Publications

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Most models of lower crust/mantle viscosity inferred from postearthquake relaxation assume one or two uniform-viscosity layers. A few existing models possess apparently significant radially variable viscosity structure in the shallow mantle (e.g., the upper 200 km), but the resolution of such variations is not clear. We use a geophysical inverse procedure to address the resolving power...

Of methods for measuring temporal changes in seismic-wave speeds in the Earth, seismic tomography is among those that offer the highest spatial resolution. 3-D tomographic methods are commonly applied in this context by inverting seismic wave arrival time data sets from different epochs independently and assuming that differences in the derived structures represent real temporal...

The formation, evolution, collapse, and subsequent resurrection of a vent within Halema'uma'u Crater, Kilauea Volcano, produced energetic and varied degassing signals recorded by a nearby infrasound array between 2008 and early 2009. After 25 years of quiescence, a vent-clearing explosive burst on 19 March 2008 produced a clear, complex acoustic signal. Near-continuous harmonic...

We invert peak ground velocity and acceleration (PGV and PGA) to estimate rupture direction and rupture velocity for 47 moderate earthquakes (3.5≥M≥5.4) in northern California. We correct sets of PGAs and PGVs recorded at stations less than 55–125 km, depending on source depth, for site amplification and source–receiver distance, then fit the residual peak motions to the unilateral...

Statistical seismology is the application of rigorous statistical methods to earthquake science with the goal of improving our knowledge of how the earth works. Within statistical seismology there is a strong emphasis on the analysis of seismicity data in order to improve our scientific understanding of earthquakes and to improve the evaluation and testing of earthquake forecasts...

Geophysical Research Letters (GRL) is the American Geophysical Union's premier journal of fast, groundbreaking communication. It rapidly publishes high- impact,letter-length articles, and it is the top-cited multidisciplinary geosciences journal over the past 10 years, with an impact factor that increased again in 2009, to 3.204. For manuscripts submitted to GRL, the median time to first...

We determined the stress parameter, Δσ, for the eight earthquakes studied by Atkinson and Boore (2006), using an updated dataset and a revised point-source stochastic model that captures the effect of a finite fault. We consider four geometrical-spreading functions, ranging from 1/R at all distances to two- or three-part functions. The Δσ values are sensitive to the rate of geometrical...

The October 3, 2009 (01:16:00 UTC), Olancha M5.2 earthquake caused extensive liquefaction as well as permanent horizontal ground deformation within a 1.2 km2area earthquake in Owens Valley in eastern California (USA). Such liquefaction is rarely observed during earthquakes of M ≤ 5.2. We conclude that subsurface conditions, not unusual ground motion, were the primary factors contributing...

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...

We analyzed mortality rates of earthquakes worldwide and developed a country/region-specific empirical model for earthquake fatality estimation within the U.S. Geological Survey's Prompt Assessment of Global Earthquakes for Response (PAGER) system. The earthquake fatality rate is defined as total killed divided by total population exposed at specific shaking intensity level. The total...

The earthquake engineering profession is increasingly utilizing nonlinear response history analyses (RHA) to evaluate seismic performance of existing structures and proposed designs of new structures. One of the main ingredients of nonlinear RHA is a set of ground-motion records representing the expected hazard environment for the structure. When recorded motions do not exist (as is the...