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At least 235 records · Page 13Linked to original sources
USGS2011

The interactions between vegetation and erosion: new directions for research at the interface of ecology and geomorphology

Vegetation and processes of erosion and deposition are interactive. An objective of this paper is to review selected studies that emphasize the interdependencies. The reviews suggest new directions for research uniting ecology and geomorphology – the sub‐discipline of biogeomorphology. The research, which recently has become vigorous, includes the sources, movement, and fates of fluvial loads of sediment, organic carbon, nutrients, contaminants, and woody debris to low‐energy storage sites; the function of biota in causing soil evolution, stability, and sequestration of carbon; the development of new methods to characterize watersheds based on edaphic conditions; and the refinement of current empirical and conceptual models and dendrochronological techniques to measure landscape change. These well acknowledged topics and others less well anticipated ensure that biogeomorphology will remain vibrant.

Earth Surface Processes and Landforms↗
USGS1974

Electrophoresis as a management tool

The theme of this 1974 Northeast Fish and Wildlife Conference is 'A New Era'. Indeed, it is a new era for improved techniques to assist in management of our fish and wildlife resources for the maximum benefit of all. In some cases, the new techniques are primarily used in research.on fish and wildlife, and the results from the research are used to aid management and enforcement agencies in the decision-making process. One of the newer techniques that is being applied to problems in fisheries and wildlife is electrophoresis. In this paper, we review briefly the techniques of electrophoresis and illustrate research problems in wildlife and fisheries where the use of electrophoresis is now assisting or may potentially aid in management decisions.

Transactions of the Northeast Fish and Wildlife Co↗
USGS1986

USGS research on energy resources, 1986; program and abstracts

The extended abstracts in this volume are summaries of the papers presented orally and as posters in the second V. E. McKelvey Forum on Mineral and Energy Resources, entitled "USGS Research on Energy Resources-1986." The Forum has been established to improve communication between the USGS and the earth science community by presenting the results of current USGS research on nonrenewable resources in a timely fashion and by providing an opportunity for individuals from other organizations to meet informally with USGS scientists and managers. It is our hope that the McKelvey Forum will help to make USGS programs more responsive to the needs of the earth science community, particularly the mining and petroleum industries, and Win foster closer cooperation between organizations and individuals. The Forum was named after former Director Vincent E. McKelvey in recognition of his lifelong contributions to research, development, and administration in mineral and energy resources, as a scientist, as Chief Geologist, and as Director of the U.S. Geological Survey. The Forum will be an annual event, and its subject matter will alternate between mineral and energy resources. We expect that the format will change somewhat from year to year as various approaches are tried, but its primary purpose will remain the same: to encourage direct communication between USGS scientists and the representatives of other earth-science related organizations. Energy programs of the USGS include oil and gas, coal, geothermal, uranium-thorium, and oil shale; work in these programs spans the national domain, including surveys of the offshore Exclusive Economic Zone. The topics selected for presentation at this McKelvey Forum represent an overview of the scientific breadth of USGS research on energy resources. They include aspects of petroleum occurrence in Eastern United States rift basins, the origin of magnetic anomalies over oil fields, accreted terranes and energy-resource implications, coal quality, geothermal energy sources, integrated geology and chemistry in uranium-deposit studies, and interpretations of sea-floor geology seen in reconnaissance-scale sidescan-sonar mosaics of the Gulf of Mexico and west coast Exclusive Economic Zone. Data are presented that are being used in building models of geothermal energy settings, basin histories, and the occurrence of energy resources. In addition to the technical sessions presenting the results of USGS research, each congressionally mandated USGS Mineral Resource Program has a display outlining plans and progress. We are all excited about this continuing opportunity to disseminate and discuss our research with our colleagues in industry and academia, and we welcome your suggestions on improving this series of Forums.

Circular↗
USGS2006

Reserve Growth in Oil Fields of West Siberian Basin, Russia

Although reserve (or field) growth has proven to be an important factor contributing to new reserves in mature petroleum basins, it is still a poorly understood phenomenon. Limited studies show that the magnitude of reserve growth is controlled by several major factors, including (1) the reserve booking and reporting requirements in each country, (2) improvements in reservoir characterization and simulation, (3) application of enhanced oil recovery techniques, and (4) the discovery of new and extensions of known pools in discovered fields. Various combinations of these factors can affect the estimates of proven reserves in particular fields and may dictate repeated estimations of reserves during a field's life. This study explores the reserve growth in the 42 largest oil fields in the West Siberian Basin, which contain about 55 percent of the basin's total oil reserves. The West Siberian Basin occupies a vast swampy plain between the Ural Mountains and the Yenisey River, and extends offshore into the Kara Sea; it is the richest petroleum province in Russia. About 600 oil and gas fields with original reserves of 144 billion barrels of oil (BBO) and more than 1,200 trillion cubic feet of gas (TCFG) have been discovered. The principal oil reserves and most of the oil fields are in the southern half of the basin, whereas the northern half contains mainly gas reserves. Sedimentary strata in the basin consist of Upper Triassic through Tertiary clastic rocks. Most oil is produced from Neocomian (Lower Cretaceous) marine to deltaic sandstone reservoirs, although substantial oil reserves are also in the marine Upper Jurassic and continental to paralic Lower to Middle Jurassic sequences. The majority of oil fields are in structural traps, which are gentle, platform-type anticlines with closures ranging from several tens of meters to as much as 150 meters (490 feet). Fields producing from stratigraphic traps are generally smaller except for the giant Talin field which contains oil in Jurassic river-valley sandstones. Principal source rocks are organic-rich marine shales of the Volgian (uppermost Jurassic) Bazhenov Formation, which is 30-50 m (98- 164 feet) thick. Bazhenov-derived oils are mostly of medium gravity, and contain 0.8-1.3 percent sulfur and 2-5 percent paraffin. Oils in the Lower to Middle Jurassic clastics were sourced from lacustrine and estuarine shales of the Toarcian Togur Bed. These oils are medium to low gravity, with low sulfur (less than 0.25 percent) and high paraffin (commonly to 10 percent) contents. Among the 42 fields analyzed for reserve growth, 30 fields are located in the Middle Ob region, which includes the Samotlor field with reserves of more than 25 BBO and the Fedorov field with reserves of about 5 BBO. Data used in the study include year of discovery, year of first production, annual and cumulative production, and remaining reserves reported by Russian reserve categories (A+B+C1 and C2) in January of each year. Correlation of these Russian resource categories to U.S. categories of the Society of Petroleum Engineers classification is complex and somewhat uncertain. Reserve growth in oil fields of West Siberia was calculated using a newly developed Group Growth method, which requires that the total reserve (proven reserve plus cumulative production) of individual fields with an equal length of reserve record be added together starting with discovery year or the first production year. Then the annual growth factor (AGF), which is the ratio of total reserves of two consecutive years, is calculated for all years. Once AGFs have been calculated, the cumulative growth factor (CGF) is calculated by multiplying the AGFs of all the previous years. The CGF data are used to develop reserve growth models. The West Siberian oil fields show a 13-fold reserve growth 20 years after the discovery year and only about a 2-fold growth after the first production year. This difference is attributed to extensive exploration and field delineation activities between the discovery and the first production years. Because of uncertainty in the length of evaluation time and in reported reserves during this initial period, reserve growth based on the first production year is more reliable for model development. However, reserve growth models based both on discovery year and first production year show rapid growth in the first few years and slower growth in the following years. In contrast, the reserve growth patterns for the conterminous United States and offshore Gulf of Mexico show a steady reserve increase throughout the productive lives of the fields. The different reserve booking requirements and the lack of capital investment for improved reservoir management and production technologies in West Siberian fields relative to U.S. fields are the probable causes for the difference in growth patterns. Reserve growth models based on the first production year predict that the reserve growth potential in the 42 largest oil fields of West Siberia over a five-year period (1998-2003) ranges from 270-330 million barrels or 0.34-0.42 percent per year. For a similar five-year period (1996-2001), models for the conterminous United States predict a growth of 0.54-0.75 percent per year. This abstract presents the contents of a poster prepared for the AAPG Hedberg Research Conference on Understanding World Oil Resources, November 12-17, 2006 - Colorado Springs, Colorado. A paper 'Reserve Growth in Oil Fields of West Siberian Basin, Russia' was published in Natural Resources Research, v. 12, no. 2, June, 2003.

Open-File Report↗
USGS1996

Small watershed studies: Analytical approaches for understanding ecosystem response to environmental change

Biogeochemical studies in small watersheds provide an analytical approach to understand how ecosystems respond to natural climatic variations and human-induced environmental change. Small watersheds, usually less than 5 km2, are small enough to permit characterization and understanding of ecosystem processes within relatively simple, homogeneous biological and physical settings; yet they are large enough to incorporate more complex processes and element cycles than can be studied at plot scales. Watersheds comprise discrete hydrochemical environments allowing quantification of hydrologic, element, and energy budgets. Element budgets, or mass balances, can be quantified as the difference between the mass of a solute that enters a watershed in wet and dry deposition and leaves a watershed in streamflow. Element budgets are primary tools used to investigate biogeochemical processes. Monitoring various aspects of element budgets to assess ecosystem health and stability is analogous to measuring the pulse or blood chemistry of a patient. Monitoring streamwater chemistry, basic climate, soil, and biotic variables provide a means to integrate complex biogeochemical processes and evaluate trends in water quality. Small watershed studies provide a scientific basis to develop predictive models of watershed function. Major emphases of small watershed studies include investigation of hydrologic and chemical responses to natural climate variation, anthropogenic stressors, and alternate forest-management practices. The nature and significance of biogeochemical research in small watersheds is reviewed by Moldan and Cerny (1994). The U.S. Geological Survey, U.S. Department of Agriculture Forest Service, and other federal agencies support several long-term small watershed studies to provide insight into a variety of ecosystem processes. Long-term records are essential to distinguish trends resulting from natural climatic variations or other stressors. The following sites, with noted periods of records, are examples of intensively studied forested watersheds in eastern USA supported by federal agencies: ■ Coweeta Hydrologic Laboratory, North Carolina, (1939-present), Swank and Crossley (1988). ■ Hubbard Brook Experimental Forest, New Hampshire, (1956-present), Bormann and Likens (1979). ■ Sleepers River Research Watershed, Vermont, (1958-present), Shanley et al. (1995). ■ Walker Branch Watershed, Tennessee, (1967-present), Johnson and Van Hook (1989). ■ Catoctin Mountains Research Site, Maryland, (1982-present), Rice and Bricker (1995). ■ Catskill Stream Network, New York, (1983- present), Murdoch and Stoddard (1992). ■ Panola Mountain Research Watershed, Georgia, (1985-present), Huntington et al. (1993). Small watershed studies also provide essential baseline information for understanding variations in water quality and element cycling in "pristine" ecosystems that can be used as benchmarks to evaluate anthropogenic impacts and alternate watershed management practices. This paper provides examples of how analytical tools developed through watershed research provide insight into ecosystem processes and can contribute to the management of watershed resources.

Conference Paper↗
USGS1999

Natural attenuation of chloroacetinilide herbicides in aquatic systems

Chloroacetanilide herbicides (e.g. alachlor and metolachlor) and their breakdown products are frequently found in agriculturally impacted and other natural waters. Although these compounds are usually present at low concentrations in aquatic systems, defining their fate and attenuation rate is important because they can be toxic at comparatively low exposure levels. This paper summarizes results from a four-year research program assessing factors that affect herbicide attenuation rates and breakdown product formation patterns in aquatic systems. Over 70 different field microcosms (11.3 m 3 cylindrical fiberglass tanks) were selectively manipulated (in replicate) to create nine unique aquatic ecosystems for this study. Alachlor and/or metolachlor were added to these units and transformations were observed over time. Alachlor half-lives ranged from 6.0 days to more than 100 days depending upon the temperature, oxygen conditions, and the nutrient conditions in the microcosm waters. The highest rates of alachlor decay were observed in warm, nutrient-rich, anaerobic water columns, whereas the lowest alachlor decay rates were observed under cooler, aerobic, oligotrophic water conditions. Similar relationships were observed for metolachlor, although metolachlor decay rates were about 40% slower. Our data suggest that herbicides will decay rapidly in waters that are high in nutrients possibly resulting from human activities. Alternately, low nutrient or pristine waters will have the lowest rates of herbicide decay. On a policy level, all efforts should be made to prevent exposure of comparatively pristine waters to herbicide inputs.

Conference Paper↗
USGS1998

Recreation ecology research findings: Implications for wilderness and park managers

Recreationists unintentionally trample vegetation, erode soil, and disturb wildlife. Such human-related impacts present a dilemma for managers charged with the dual objectives of providing recreational opportunities and preserving natural environments. This paper presents some of the principal findings and management implications from research on visitor impacts to protected areas, termed recreation ecology research. This field of study seeks to identify the type and extent of resource impacts and to evaluate relationships between use-related, environmental, and managerial factors. The capabilities and managerial utility of recreation impact monitoring are also described.

Book chapter↗
USGS1994

Measurement of radon gas on major faults in California, USA

Abundant data have been gathered through measurements of radon gas emission in the soil on several major active faults, such as San Andreas and Calaveras, in California, U.S.A.. They show radon emissions and their spatial variations at the unlocked, locked, and creeping sections of faults with different tectonic movements. The characteristics of these variations and the role of fault gases in the research on earthquake prediction are discussed in this paper. ?? 1994 Acta Seismologica Sinica.

Acta Seismologica Sinica↗
USGS2019

Integrating amphibian movement studies across scales better informs conservation decisions

Numerous papers have highlighted the need to integrate amphibian research and conservation across multiple scales. Despite this, most amphibian movement studies focus on a single level of organization (e.g., local population) and a single life stage (e.g., adults) and many suggest potential conservation actions or imply that the information is useful to conservation, yet these presumptions are rarely clarified or tested. Movement studies to date provide little information to guide conservation decisions directly because they fail to integrate movement across scales with individual or population parameters (i.e., fitness metrics); this is exacerbated by a general failure to set movement studies in a probabilistic context. An integrative approach allows prediction of population or metapopulation responses to environmental changes and different management actions, thus directly informing conservation decisions and ‘moving the needle’ towards an informed application of conservation actions. To support this perspective we: 1) revisit reviews of amphibian movement to illustrate the focus on single scales and to underscore the importance of movement – at all scales – to conservation; 2) make the case that movement, breeding, and other demographic probabilities are intertwined and studies executed at different temporal and spatial scales can aid in understanding species' responses to varying environmental and/or management conditions; 3) identify limitations of existing movement-related research to predict conservation action outcomes and inform decision-making; and 4) highlight under-utilized quantitative approaches that facilitate research that either connects movement to fitness metrics (individual-level studies) or estimates population and metapopulation vital rates in addition to, or associated with, movement probabilities.

Biological Conservation↗
USGS2018

Examining the relationship between portable luminescence reader measurements and depositional ages of paleowetland sediments, Las Vegas Valley, Nevada

Portable luminescence readers are exciting new tools that have the potential to rapidly determine the age structure of late Quaternary stratigraphic columns. This is important because high-resolution age profiling can reveal details about the temporal dynamics of climate cause and ecosystem effect, often while researchers are still in the field. In this paper, we compare new portable luminescence reader measurements of total photon counts with a suite of robust, highly resolved ages from middle to late Pleistocene-age paleowetland deposits in the Las Vegas Valley of southern Nevada. Our results show that total photon counts correlate with age, with a quadratic equation providing the best fit to the data. Significant scatter is present in the data, which is likely the result of dose rate variations, multiple sediment sources, and transport mechanisms that include both eolian and fluvial processes. The observed scatter can be reduced significantly using a simple pretreatment procedure involving a 250 μm sieve and neodymium hand magnet to normalize particle sizes and remove magnetic grains. Following this treatment, age estimates based on the reader measurements have an average error of 30 ± 18% when compared against known ages. These findings confirm that portable reader measurements scale with age in paleowetland deposits, allowing its use in establishing rapid, albeit approximate, chronologies for these deposits throughout the American Southwest.

Nevada↗
USGS2013

Selection of hyperspectral narrowbands (HNBs) and composition of hyperspectral twoband vegetation indices (HVIs) for biophysical characterization and discrimination of crop types using field reflectance and Hyperion/EO-1 data

The overarching goal of this study was to establish optimal hyperspectral vegetation indices (HVIs) and hyperspectral narrowbands (HNBs) that best characterize, classify, model, and map the world's main agricultural crops. The primary objectives were: (1) crop biophysical modeling through HNBs and HVIs, (2) accuracy assessment of crop type discrimination using Wilks' Lambda through a discriminant model, and (3) meta-analysis to select optimal HNBs and HVIs for applications related to agriculture. The study was conducted using two Earth Observing One (EO-1) Hyperion scenes and other surface hyperspectral data for the eight leading worldwide crops (wheat, corn, rice, barley, soybeans, pulses, cotton, and alfalfa) that occupy ~70% of all cropland areas globally. This study integrated data collected from multiple study areas in various agroecosystems of Africa, the Middle East, Central Asia, and India. Data were collected for the eight crop types in six distinct growth stages. These included (a) field spectroradiometer measurements (350-2500 nm) sampled at 1-nm discrete bandwidths, and (b) field biophysical variables (e.g., biomass, leaf area index) acquired to correspond with spectroradiometer measurements. The eight crops were described and classified using ~20 HNBs. The accuracy of classifying these 8 crops using HNBs was around 95%, which was ~ 25% better than the multi-spectral results possible from Landsat-7's Enhanced Thematic Mapper+ or EO-1's Advanced Land Imager. Further, based on this research and meta-analysis involving over 100 papers, the study established 33 optimal HNBs and an equal number of specific two-band normalized difference HVIs to best model and study specific biophysical and biochemical quantities of major agricultural crops of the world. Redundant bands identified in this study will help overcome the Hughes Phenomenon (or “the curse of high dimensionality”) in hyperspectral data for a particular application (e.g., biophysi- al characterization of crops). The findings of this study will make a significant contribution to future hyperspectral missions such as NASA's HyspIRI.

Africa;Central Asia;Middle East↗
USGS2002

Mechanisms of impact and potential recovery of nearshore vertebrate predators following the 1989 Exxon Valdez oil spill

The 1989 spill of some 42 million L of crude oil into Prince William Sound, Alaska, represents not only the largest tanker spill in United States history, but the world’s largest spill in northern waters. Acute effects have been studied extensively. However, efforts to quantify the spill’s long-term chronic effects and develop defensible restoration measures have been plagued by varying levels of scientific uncertainty. That such uncertainty exists is not unexpected. The spill occurred in Prince William Sound’s highly variable physical setting typified by its complex oceanography and fjord-like geomorphology. Additionally, uncertainty was driven by the scarcity of precise pre-spill population estimates and spotty life-history information for most species. The research reported herein in, structured in eight primary papers and 27 supporting papers (appendices), documents the state of recovery and assessments of continuing constraints to population recovery for four vertebrate predators (sea otter Enhydra lutris , harlequin duck Histrionicus histrionicus , river otter Lontra canadensis , and pigeon guillemot Cepphus columba ) whose recovery status remained uncertain some 5 years after the Exxon Valdez oil spill. These species are used in a collective weight of evidence approach to better understand the process of coastal community recovery. Each species is examined for the strength of information it brings in health, population, and trophic metrics to support or reject the hypothesis of continuing oil effects in the nearshore system versus the alternatives that food constraints or demographic bottlenecks limit these focal species. While data for individual species contain various levels of uncertainty, scientific confidence is developed in the following picture when examined across species, metric, and hypothesis: Within the nearshore coastal environment, sporadic releases of residual oil are occurring, and benthic species, primarily invertebrates, are being exposed in a temporally and spatially patchy manner sufficient to transport oil up through the food chain. Thus, for the two invertebrate-feeders, sea otter and harlequin duck, evidence exists over several lines of investigation to suggest that local-scale populations continue to be constrained not by food availability or natural demographic processes, but by increased levels of mortality coincident with continued exposure to residual oil. Conversely, weight of evidence suggests that only limited direct oil-related effects are being transferred through the fish trophic pathway. Sufficient evidence suggests recovery is occurring in river otter populations, while the lack of recovery in pigeon guillemot may be attributed to food limitations (both natural and indirectly related to the spill) and/or slow demographic response to initial acute mortalities. Individual lines of investigation often contained uncertainty, but the collective weight of evidence presented in this multipaper volume indicates lack of full recovery of the nearshore ecosystem from the Exxon Valdez oil spill nearly a decade following the event. Integrated, multispecies approaches can allow sufficient weight of evidence to develop despite inherent system variability or data limitations and, thus, facilitate both better societal understanding of such pollution events and development of appropriate restoration responses.

Alaska↗
USGS1994

Crude-oil spill research project near Bemidji, Minnesota - Bibliography, 1984-1994

The U.S. Geological Survey began a research project at the site of a crude-oil spill near Bemidji, Minnesota in 1983. The project is part of the U.S. Geological Survey's Toxic Substances Hydrology Program. The objectives of research at the site are to obtain an understanding of the mobilization, transport, and fate of petroleum derivatives in the shallow subsurface and to use this understanding to develop predictive models of contaminant behavior. This report presents a bibliography of scientific papers that have been published from 1984 to early 1994. Research results have been published in scientific journals, conference proceedings, U.S. Geological Survey Reports, and academic theses.

Open-File Report↗
USGS1957

U.S. Federal fishery research on the Great Lakes through 1956

The major purpose of this publication is to present an annotated bibliography of papers resulting from Federal investigations on the Great Lakes fish and fisheries since the formal initiation of a continuing research program by the Fish and Wildlife Service. It is believed that this purpose can be served best by prefacing that bibliography with a brief account of the origins of Great Lakes Fishery Investigations, of the circumstances that have guided their course. The present article is a revision and expansion of the author's earlier publication: 25 years of Federal Fishery Research on the Great Lakes (Special Scientific Report-Fisheries No. 85, 1952). Two circumstances made a revision desirable at this time. First, publications since 1952 have added greatly to the literature based on Federal studies on the Great Lakes. Second, the Great Lakes Fishery Commission, established by treaty with Canada, was organized in Ottowa in April 1956 and held its first annual meeting in Ann Arbor in November 1956. The entry of the Commission on the scene marks the start of an era of further expansion and heightens in past activities.

Special Scientific Report - Fisheries↗
USGS1996

Joint US Geological Survey, US Nuclear Regulatory Commission workshop on research related to low-level radioactive waste disposal, May 4-6, 1993, National Center, Reston, Virginia; Proceedings

This report contains papers presented at the "Joint U.S. Geological Survey (USGS) and U.S. Nuclear Regulatory Commission (NRC) Technical Workshop on Research Related to Low-Level Radioactive Waste (LLW) Disposal" that was held at the USGS National Center Auditorium, Reston, Virginia, May 4-6, 1993. The objective of the workshop was to provide a forum for exchange of information, ideas, and technology in the geosciences dealing with LLW disposal. This workshop was the first joint activity under the Memorandum of Understanding between the USGS and NRC's Office of Nuclear Regulatory Research signed in April 1992. Participants included invited speakers from the USGS, NRC technical contractors (U.S. Department of Energy (DOE) National Laboratories and universities) and NRC staff for presentation of research study results related to LLW disposal. Also in attendance were scientists from the DOE, DOE National Laboratories, the U.S. Environmental Protection Agency, State developmental and regulatory agencies involved in LLW disposal facility siting and licensing, Atomic Energy Canada Limited (AECL), private industry, Agricultural Research Service, universities, USGS and NRC.

Water-Resources Investigations Report↗
USGS1995

Beyond the petroleum system: GEOHORIZONS

The first joint AAPG/AMGP (Association of Mexican Petroleum Geologists) Hedberg Conference on “Geologic Aspects of Petroleum Systems” was held October 2–6, 1994, in Mexico City, Mexico. This research conference attracted nearly 150 geoscientists from 15 countries; 41 papers and 27 posters were presented. The opposite response occurred when the petroleum-system concept was presented more than 20 yr ago; it was largely overlooked. In the past decade, however, interest in this concept as an exploration tool has been growing rapidly. The research conference addressed the concept itself, its elements and processes, the tools and methods used to identify a petroleum system, and many case studies. We summarize responses by the participants to the following three questions. First, what is gained from using the petroleum-system concept? Second, in what new directions will the petroleum-system concept take us in the future? Third, has anything new come out of this research conference?

American Association of Petroleum Geologists Bulle↗
USGS2014

NGA-West2 Research Project

The NGA-West2 project is a large multidisciplinary, multi-year research program on the Next Generation Attenuation (NGA) models for shallow crustal earthquakes in active tectonic regions. The research project has been coordinated by the Pacific Earthquake Engineering Research Center (PEER), with extensive technical interactions among many individuals and organizations. NGA-West2 addresses several key issues in ground-motion seismic hazard, including updating the NGA database for a magnitude range of 3.0–7.9; updating NGA ground-motion prediction equations (GMPEs) for the “average” horizontal component; scaling response spectra for damping values other than 5%; quantifying the effects of directivity and directionality for horizontal ground motion; resolving discrepancies between the NGA and the National Earthquake Hazards Reduction Program (NEHRP) site amplification factors; analysis of epistemic uncertainty for NGA GMPEs; and developing GMPEs for vertical ground motion. This paper presents an overview of the NGA-West2 research program and its subprojects.

Earthquake Spectra↗