Publications

New measures of spectral intensity based on the horizontal components of ground shaking are introduced. These new measures are independent of the in situ orientation of the recordings and encompass the full range of spectral amplitudes over all possible rotation angles. Unlike previously introduced measures that are also orientation independent, no geometric means are used in the...

It has been proposed that the crustal stress field contains small-length-scale heterogeneity of much larger amplitude than the uniform background stress. This model predicts that earthquake focal mechanisms should reflect the loading stress rather than the uniform background stress. So, if the heterogeneous stress hypothesis is correct, focal mechanisms before and after a large...

Data points represent head scarps, flank scarps, and minor internal scarps (linear) associated with landslide deposits in the Little North Santiam River Basin, Oregon. This work was completed as part of the Master's thesis "Turbidity Monitoring and LiDAR Imagery Indicate Landslides are Primary Source of Suspended-Sediment Load in the Little North Santiam River Basin, Oregon, Winter 2009...

The structural geology of an outcropping of layered sedimentary deposits in southwest Candor Chasma is mapped using two adjacent high-resolution (1 m/pixel) HiRISE digital elevation models and orthoimagery. Analysis of these structural data yields new insight into the depositional and deformational history of these deposits. Bedding in non-deformed areas generally dips toward the center...

The water table is a fundamental concept in hydrogeology, yet it is frequently incorrectly defined. For example, both the NGWA (2003) and AGI (Neuendorf et al. 2005) glossaries define the water table as the atmospheric pressure surface that is coincident with the top of the zone of saturation. This definition is also found occasionally in groundwater textbooks as well as in primers...

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No abstract available.

Serpentinized ophiolitic rocks are juxtaposed against quartzofeldspathic rocks at depth across considerable portions of the Hayward and Calaveras Faults. The marked compositional contrast between these rock types may contribute to fault creep that has been observed along these faults. To investigate this possibility, we are conducting hydrothermal shearing experiments to look for changes...

We examined elevation changes detected from two successive sets of Light Detection and Ranging (LiDAR) data in the northern Coast Range of Oregon. The first set of LiDAR data was acquired during leafon conditions and the second set during leaf-off conditions. We were able to successfully identify and map active landslides using a differential digital elevation model (DEM) created from...

The morphologies of some martian gullies appear similar to terrestrial features associated with debris flow initiation, erosion, and deposition. On Earth, debris flows are often triggered by shallow subsurface throughflow of liquid water in slope-mantling colluvium. This flow causes increased levels of pore pressure and thus decreased shear strength, which can lead to slide failure of...

An AGU Chapman Conference commemorated the fiftieth anniversary of the 1960 M 9.5 Chile earthquake. Participants reexamined this earthquake, the largest ever recorded instrumentally, and compared it with Chile's February 2010 M 8.8 earthquake. They also addressed the giant earthquake potential of subduction zones worldwide and strategies for reducing losses due to tsunamis. The...

The influence of the 08 October 2005 Kashmir earthquake and subsequent snow melt and monsoon rainfall on slope stability was evaluated using repeat photography in the Kashmir Himalaya of northern Pakistan. Sixty-eight landslide-affected locations were selected and photographed in November 2005, May/June 2006, June 2007, and August 2007 to evaluate all potential geomorphic changes. Eighty...