Publications

During the MW 7.1 Hector Mine earthquake, peak ground velocities recorded at sites in the central San Bernardino basin region were up to 2 times larger and had significantly longer durations of strong shaking than sites just outside the basin. To better understand the effects of 3D structure on the long-period ground-motion response in this region, we have performed finite-difference...

Chronosequential analysis of soil properties has proven to be a valuable approach for estimating ages of geomorphic surfaces where no independent age control exists. In this study we examined pedogenic silica as an indicator of relative ages of soils and geomorphic surfaces, and assessed potential sources of the silica. Pedogenic opaline silica was quantified by tiron (4,5-dihydroxy-1,3...

Peels made from 10 geoslices beneath a riverbank at Washington's Hunting Island, 45 km inland from the Pacific coast, aid in identifying sand that liquefied during prehistoric earthquakes of estimated magnitude 8-9 at the Cascadia subduction zone. Each slice was obtained by driving sheetpile and a shutter plate to depths of 6-8 m. The resulting sample, as long as 8 m, had a trapezoidal...

This study is devoted to a systematic analysis of the state of stress of the central European Alps and northern Alpine foreland in Switzerland based on focal mechanisms of 138 earthquakes with magnitudes between 1 and 5. The most robust feature of the results is that the azimuth of the minimum compressive stress, S3, is generally well constrained for all data subsets and always lies in...

When raised to temperatures above the ice melting point, gas hydrates release their gas in well-defined, reproducible events that occur within self-maintained temperature ranges slightly below the ice point. This behavior is observed for structure I (carbon dioxide, methane) and structure II gas hydrates (methane-ethane, and propane), including those formed with either H2O- or D2O-host...

No abstract available.

The Tien Shan orogenic belt is the most active intracontinental mountain belt in the world. We describe an 86-km-long N–S-trending deep seismic reflection profile (which passes through the southern Junggar basin) located on the northeastern Tien Shan piedmont. Two distinct anticlines beneath the northern margin of the Tien Shan are clearly imaged in the seismic section. In addition, we...

We present photomosaics and logs of the walls of trenches excavated for a paleoseismic study at Thousand Palms Oasis (Fig. 1). The site is located on the Mission Creek strand of the San Andreas fault zone, one of two major active strands of the fault in the Indio Hills along the northeast margin of the Coachella Valley (Fig. 2). The Coachella Valley section is the most poorly understood...

We present photomosaics and logs of the walls of trenches excavated for a paleoseismic study at Arano Flat, one of two sites along the San Andreas fault in the Santa Cruz Mountains on the Kelley-Thompson Ranch. At this location, the fault consists of a narrow zone along the northeast side of a low ridge adjacent to a possible sag pond and extends about 60-70 meters across a broad...

The Earth's topography at short wavelengths results from active tectonic processes, whereas at long wavelengths it is largely determined by isostatic adjustment for the density and thickness of the crust. Using a global crustal model, we estimate the long-wavelength topography that is not due to crustal isostasy. Our most important finding is that cratons are generally depressed by 300...

Most of the geologic maps published for central California before 1960 were made without the benefit of age determinations from microfossils. The ages of Cretaceous and Tertiary rocks in the mostly poorly exposed and structurally complex sedimentary rocks represented in the Coast Ranges are critical in determining stratigraphic succession or lack of it, and in determining whether the...

Most procedures for routinely locating earthquake hypocenters within a local network are constrained to using laterally homogeneous velocity models to represent the Earth's crustal velocity structure. As a result, earthquake location errors may arise due to actual lateral variations in the Earth's velocity structure. Station corrections can be used to compensate for heterogeneous...