

This chapter provides a brief survey of key concepts in continuum mechanics. It focuses on the fundamental physical concepts that underlie derivations of the mathematical formulations of stress, strain, hydraulic head, pore-fluid pressure, and conservation equations. It then shows how stresses are linked to strain and rates of distortion through some special cases of idealized material behaviors. The goal is to equip the reader with a physical understanding of key mathematical formulations that anchor continuum mechanics in order to better understand theoretical studies published in geomorphology.

Book chapter↗