Publications

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...

An important discovery in crustal mechanics has been that the Earth’s crust is commonly stressed close to failure, even in tectonically quiet areas. As a result, small natural or man-made perturbations to the local stress field may trigger earthquakes. To understand these processes, Passive Seismic Monitoring (PSM) with seismometer arrays is a widely used technique that has been...

Earthquakes on strike-slip faults can produce devastating natural hazards. However, because they consist predominantly of lateral motion, these faults are rarely associated with significant uplift or tsunami generation. And although submarine slides can generate tsunami, only a few per cent of all tsunami are believed to be triggered in this way. The 12 January Mw 7.0 Haiti earthquake...

In a comment on our 2008 paper (Catchings, Gandhok, et al., 2008) on the Santa Monica fault in Los Angeles, California, Pratt and Dolan (2010) (herein referred to as P&D) cite numerous objections to our work, inferring that our study is flawed. However, as shown in our reply, their objections contradict their own published works, published works of others, and proven seismic...

Remote sensing instruments aboard the Cassini spacecraft have been observed the surface of Titan globally in the infrared and radar wavelength ranges as well as locally by the Huygens instruments revealing a wealth of new morphological features indicating a geologically active surface. We present a summary of mapping products of Titan's surface derived from data of the remote sensing...

U-series dating of pedogenic carbonate-clast coatings provides a reliable, precise minimum age of 45.1 ± 0.6 ka (2σ) for the T2 geomorphic surface of the Biskra Palms alluvial fan, Coachella Valley, California. Concordant ages for multiple subsamples from individual carbonate coatings provide evidence that the 238U-234U-230Th system has remained closed since carbonate formation. The U...

Understanding the performance of sensors and recorders is prerequisite to making appropriate use of them in seismology and earthquake engineering. This paper explores a critical aspect of instrument performance, the “self” noise level of the device and the amplitude range it can usefully record. Self noise limits the smallest signals, while instrument clipping level creates the upper...

The upper mantle of North America has been well studied using various seismic methods. Here we investigate the density structure of the North American (NA) upper mantle based on the integrative use of the gravity field and seismic data. The basis of our study is the removal of the gravitational effect of the crust to determine the mantle gravity anomalies. The effect of the crust is...

In March of 2010, the U.S. Geological Survey (USGS) conducted geophysical surveys east of Cat Island, Mississippi (fig. 1). The efforts were part of the USGS Gulf of Mexico Science Coordination partnership with the U.S. Army Corps of Engineers (USACE) to assist the Mississippi Coastal Improvements Program (MsCIP) and the Northern Gulf of Mexico (NGOM) Ecosystem Change and Hazards...

It has been 153 yr since the last large earthquake on the southern San Andreas fault (California, United States), but the average interseismic interval is only ~100 yr. If the recurrence of large earthquakes is periodic, rather than random or clustered, the length of this period is notable and would generally increase the risk estimated in probabilistic seismic hazard analyses...