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At least 235 records · Page 13Linked to original sources
USGS2016

Best practices in passive remote sensing VNIR hyperspectral system hardware calibrations

Hyperspectral imaging (HSI) is an exciting and rapidly expanding area of instruments and technology in passive remote sensing. Due to quickly changing applications, the instruments are evolving to suit new uses and there is a need for consistent definition, testing, characterization and calibration. This paper seeks to outline a broad prescription and recommendations for basic specification, testing and characterization that must be done on Visible Near Infra-Red grating-based sensors in order to provide calibrated absolute output and performance or at least relative performance that will suit the user’s task. The primary goal of this paper is to provide awareness of the issues with performance of this technology and make recommendations towards standards and protocols that could be used for further efforts in emerging procedures for national laboratory and standards groups.

Conference Paper↗
USGS2005

Use of decision support systems as a drought management tool

Droughts present a unique challenge to water managers throughout the world and the current drought in the western United States is taxing facilities to the limit. Coping with this severe drought requires state of the art decision support systems including efficient and accurate hydrologic process models, detailed hydrologic data bases and effective river systems management modeling frameworks. This paper will outline a system of models developed by the Bureau of Reclamation, the US Geological Survey, the University of Colorado and a number of other governmental and university partners. The application of the technology to drought management in several key western river basins will be discussed.

Conference Paper↗
USGS2014

Aftershock risks such as those demonstrated by the recent events in New Zealand and Japan

Recent earthquakes in New Zealand and Japan show that it is important to consider the spatial and temporal distribution of aftershocks following large magnitude events since the probability of high intensity ground motions from aftershocks, which are capable of causing significant societal impact, can be considerable. This is due to the fact that a mainshock will have many aftershocks, some of which may occur closer to populated areas and may be large enough to cause damage. When a large magnitude event strikes a region, the chance that aftershocks will cause damage can be significant as was observed after the 2011 Tohoku and 2010 Canterbury earthquakes (e.g., damage caused by M w 6.6 April 11, 2011 Fukushima-Hamadori earthquake following Tohoku earthquake or by M w 6.3 February 22, 2011 Christchurch earthquake following Canterbury earthquake). Aftershock events may further damage already damaged buildings, thereby further complicating assessments of risk to the built environment. In this paper, the issue of aftershock risk is addressed by summarizing current research regarding: (1) aftershock hazard, (2) structural fragility/vulnerability before and after the mainshock, and (3) change in risk due to aftershocks.

Conference Paper↗
USGS2016

Undergraduate research projects help promote diversity in the geosciences

A workforce that draws from all segments of society and mirrors the ethnic, racial, and gender diversity of the United States population is important. The geosciences (geology, hydrology, geospatial sciences, environmental sciences) continue to lag far behind other science, technology, engineering and mathematical (STEM) disciplines in recruiting and retaining minorities (Valsco and Valsco, 2010). A report published by the National Science Foundation in 2015, “Women, Minorities, and Persons with Disabilities in Science and Engineering” states that from 2002 to 2012, less than 2% of the geoscience degrees were awarded to African-American students. Data also show that as of 2012, approximately 30% of African-American Ph.D. graduates obtained a bachelor’s degree from a Historic Black College or University (HBCU), indicating that HBCUs are a great source of diverse students for the geosciences. This paper reviews how an informal partnership between Tennessee State University (a HBCU), the U.S. Geological Survey, and Mammoth Cave National Park engaged students in scientific research and increased the number of students pursuing employment or graduate degrees in the geosciences.

Conference Paper↗
USGS1963

Simple measurements of morphological changes in river channels and hillslopes

One of the principal types of observational evidence on climatic changes in the recent geologic past is in river position and elevation. It is well known that river channels, particularly those flowing through alluvium or on relatively soft bedrock, tend to develop flood plains by lateral migration of the channel. Abandoned flood plains at elevations distinctly above the present river channel are the origin of river terraces, widespread through the world but particularly noticeable in arid regions. Climatic change is one of the causes of the abandonment of flood plains and the consequent formation of river terraces. Therefore, the identification and stratigraphy of river terraces is one of the methods by which climatic changes in the recent geologic past can be studied. There are, of course, morphologic changes in river channels of a more subtle nature. Even when a channel is progressively degrading-a trend which will eventually result in the formation of a river terracethere are no obvious criteria by which the current changes in a river channel can be positively identified. For this reason simple techniques, which will aid in the direct observation of current changes in a channel’s position, can be helpful in identifying the nature of changes in progress. It is the purpose of this paper to describe some relatively simple techniques which have been found to be useful in observing morphological changes on slopes and in channels. The methods have been tested primarily in arid climates but to some extent they can also be useful even where vegetation is prominent.

Conference Paper↗
USGS1992

Remote sensing of water clarity and suspended sediments in coastal waters

Processing of data for estimation of suspended sediment concentrations and water clarity in turbid coastal water requires three components: (1) correction of raw data to water reflectance; (2) establishment of appropriate general models relating reflectance characteristics to materials in the water; and (3) determination of the coefficients of the models appropriate for the area under study. This paper presents equations and procedures appropriate for this processing. It provides example coefficients and data for the NOAA advanced very high resolution radiometer, which is the most appropriate sensor for investigating larger estuaries and turbid coastal systems until the launch of an ocean color imager (SeaWiFS) in late 1993.

Conference Paper↗
USGS2012

Improving wetland simulations by including heat transport in groundwater flow modeling

A procedure was developed to automatically calibrate a groundwater flow and heat transport model, resulting in the estimation of hydraulic conductivity and flux across the water table in wetland systems. This paper describes differences between previous approaches and this study, and summarizes some challenges in the method implementation. The procedure was validated in a sequence of hypothetical models with known structure and parameters, and applied to a wetlands system located near Wilton, Wisconsin. Copyright ASCE 2004.

Conference Paper↗
USGS2011

On the powerful use of simulations in the quake-catcher network to efficiently position low-cost earthquake sensors

The Quake-Catcher Network (QCN) uses low-cost sensors connected to volunteer computers across the world to monitor seismic events. The location and density of these sensors' placement can impact the accuracy of the event detection. Because testing different special arrangements of new sensors could disrupt the currently active project, this would best be accomplished in a simulated environment. This paper presents an accurate and efficient framework for simulating the low cost QCN sensors and identifying their most effective locations and densities. Results presented show how our simulations are reliable tools to study diverse scenarios under different geographical and infrastructural constraints. ?? 2011 IEEE.

Conference Paper↗
USGS2004

Correlative weighted stacking for seismic data in the wavelet domain

Horizontal stacking plays a crucial role for modern seismic data processing, for it not only compresses random noise and multiple reflections, but also provides a foundational data for subsequent migration and inversion. However, a number of examples showed that random noise in adjacent traces exhibits correlation and coherence. The average stacking and weighted stacking based on the conventional correlative function all result in false events, which are caused by noise. Wavelet transform and high order statistics are very useful methods for modern signal processing. The multiresolution analysis in wavelet theory can decompose signal on difference scales, and high order correlative function can inhibit correlative noise, for which the conventional correlative function is of no use. Based on the theory of wavelet transform and high order statistics, high order correlative weighted stacking (HOCWS) technique is presented in this paper. Its essence is to stack common midpoint gathers after the normal moveout correction by weight that is calculated through high order correlative statistics in the wavelet domain. Synthetic examples demonstrate its advantages in improving the signal to noise (S/N) ration and compressing the correlative random noise.

Conference Paper↗
USGS2016

Field scale test of multi-dimensional flow and morphodynamic simulations used for restoration design analysis

Two- and three-dimensional morphodynamic simulations are becoming common in studies of channel form and process. The performance of these simulations are often validated against measurements from laboratory studies. Collecting channel change information in natural settings for model validation is difficult because it can be expensive and under most channel forming flows the resulting channel change is generally small. Several channel restoration projects designed in part to armor large meanders with several large spurs constructed of wooden piles on the Kootenai River, ID, have resulted in rapid bed elevation change following construction. Monitoring of these restoration projects includes post- restoration (as-built) Digital Elevation Models (DEMs) as well as additional channel surveys following high channel forming flows post-construction. The resulting sequence of measured bathymetry provides excellent validation data for morphodynamic simulations at the reach scale of a real river. In this paper we test the performance a quasi-three-dimensional morphodynamic simulation against the measured elevation change. The resulting simulations predict the pattern of channel change reasonably well but many of the details such as the maximum scour are under predicted.

Conference Paper↗
USGS2010

Topographic evolution of sandbars: Flume experiment and computational modeling

Measurements of sandbar formation and evolution were carried out in a laboratory flume and the topographic characteristics of these barforms were compared to predictions from a computational flow and sediment transport model with bed evolution. The flume experiment produced sandbars with approximate mode 2, whereas numerical simulations produced a bed morphology better approximated as alternate bars, mode 1. In addition, bar formation occurred more rapidly in the laboratory channel than for the model channel. This paper focuses on a steady-flow laboratory experiment without upstream sediment supply. Future experiments will examine the effects of unsteady flow and sediment supply and the use of numerical models to simulate the response of barform topography to these influences.

Conference Paper↗
USGS2012

Economic impacts of anthropogenic activities on coastlines of the United States

Anthropogenic activities primarily impact coasts by reducing sediment inputs, altering sediment transport processes, and accelerating sediment losses to the offshore. These activities include: sand and gravel extraction, navigation and shore protection works; non-structural shoreline management strategies such as beach nourishment, sand by-passing and beach scraping, dams and flood control works; channel and inlet dredging; subsidence caused by fluid extraction and reduction of carbonate beach material. Although many of these activities have improved the quality of life, they also have had unintended effects on the coast. The issues that arise from human alterations of the coast are common to many coastal regions around the world; this paper draws from several areas of the United States to present an overview and provisional assessment of the economic consequences of anthropogenic activities along the Pacific coast.

Pacific Coast↗
USGS2010

Ocean and coastal data management

We introduce data management concepts, including what we mean by "data" and its "management," sources of data, interoperability, and data geometry. We then discuss various components of a data management system. Finally, we summarize some existing ocean and coastal data management efforts. We make specific recommendations throughout the paper. We are generally optimistic that ocean and coastal data management is an interesting and solvable challenge that will provide great benefit to society.

Conference Paper↗
USGS1983

PROPOSED SPECIFICATIONS FOR INERTIAL SURVEYING.

The purpose of this paper is to continue the movement toward placing inertial surveying instruments in the toolbox of the geodetic surveyor. A set of specifications is proposed for performing horizontal geodetic surveys with inertial instruments that will meet the Federal Geodetic Control Committee (FGCC) second- and third-order standards. These specifications are tentative.

Conference Paper↗
USGS2005

Maximum known floodflows in Mississippi

Maximum floodflows (stream discharges) that are known to have occurred on Mississippi streams were compiled. Most data were collected and archived by the U.S. Geological Survey in cooperation with Federal, State, and local agencies; however, some data were collected and provided by the U.S. Army Corps of Engineers. Maximum known discharges are plotted with drainage area and compared to an envelope curve derived from maximum known discharges at sites throughout the conterminous United States. This paper presents the maximum flood known to have occurred at a given gaged site, where stage and discharge measurements were obtained to determine the peak discharge, or at an ungaged site, where a flood was thought to be significant enough that an indirect measurement was computed to estimate the peak discharge.

Conference Paper↗
USGS2011

Tsunami risk mapping simulation for Malaysia

The 26 December 2004 Andaman mega tsunami killed about a quarter of a million people worldwide. Since then several significant tsunamis have recurred in this region, including the most recent 25 October 2010 Mentawai tsunami. These tsunamis grimly remind us of the devastating destruction that a tsunami might inflict on the affected coastal communities. There is evidence that tsunamis of similar or higher magnitudes might occur again in the near future in this region. Of particular concern to Malaysia are tsunamigenic earthquakes occurring along the northern part of the Sunda Trench. Further, the Manila Trench in the South China Sea has been identified as another source of potential tsunamigenic earthquakes that might trigger large tsunamis. To protect coastal communities that might be affected by future tsunamis, an effective early warning system must be properly installed and maintained to provide adequate time for residents to be evacuated from risk zones. Affected communities must be prepared and educated in advance regarding tsunami risk zones, evacuation routes as well as an effective evacuation procedure that must be taken during a tsunami occurrence. For these purposes, tsunami risk zones must be identified and classified according to the levels of risk simulated. This paper presents an analysis of tsunami simulations for the South China Sea and the Andaman Sea for the purpose of developing a tsunami risk zone classification map for Malaysia based upon simulated maximum wave heights. Keywords: tsunami risk simulation, early warning system.

Conference Paper↗
USGS2008

Diverse deformation patterns of Aleutian volcanoes from InSAR

Interferometric synthetic aperture radar (InSAR) is capable of measuring ground-surface deformation with centimeter-to-subcentimeter precision at a spatial resolution of tens of meters over an area of hundreds to thousands of square kilometers. With its global coverage and all-weather imaging capability, InSAR has become an increasingly important measurement technique for constraining magma dynamics of volcanoes over remote regions such as the Aleutian Islands. The spatial pattern of surface deformation data derived from InSAR images enables the construction of detailed mechanical models to enhance the study of magmatic processes. This paper summarizes the diverse deformation patterns of the Aleutian volcanoes observed with InSAR and demonstrates that deformation patterns and associated magma supply mechanisms in the Aleutians are diverse and vary between volcanoes. These findings provide a basis for improved models and better understanding of magmatic plumbing systems.

Conference Paper↗
USGS1985

EARTHQUAKE PERFORMANCE OF A BRIDGE DECK AND ABUTMENT.

During the 24 April 1984 Morgan Hill Earthquake (M equals 6. 1), 15 channels of acceleration records were obtained at the site of the I-280-680/US 101 interchange 12 km west of the epicenter. These records include free field measurements as well as the acceleration response at one of the supporting column bases, and at three locations in one of the spans of the three-span continuous post-tensioned box-girder deck. The purpose of this paper is to review the performance of this bridge deck and its abutment through the study of these records. The objective in extensively instrumenting a bridge deck or any structure is to obtain relevant response data to study its behaviour during strong motion events and ultimately extrapolate conclusions for improved design.

Conference Paper↗