United States Geological Survey

About: United States Geological Survey is a government organization based out in Reston, Virginia, United States. It is known for research contribution in the topics: Population & Groundwater. The organization has 17899 authors who have published 51097 publications receiving 2479125 citations. The organization is also known as: USGS & US Geological Survey.

Source mechanisms of explosions at Stromboli Volcano, Italy, determined from moment-tensor inversions of very-long-period data

Abstract: [1] Seismic data recorded in the 2–30 s band at Stromboli Volcano, Italy, are analyzed to quantify the source mechanisms of Strombolian explosions during September 1997. To determine the source-centroid location and source mechanism, we minimize the residual error between data and synthetics calculated by the finite difference method for a point source embedded in a homogeneous elastic medium that takes topography into account. Two source centroids are identified, each representative of the distinct event types associated with explosive eruptions from two different vents. The observed waveforms are well reproduced by our inversion, and the two source centroids that best fit the data are offset 220 and 260 m beneath and � 160 m northwest of the active vents. The source mechanisms include both moment-tensor and single-force components. The principal axes of the moment tensor have amplitude ratios 1:1:2, which can be interpreted as representative of a crack, if one assumes the rock matrix at the source to have a Poisson ratio n = 1/3, a value appropriate for hot rock. Both imaged cracks dip � 60� to the northwest and strike northeast–southwest along a direction parallel to the elongation of the volcanic edifice and a prominent zone of structural weakness, as expressed by lineaments, dikes, and brittle structures. For our data set, the volume changes estimated from the moments are � 200 m 3 for the largest explosion from each vent. Together with the volumetric source is a dominantly vertical force with a magnitude of 10 8 N, consistent with the inferred movement of the magma column perched above the source centroid in response to the piston-like rise of a slug of gas in the conduit. INDEX TERMS: 7215 Seismology: Earthquake parameters; 7280 Seismology: Volcano seismology (8419); 8414 Volcanology: Eruption mechanisms; KEYWORDS: very-long-period seismicity, moment tensor inversions, eruption mehanics

Toward Production From Gas Hydrates: Current Status, Assessment of Resources, and Simulation-Based Evaluation of Technology and Potential

Abstract: Toward Production From Gas Hydrates: Current Status, Assessment of Resources, and Simulation-Based Evaluation of Technology and Potential George J. Moridis, SPE, Lawrence Berkeley National Laboratory; Timothy S. Collett, SPE, US Geological Survey; Ray Boswell, US Department of Energy; M. Kurihara, SPE, Japan Oil Engineering Company; Matthew T. Reagan, SPE, Lawrence Berkeley National Laboratory; Carolyn Koh and E. Dendy Sloan, SPE, Colorado School of Mines This paper was prepared for presentation at the 2008 SPE Unconventional Reservoirs Conference held in Keystone, Colorado, U.S.A., 10–12 February 2008. Abstract Gas hydrates are a vast energy resource with global distribution in the permafrost and in the oceans. Even if conservative estimates are considered and only a small fraction is recoverable, the sheer size of the resource is so large that it demands evaluation as a potential energy source. In this review paper, we discuss the distribution of natural gas hydrate accumulations, the status of the primary international RD Klauda and Sandler, 2005). Given the sheer magnitude of the resource, ever increasing global energy demand, and the finite volume of conventional fossil fuel reserves, gas hydrates are emerging as a potential energy source for a growing number of nations. The attractive- ness of gas hydrates is further enhanced by the environmental desirability of natural gas (as opposed to solid or liquid) fuels. Thus, the appeal of gas hydrate accumulations as future hydrocarbon gas sources is rapidly increasing and their production potential clearly demands technical and economic evaluation. The past decade has seen a marked acceleration in gas hydrate RD Paull et al., 2005), reservoir lithology, and rates and

Flow and habitat effects on juvenile fish abundance in natural and altered flow regimes

Abstract: Conserving biological resources native to large river systems increasingly depends on how flow-regulated segments of these rivers are managed. Improving management will require a better understanding of linkages between river biota and temporal variability of flow and instream habitat. However, few studies have quantified responses of native fish populations to multiyear (>2 yr) patterns of hydrologic or habitat variability in flow-regulated systems. To provide these data, we quantified young-of-year (YOY) fish abundance during four years in relation to hydrologic and habitat variability in two segments of the Tallapoosa River in the southeastern United States. One segment had an unregulated flow regime, whereas the other was flow-regulated by a peak-load generating hydropower dam. We sampled fishes annually and explored how continuously recorded flow data and physical habitat simulation models (PHABSIM) for spring (April–June) and summer (July–August) preceding each sample explained fish abundances. Patt...

Nitrogen input to the Gulf of Mexico.

Abstract: their percentage of the basin include woodland (18%), range and barren land (21%), wetlands and water (2.4%), Historical streamflow and concentration data were used in regresand urban land (0.6%). About 70 million people live sion models to estimate the annual flux of nitrogen (N) to the Gulf of Mexico and to determine where the nitrogen originates within the within the Mississippi basin, and it contains one of the Mississippi Basin. Results show that for 1980‐1996 the mean annual most productive farming regions in the world. The central total N flux to the Gulf of Mexico was 1 568 000 t yr 21 . The flux was part of the basin produces the majority of the corn, soyabout 61% nitrate N, 37% organic N, and 2% ammonium N. The bean, wheat, cattle, and hogs produced in the United flux of nitrate N to the Gulf has approximately tripled in the last 30 States. Because of the intensive agriculture, the majority years with most of the increase occurring between 1970 and 1983. of all fertilizers and pesticides used in the United States The mean annual N flux has changed little since the early 1980s, but are applied to cropland within the basin. In addition, large year-to-year variations in N flux occur because of variations in

Submarine Mass Movements and Their Consequences

Abstract: Submarine mass movements represent major offshore geohazards due to their destructive and tsunami-generation potential. This potential poses a threat to human life as well as to coastal, near shore and offshore engineering structures. Recent examples of catastrophic submarine landslide events that affected human populations (including tsunamis) are numerous; e.g., Nice airport in 1979 (Dan et al. 2007), Finneidfjord in 1996 (e.g., L’Heureux et al., this volume, Steiner et al., this volume), Papua-New Guinea in 1998 (Tappin et al. 2001), Stromboli in 2002 (Chiocci et al. 2008), and the 2006 and 2009 failures in the submarine cable network around Taiwan (Hsu et al. 2008). The Great East Japan Earthquake of March 2011 also generated submarine landslides that may have amplified effects of the devastating tsunami as shown in Fryer et al. (2004). Given that 30% of the World’s population lives within 60 km of the coast, the hazard posed by submarine landslides is expected to grow as global sea level rises. In addition, the deposits resulting from such processes provide-various types of constraints to offshore development (Shipp et al. 2004), and have significant implications for non-renewable energy resource exploration and production (Weimer and Shipp 2004; Beaubouef and Abreu 2010).