Publications

When a powerful earthquake strikes an urban region, damage concentrates not only near the quake's source. Damage can also occur many miles from the source in areas of soft ground. In recent years, scientists have developed ways to identify and map these areas of high seismic hazard. This advance has spurred pioneering legislation to reduce earthquake losses in areas of greatest hazard.

Almost 75 percent of Utah's population lives near the Wasatch Fault. Earth scientists have shown that this fault has repeatedly experienced strong earthquakes of magnitude 7 or larger and will continue to do so in the future. Efforts to increase public awareness of earthquake hazards in Utah have resulted in residents and community leaders taking actions that will save lives and reduce damage in f

No abstract available.

We are leading a new international initiative to conduct scientific drilling within the San Andreas fault zone at depths of up to 10 km. This project is motivated by the need to understand the physical and chemical processes operating within the fault zone and to answer fundamental questions about earthquake generation along major plate-boundary faults. Through a comprehensive program of coring, f

Strain accumulation observed over the 1978–1991 interval in a 30×100 km aperture trilateration network spanning the Laguna Salada fault is described by the principal strain rates 0.101±0.012 strain/yr N80°E±2° and −0.021±0.012 strain/yr N10°W±2°, extension reckoned positive. These strain accumulation rates have been corrected to remove coseismic effects of the nearby 1979 Imperial Valley ( = 6.5),

Postseismic deformation along a 90‐km profile bisecting the projected surface trace of the coseismic rupture of the 1989 Loma Prieta earthquake has been monitored by frequent GPS surveys for 3.3 years following the earthquake. In addition to the expected deformation associated with secular strain accumulation on the San Andreas and Calaveras faults, deformation associated with postseismic readjust

No significant change in the rate of strain accumulation in a 40×120 km trilateration network spanning the San Gabriel mountains was observed from 1977.5 to 1991.8 despite an apparent increase in seismicity (ML > 4.5) beginning in late 1987 in the northern Los Angeles basin immediately to the south. The observed deformation (0.13±0.01 µstrain/yr right‐lateral shear across a vertical plane striking

No abstract available. 

Recent borehole-geotechnical data and strong-motion measurements constitute a new empirical basis to account for local geological conditions in earthquake-resistant design and site-dependent, building-code provisions. They provide new unambiguous definitions of site classes and rigorous empirical estimates of site-dependent amplification factors in terms of mean shear-wave velocity. A simple four-

Several recent models of crustal evolution are based on the belief that the thickness of the continental crust is proportional to its age, with ancient crust being the thickest. A worldwide review of seismic structure contradicts this belief and falsifies these models, at least for the Archean. Proterozoic crust has a thickness of 40–55 km and a substantial high‐velocity (>7 km/s) layer at its bas

The Fairbanks North seismic refraction/ wide-angle reflection profile, collected by the U.S. Geological Survey Trans-Alaska Crustal Transect (TACT) project in 1987, crosses the complex region between the Yukon-Tanana and Ruby terranes in interior Alaska. This region is occupied by numerous small terranes elongated in a northeast-southwest direction. These seismic data reveal a crustal velocity str

The P- and S-wave arrivals from local earthquakes were studied using an array of 10 three-component instruments in and around a tunnel at Garni Observatory, Armenia. The array has a three-dimensional configuration with lateral dimensions of 300 to 500 m and a depth extent of 100 m. Estimates of the horizontal and vertical components of slowness for P and S wave fronts were used to determine the an