Publications

Redoubt Volcano, an ice-covered stratovolcano on the west side of Cook Inlet, erupted in March 2009 after several months of escalating unrest. The 2009 eruption of Redoubt Volcano shares many similarities with eruptions documented most recently at Redoubt in 1966–68 and 1989–90. In each case, the eruptive phase lasted several months, consisted of multiple ashproducing explosions...

Hotspot: The Snake River Geothermal Drilling Project was undertaken to better understand the geothermal systems in three locations across the Snake River Plain with varying geological and hydrological structure. An extensive series of standard and specialized geophysical logs were obtained in each of the wells. Hydrogen-index neutron and γ-γ density logs employing active sources were...

When an earthquake occurs, the U. S. Geological Survey (USGS) ShakeMap estimates the extent of potentially damaging shaking and provides overall information regarding the affected areas. The USGS ShakeCast system is a freely-available, post-earthquake situational awareness application that automatically retrieves earthquake shaking data from ShakeMap, compares intensity measures against...

[1] Analysis is made of the geomagnetic-activityaaindex covering solar cycle 11 to the beginning of 24, 1868–2011. Autocorrelation shows 27.0-d recurrent geomagnetic activity that is well-known to be prominent during solar-cycle minima; some minima also exhibit a smaller amount of 13.5-d recurrence. Previous work has shown that the recent solar minimum 23–24 exhibited 9.0 and 6.7-d...

In September 2010, the USGS began publicly releasing earthquake alerts for significant earthquakes around the globe based on estimates of potential casualties and economic losses with its Prompt Assessment of Global Earthquakes for Response (PAGER) system. These estimates significantly enhanced the utility of the USGS PAGER system which had been, since 2006, providing estimated...

The 23 August 2011 Mineral, Virginia, earthquake (Mw 5.8) was the largest to strike the eastern U.S. since 1897 and was felt over an extraordinarily large area. Although no large landslides occurred, the shaking did trigger many rock and soil falls from steep river banks and natural cliffs in the epicentral area and from steep road cuts along, and northwest of, the Blue Ridge Parkway. We...

The widely held perception that the San Andreas fault (SAF) is vertical or steeply dipping in most places in southern California may not be correct. From studies of potential‐field data, active‐source imaging, and seismicity, the dip of the SAF is significantly nonvertical in many locations. The direction of dip appears to change in a systematic way through the Transverse Ranges...

The Grizzly Valley fault system (GVFS) strikes northwestward across Sierra Valley, California and is part of a network of active, dextral strike-slip faults in the northern Walker Lane (Figure 1). To investigate Quaternary motion across the GVFS, we analyzed high-resolution (0.25 m) airborne LiDAR data (Figure 2) in combination with six, high-resolution, P-wave, seismic-reflection...

Titan's fluvial channels have been investigated based on data obtained by the Synthetic Aperture Radar (SAR) instrument and the Visible and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft. In this paper, a database of fluvial features is created based on radar-SAR data aiming to unveil the distribution and the morphologic and spectral characteristics of valleys on...

We sampled fumaroles and hot springs from the Heart Lake Geyser Basin (HLGB), measured water and gas discharge, and estimated heat and mass flux from this geothermal area in 2009. The combined data set reveals that diverse fluids share an origin by mixing of deep solute-rich parent water with dilute heated meteoric water, accompanied by subsequent boiling. A variety of chemical and...

Using Dawn’s Gamma Ray and Neutron Detector, we tested models of Vesta’s evolution based on studies of howardite, eucrite, and diogenite (HED) meteorites. Global Fe/O and Fe/Si ratios are consistent with HED compositions. Neutron measurements confirm that a thick, diogenitic lower crust is exposed in the Rheasilvia basin, which is consistent with global magmatic differentiation. Vesta’s...

U.S. national building codes refer to the ASCE/SEI-7 provisions for selecting and scaling ground motions for use in nonlinear response history analysis of structures. Because the limiting values for the number of records in the ASCE/SEI-7 are based on engineering experience, this study examines the required number of records statistically, such that the scaled records provide accurate...