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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 163 records · Page 9Linked to original sources
USGS1988

Geologic characterization of seismic sources: Moving into the 1990s

The objective of this paper is to discuss leading-edge directions in paleoseismology and seismic geology, particularly as they relate to characterizing seismic sources. The paper builds on earlier articles that discuss some of these trends (Schwartz and Coppersmith, 1986; Schwartz, 1987). There are several areas that appear to be especially important. These are: fault segmentation, which provides a physical framework for evaluating both the size and potential location of future earthquakes on a fault zone; earthquake recurrence models, which provide information on the frequency of different size earthquakes on a fault; and long-term earthquake potential, an area in which significant advances have been made through development of earthquake hazard models that use probabilistic methodology to incorporate the uncertainties in seismic source characterization and the evolving understanding of the earthquake process.

Conference Paper↗
USGS2014

Environmental DNA calibration study. Interim technical review report

Invasive aquatic nuisance species pose a major threat to aquatic ecosystems worldwide. Invasive Asian carps, including bighead carp (Hypophthalmichthys nobilis) and silver carp (H. molitrix) have been steadily dispersing upstream through the Mississippi, Illinois, and Des Plaines Rivers since the 1990s. To prevent further movement up the Illinois River into the Chicago Area Waterway System (CAWS, see Figures 1.1.1 to 1.1.3) and possibly Lake Michigan and the Great Lakes ecosystem, an electrical barrier has been operating near Lockport to deter the advance of Asian carp. Although one adult individual has been detected in Lockport pool of the Illinois Waterway, the leading edge of the invasion of bighead and silver carp is considered to be at RM 281.5 in Dresden Island Pool, 15 miles downstream from the barrier and 55 miles from Lake Michigan, and that front has not progressed upstream since 2006. Although spawning activity has been observed in Marseilles pool in 2012, verified capture of eggs and larvae remain downstream in Peoria pool, over 140 miles from Lake Michigan (Figure 1.1.1). Should a sustainable Asian carp population become established in the Great Lakes, native fish populations, as well as many threatened or endangered plant/animal species populations, could be impacted. In response to this threat, the Asian Carp Regional Control Committee (ACRCC) was formed in part to coordinate efforts to understand and organize against the Asian carp threat. The Asian Carp Control Strategy Framework (2012a) outlined major tasks to be completed for a better understanding of factors related to the advance of Asian carp populations towards the Great Lakes. In addition, the ACRCC formed the Monitoring and Rapid Response Workgroup to address Asian carp monitoring and removal (ACRCC 2012b).

Midwest waterways↗
USGS2015

The influence of Tamarix ramosissima defoliation on population movements of the northern tamarisk beetle ( Diorhabda carinulata ) within the Colorado Plateau: Chapter 18

The northern tamarisk beetle ( Diorhabda carinulata ) was introduced to the Colorado Plateau within the Colorado River Basin in 2004, in an effort to control invasive/exotic tamarisk ( Tamarix ramosissima ) plants. Since release, there has been rapid beetle colonization and subsequent defoliation of tamarisk along the Colorado River corridor. We collected plant phenology and beetle abundance data from the Dolores and San Juan rivers, two major tributaries of the Colorado River, to document tamarisk defoliation and beetle movement patterns. We found D. carinulata population movement patterns to be highly influenced by the availability of food resources, with local beetle boom and bust events appearing common. Beetles were able to defoliate from 35-65 km of river corridor tamarisk habitat each year. Following intensive tamarisk defoliation of large riparian reaches, beetles displayed a pattern of temporary abandonment in the following year with recolonization of that habitat in the subsequent year. Larvae were found primarily in areas that had partial defoliation, while adults occurred throughout the river corridor but most often on the leading edge of defoliated habitats. Understanding this type of beetle behavior and movement patterns will be useful in the management of areas where D. carinulata has been established, and in areas where it has not yet colonized. This will also assist land managers to further understand how defoliation and the presence of D. carinulata influence tamarisk-dominated habitats within Colorado Plateau riparian ecosystems.

Dolores River, San Juan River↗
USGS1973

The concept of growth and maturity of ore-stage pyrite in roll-type uranium deposts

Roll-type uranium deposits contain both ore-stage pyrite and preore or diagenetic pyrite that was present in the host rock before the deposits began to form. Ore-stage pyrite forms as the result of redistribution and accretion from the preore pyrite. Accretion of the ore-stage pyrite seems to be governed by natural laws that limit its concentration to only a few times the concentration of the preore pyrite. Accumulations of ore-stage pyrite build up along the leading edge of a supergene oxidation zone which spreads through the host rocks, literally pushing the ore deposits ahead of it. The ore-stage pyrite probably progresses much as a wave that first grows to a nearly fixed amplitude and thereafter is steadily maintained as the mature deposit continues to advance.

Journal of Research of the U.S. Geological Survey↗
USGS1979

Decollement in the southern Allegheny Plateau of Pennsylvania

Recent field investigations in the Allegheny Plateau north of Williamsport, Pennsylvania have shown the presence of both southward dipping, low-angle thrust faults translated to the north and northward dipping back or antithectic thrusts translated to the south at the leading (north) edge of Barclay syncline. The presence of these thrusts, along with reported anomalous dips along the leading edge of the next syncline to the south (the Bernice or Barbours syncline) may indicate that the Allegheny Plateau of Pennsylvania is underlain by master decollement and that this decollement gives rise to a series of splay thrusts. In some cases such as the Barclay syncline, the combination of these forward and back thrust faults may serve as fracture porosity traps.

Open-File Report↗
USGS2018

Poroelastic stress changes associated with primary oil production in the Los Angeles Basin, California

While recent investigations of induced earthquakes have focused on earthquakes associated with wastewater injection and unconventional recovery methods, the potential for earthquakes to be induced by primary production has long been recognized. We use boundary element methods to quantify the predicted geometry and amplitude of stress and strain changes associated with removal of large volumes of fluids in poroelastic reservoirs, focusing on the Los Angeles Basin (LA Basin) in California. We show that significant stress perturbations (upward of 0.1 MPa), while localized, typically extended several kilometers away from production horizons by the early 1940s. By this time, production horizons in the southwestern LA Basin were 2–4 km deep; models thus predict that stress conditions would have been perturbed significantly on faults at the upper edge of the seismogenic brittle crust, typically around 6 km. Predicted stress and strain changes associated with oil fields in the southwestern LA Basin during the first half of the 20th century, combined with stress changes caused by the 1933 Long Beach earthquake, could plausibly have induced a number of moderate-to-large earthquakes between 1932 and 1944. The rate of earthquakes in the southwestern LA Basin has been significantly lower since 1945 than it was for the three decades prior to 1945. We conclude that while decreasing production and pore-pressure reduction contributed to the initial decline, the continued decline was due in part to the advent of widespread water-flooding methods that maintained subsurface reservoir pressures.

California↗
USGS2021

The influence of subcolony-scale nesting habitat on the reproductive success of Adélie penguins

Group-size variation is common in colonially breeding species, including seabirds, whose breeding colonies can vary in size by several orders of magnitude. Seabirds are some of the most threatened marine taxa and understanding the drivers of colony size variation is more important than ever. Reproductive success is an important demographic parameter that can impact colony size, and it varies in association with a number of factors, including nesting habitat quality. Within colonies, seabirds often aggregate into distinct groups or subcolonies that may vary in quality. We used data from two colonies of Adélie penguins 73 km apart on Ross Island, Antarctica, one large and one small to investigate (1) How subcolony habitat characteristics influence reproductive success and (2) How these relationships differ at a small (Cape Royds) and large (Cape Crozier) colony with different terrain characteristics. Subcolonies were characterized using terrain attributes (elevation, slope aspect, slope steepness, wind shelter, flow accumulation), as well group characteristics (area/size, perimeter-to-area ratio, and proximity to nest predators). Reproductive success was higher and less variable at the larger colony while subcolony characteristics explained more of the variance in reproductive success at the small colony. The most important variable influencing subcolony quality at both colonies was perimeter-to-area ratio, likely reflecting the importance of nest predation by south polar skuas along subcolony edges. The small colony contained a higher proportion of edge nests thus higher potential impact from skua nest predation. Stochastic environmental events may facilitate smaller colonies becoming “trapped” by nest predation: a rapid decline in the number of breeding individuals may increase the proportion of edge nests, leading to higher relative nest predation and hindering population recovery. Several terrain covariates were retained in the final models but which variables, the shapes of the relationships, and importance varied between colonies.

Scientific Reports↗
USGS2007

Metallogeny of the nikolai large igneous province (LIP) in southern alaska and its influence on the mineral potential of the talkeetna mountains

Recent geologic mapping has identified areas of extrusive basalts of the Middle to Late Triassic Nikolai Greenstone within the Wrangellia terrane that extend at least 80 km southwest of their previously known extent. Abundant dolerite sills of similar composition intrude Paleozoic and Mesozoic stratigraphy below the Nikolai throughout the central Talkeetna Mountains. The Talkeetna Mountains, therefore, have newly identified potential for copper, nickel, and platinum-group elements (PGEs) as disseminated, net-textured, or massive magmatic sulfide deposits hosted in mafic and ultramafic sill-form complexes related to emplacement of the Nikolai. Because of their potential high grades, similar magmatic sulfide targets have been the focus of increasing mineral exploration activity over the last decade in the Amphitheater Mountains and central Alaska Range, 100-200 km to the northeast. The Nikolai Greenstone, associated intrusions, and their metamorphosed equivalents also have potential to host stratabound disseminated "basaltic copper" deposits. Sedimentary and metasedimentary rocks overlying the Nikolai have the potential to host stratabound, disseminated, or massive "reduced-facies" type Cu-Ag deposits. Ultramafic rocks have been identified only in the extreme northeastern Talkeetna Mountains to date. However, coincident gravity and magnetic highs along the leading (northwestern) edge of and within Wrangellia in the Talkeetna and Clearwater Mountains suggest several areas that are highly prospective for ultramafic rocks related to extrusion of Nikolai lavas. In particular, the distribution, geometry, and composition of sills within the pre-Nikolai stratigraphy and the structural and tectonic controls on intrusive versus extrusive rock distribution deserve serious examination. Copyright ?? 2007 The Geological Society of America.

Special Paper of the Geological Society of America↗
USGS1997

Delineating paleochannels using shallow seismic reflection

Discontinuous confining units beneath industrialized areas provide effective pathways for contaminants to move from one aquifer to another within Atlantic Coastal Plain sediments. Shallow seismic reflection can provide coherent high resolution images of thin, alternating sand and clay sequences in many shallow water table environments — useful, cost‐effective information which can significantly enhance environmental investigations.

Leading Edge (Tulsa, OK)↗
USGS1997

Induced polarization research at Kennecott, 1965-1977

Geophysics research and development (R&D) was a small research group at Kennecott Inc. (KEI), a subsidiary of Kennecott Copper Corporation. The research group served Geophysics-Operations, which in turn worked for another subsidiary, Bear Creek Mining Company (BCMC). BCMC did Kennecott's exploration work such as reconnaissance mapping, staking and proving up claims, and assessment drilling. The working environment at Geophysics R&D included emphasis on instrument development and being strongly field oriented; having entrepreneurial leaders engaged in technical work; interaction between R&D and its `customer', the Operations group and; emphasis on lowering costs and increasing production.

Leading Edge (Tulsa, OK)↗
USGS2002

A source-depth separation filter: Using the Euler method on the derivatives of total intensity magnetic anomaly data

Derivatives of potential-field anomalies (or the anomaly gradients) enhance the field associated with shallow features and de-emphasize the field from deeper sources. The derivative approach of separating anomalies of shallow, intermediate, and deep sourves is, however, qualitative. Semiautomatic source location methods, such as the Euler method (also variously referred to in the literature as Euler's theorem on homogeneous functions, Euler's differential equation, EULDPH, and Euler deconvolution), the analytic signal method, and Werner deconvolution, developed since the 1980s use anomaly gradients to characterize sources of anomalies (i.e., the type of sources and their locations). In this article, we investigate the benefits of applying the Euler method on derivatives of anomalies to enhance the location of shallow and deep sources. Used appropriately, the method is suitable for characterizing sources from all potential-field data and/or their derivatives, as long as the data can be regarded mathematically as “continuous.” We also explain the reasons why the use of the Euler method on derivatives of anomalies is particularly helpful in the analysis and interpretation of shallow features.

Leading Edge (Tulsa, OK)↗
USGS2002

Upgraded gravity anomaly base of the United States

A concerted effort to compile an upgraded gravity anomaly database, grid, and map for the United States by the end of 2002 is under way. This effort can be considered as the first step in building a data system for gravity measurements, and it builds on existing collaborative efforts. This paper outlines the strategy for assembling the individual map and digital products related to the United States gravity database.

Conterminous United States↗
USGS2001

New digital magnetic anomaly database for North America

The Geological Survey of Canada (GSC), U.S. Geological Survey (USGS), and Consejo de Recursos Minerales of Mexico (CRM) are compiling an upgraded digital magnetic anomaly database and map for North America. This trinational project is expected to be completed by late 2002.

The Leading Edge↗