Publications

Subduction zone megathrust faults produce most of the world’s largest earthquakes. Although the physical properties of these faults are difficult to observe directly, their frictional strength can be estimated indirectly by constraining the orientations of the stresses that act on them. A global investigation of stress orientations in subduction zones finds that the maximum compressive...

Detailed geodetic imaging of earthquake rupture enhances our understanding of earthquake physics and induced ground shaking. The April 25, 2015 Mw 7.8 Gorkha, Nepal earthquake is the first example of a large continental megathrust rupture beneath a high-rate (5 Hz) GPS network. We use GPS and InSAR data to model the earthquake rupture as a slip pulse of ~20 km width, ~6 s duration, and...

The Mediterranean region is seismically active due to the convergence of the Africa Plate with the Eurasia plate. Present day Africa-Eurasia motion ranges from ~4 millimeters per year (mm/yr) in a northwest-southeast direction in the western Mediterranean to ~10 mm/yr (north-south) in the eastern Mediterranean. The Africa-Eurasia plate boundary is complex, and includes extensional and

Three broadband simulation methods are used to generate synthetic ground motions for the 2011 Mineral, Virginia, earthquake and compare with observed motions. The methods include a physics‐based model by Hartzell et al. (1999, 2005), a stochastic source‐based model by Boore (2009), and a stochastic site‐based model by Rezaeian and Der Kiureghian (2010, 2012). The ground‐motion dataset...

Mount St. Helens began erupting in late 2004 following an 18 year quiescence. Swarms of repeating earthquakes accompanied the extrusion of a mostly solid dacite dome over the next 4 years. In some cases the waveforms from these earthquakes evolved slowly, likely reflecting changes in the properties of the volcano that affect seismic wave propagation. We use coda-wave interferometry to...

The Frazier Mountain paleoseismic site is located within the northern Big Bend of the southern San Andreas Fault (lat 34.8122° N., lon 118.9034° W.), in a small structural basin formed by the fault (fig. 1). The site has been the focus of over a decade of paleoseismic study due to high stratigraphic resolution and abundant dateable material. Trench 1 (T1) was initially excavated as a 50...

No abstract available.

We make use of the most recent National Seismic Hazard Maps (the years 2008 and 2014 cycles), updated census data on population, and economic exposure estimates of general building stock to quantify annualized earthquake loss (AEL) for the conterminous United States. The AEL analyses were performed using the Federal Emergency Management Agency's (FEMA) Hazus software, which facilitated a

No abstract available.

We report on the development and validation of an algorithm for estimating geoelectric fields induced in the lithosphere beneath an observatory during a magnetic storm. To accommodate induction in three-dimensional lithospheric electrical conductivity, we analyze a simple nine-parameter model: two horizontal layers, each with uniform electrical conductivity properties given by...

Landslides into valley bottoms can affect longitudinal profiles of rivers, thereby influencing landscape evolution through base-level changes. Large landslides can hinder river incision by temporarily damming rivers, but catastrophic failure of landslide dams may generate large floods that could promote incision. Dam stability therefore strongly modulates the effects of landslide dams...

For decades, scientists have probed Earth's remote mantle by analyzing how seismic waves of distant earthquakes pass through it. But we are still challenged by the technique's limitations.