Publications

The crustal and upper mantle compressional-wave velocity structure across the southwestern Arabian Shield has been investigated by a 1000-km-long seismic refraction profile. The profile begins in Mesozoic cover rocks near Riyadh on the Arabian Platform, trends southwesterly across three major Precambrian tectonic provinces, traverses Cenozoic rocks of the coastal plain near Jizan, and terminates a

No abstract available.

A 100×40 km trilateration network extending from Bishop, California, to near Hawthorne, Nevada, crosses the east end of the Long Valley caldera, site of renewed magma inflation in the 1979–1980 interval, and spans most of the White Mountain seismic gap. The network was surveyed in 1972, 1973, 1976, 1979, 1980, and 1982. The 1980 survey may be contaminated by a scale error. In addition, leveling su

The 1982–1983 deformation observed by trilateration and leveling surveys across the Long Valley caldera is apparently related to the 8.5‐km‐long by 8‐km‐deep vertical rupture surface defined by the January 1983 earthquake swarm that occurred in the south moat of the caldera. The observed deformation can be explained as follows. In late 1982, 0.03 km3 of magma was injected into a dike that dips 30°

The Tehachapi trilateration network spans the intersection of the San Andreas and Garlock faults in southern California in the “Big Bend” region of the San Andreas fault. Analysis of data from 1973–1983 shows strain differences between the northwest and southeast regions of the network and slip at depth on both faults. The Palmdale network, spanning the San Andreas fault entirely within the Tehach

A comparative ground response study at sites in the Los Angeles region is based on the extensive strong-motion data set recorded in the 1971 San Fernando earthquake and 159 three-component recordings of distant nuclear tests in Nevada. Amplitude spectral ratios computed for the nuclear test data over those frequency bands for which there is an adequate signal-to-noise ratio provide statistically s

No abstract available.

A 275‐km‐long reversed refraction profile in the Oregon Cascades, two shallow earthquakes of magnitude 5 in southern Washington, a shallow earthquake of magnitude 4.6 in northern California, and a previously published analysis of the Bouguer gravity field are used to develop a crustal P wave velocity model for the Oregon Cascades. Travel time analysis of the refraction profile indicates a crustal

No abstract available.

The U.S. Geological Survey conducted an extensive seismic refraction survey in the Imperial Valley region of California in 1979. The Imperial Valley is located in the Salton Trough, an active rift between the Pacific and North American plates. Forty shots fired at seven shot points were recorded by 100 portable seismic instruments at typical spacing of 0.5–1 km. More than 1300 recording locations

The important role of pore pressure in promoting such brittle processes as cataclasis, hydraulic fracturing, large‐scale faulting, and earthquakes within the crust is widely accepted in geology and geophysics [, 1957; , 1959; , 1958; ., 1963; , 1968; ., 1968; ., 1976; , 1973, 1980; , 1981]. Provided that fluid pressure is fully communicated with rock pore space, the effective normal stresses that

Crystallographically oriented single‐crystal prisms of gem quality topaz (composition AlSiO (OH− F) where x = 0.04 ± 0.01) were deformed at a confining pressure of 1.50 GPa, a temperature of 800°C, and a strain rate of 2×10 s. Under nearly identical conditions, all crystals of anhydrous rock‐forming minerals that have been tested to date, such as olivine, quartz, feldspars, pyroxenes, and refracto