Publications

Maps of northern and southern California printed on flyleaf inside front cover and on adjacent pages show faults that have had displacement within the past 2 million years. Those that have had displacement within historical time are shown in red. Bands of red tint emphasize zones of historical displacement; bands of orange tint emphasize major faults that have had Quaternary displacement...

No abstract available.

The attenuation of upper crustal seismic waves that are refracted with a velocity of about 6 kilometers per second varies greatly among profiles in the area of the New Madrid seismic zone in the central Mississippi Valley. The waves that have the strongest attenuation pass through the seismic trend along the axis of the Reelfoot rift in the area of the Blytheville arch. Defocusing of the...

Several regional seismic refraction and magnetotelluric (MT) profiles have been completed across the Cascade Range and surrounding geologic provinces in California, Oregon, and Washington. Analysis of three MT and two seismic refraction profiles in Oregon and a coincident MT and refraction profile in northern California show a high degree of correlation between resistivity and velocity...

A portion of northwestern Nevada was imaged to determine the crustal structure and to assess reported differences between refraction versus reflection determinations of Moho depth and how the crustal composition and structure has been influenced by volcanic and extension mechanisms. Interpretation of the refraction/wide-angle reflection data suggests that the crust is fairly uniform in...

A seismic refraction profile recorded along the geologic strike of the Chugach Mountains in southern Alaska shows three upper crustal high‐velocity layers (6.9, 7.2, and 7.6 km/s) and a unique pattern of strongly focussed echelon arrivals to a distance of 225 km. The group velocity of the ensemble of echelon arrivals is 6.4 km/s. Modeling of this profile with the reflectivity method...

Significant progress has been made over the past five decades in determining the geophysical framework of the continental United States. Highlights include detailed maps of gravity and aeromagnetic anomalies, heat flow, crustal thickness, seismicity, state of stress, and paleomagnetic pole positions. Important tectonic insights have come from earthquake studies, and from knowledge of...

The Pacific Coastal States form a complex geologic environment in which the crust and lithosphere have been continuously reworked. We divide the region tectonically into the southern transform regime of the San Andreas fault and the northern subduction regime, and summarize the geophysical framework with contour maps of crustal thickness, lithospheric and seismicity cross sections, and...

The seismologic methods most commonly used in studies of earthquakes and the structure of the continental lithosphere are reviewed in three main sections: earthquake source parameter determinations, the determination of earth structure using natural sources, and controlled-source seismology. The emphasis in each section is on a description of data, the principles behind the analysis...

No abstract available.

The frictional strength of ice seems to be well below that for all other rocks. Triaxial testing of cylinders of pure water ice containing a 45° inclined sawcut, at temperatures of 77 ≤ T ≤ 115 K and confining pressures 0.1 ≤ P ≤ 250 MPa, reveals the frictional laws τ = 0.20 σn + 8.3 MPa for P ≥ 10 MPa and τ = 0.55 σn + 1.0 MPa for P ≤ 5 MPa, where τ and σn are the shear and normal...

Crustal velocity sections based on two seismic-refraction profiles are presented for the area west of Yucca Mountain, Nye County, Nevada. The Crater Flat profile is interpreted in terms of six velocity layers ranging from 1.5 to 6.1 km/s. Interpretation of the Beatty profile reveals an escarpment near the northeast edge of Bare Mountain, where Paleozoic rocks are probably down-faulted...