Publications

Accurate characterization of fractured‐rock aquifer heterogeneity remains one of the most challenging and important problems in groundwater hydrology. We demonstrate a promising strategy to identify preferential flow paths in fractured rock using a combination of geophysical monitoring and conventional hydrogeologic tests. Cross‐well difference‐attenuation ground‐penetrating radar was...

Diffraction tomography imaging was applied to VRP data acquired by vertically moving a receiving antenna in a number of wells. This procedure simulated a vertical downhole receiver array. Similarly, a transmitting antenna was sequentially moved along a series of radial lines extending outward from the receiver wells. This provided a sequence of multistatic data sets and, from each data...

This document describes the MOD-PREDICT program, which helps evaluate userdefined sets of observations, prior information, and predictions, using the ground-water model MODFLOW-2000. MOD-PREDICT takes advantage of the existing Observation and Sensitivity Processes (Hill and others, 2000) by initiating runs of MODFLOW-2000 and using the output files produced. The names and formats of the...

This publication contains the abstracts and program for the workshop on complex systems that was held on November 19-21, 2002, in Reno, Nevada. Complex systems are ubiquitous within the realm of the earth sciences. Geological systems consist of a multiplicity of linked components with nested feedback loops; the dynamics of these systems are non-linear, iterative, multi-scale, and operate...

Most geologic maps published for central California in the past century have been made without the benefit of microfossils. The age of Cretaceous and Tertiary rocks in the structurally complex sedimentary formations of the Coast Ranges is critical in determining stratigraphic succession and in determining whether the juxtapositon of similar appearing formations means that a fault is...

A belt of Paleogene near-trench plutons known as the Sanak-Baranof belt intruded the southern Alaska convergent margin. A compilation of isotopic ages of these plutons shows that they range in age from 61 Ma in the west to ca. 50 Ma in the east. This migrating pulse of magmatism along the continental margin is consistent with North Pacific plate reconstructions that suggests the plutons...

Borehole radar can be used in a single-hole reflection mode or in a cross-hole tomography mode. In the reflection mode, radar provides an image of discontinuities in the bedrock surrounding a borehole, including bedding planes, lithologic contacts, fractures, and cavities. The measurements are either directional or omni-directional, depending upon the type of equipment and antennas. In...

The U.S. Geological Survey (USGS), in cooperation with United Technologies Corporation, used an integrated suite of borehole, surface, and water-borne geophysical methods near the site of the former Winthrop Landfill, Winthrop, Maine, to investigate the hydrogeology controlling the transport of leachate from the landfill to nearby Annabessacook Lake. During the fall of 2000 and summer of...

No abstract available.

A concerted effort is underway to prepare a substantially upgraded digital gravity anomaly database for the United States and to make this data set and associated usage tools available on the internet. This joint effort, spearheaded by the geophysics groups at the National Imagery and Mapping Agency (NIMA), University of Texas at El Paso (UTEP), U.S. Geological Survey (USGS), and...

The digital dataset consists of one file (monterey_100k.iso) containing 2,385 gravity stations. The file, monterey_100k.iso, contains the principal facts of the gravity stations, with one point coded per line. The format of the data is described below. Each gravity station has a station name, location (latitude and longitude, NAD27 projection), elevation, and an observed gravity reading...

Clear Creek, one of the major tributaries of the upper Sacramento River, drains the eastern Trinity Mountains. Alluvial plain and terrace gravels of lower Clear Creek, at the northwest edge of the Sacramento Valley, contain placer gold that has been mined since the Gold Rush by various methods including dredging. In addition, from the 1950s to the 1980s aggregate-mining operations...