Publications

The largest-magnitude earthquake in the past 20 years struck near Mt. Carmel in southeastern Illinois on Friday morning, 18 April 2008 at 09:36:59 UTC (04:37 CDT). The Mw 5.2 earthquake was felt over an area that spanned Chicago and Atlanta, with about 40,000 reports submitted to the U.S. Geological Survey (USGS) “Did You Feel It?” system. There were at least six felt aftershocks greater...

No abstract available.

We have developed a community velocity model for the Pacific Northwest region from northern California to southern Canada and carried out the first 3D simulation of a Mw 9.0 megathrust earthquake rupturing along the Cascadia subduction zone using a parallel supercomputer. A long-period (

The Sonora, Mexico, earthquake of 3 May 1887 occurred a few years before the start of the instrumental era in seismology. We revisit all available accounts of the earthquake and assign Modified Mercalli Intensities (MMI), interpreting and analyzing macroseismic information using the best available modern methods. We find that earlier intensity assignments for this important earthquake...

[1] Perfettini and Avouac (2004) postulated that both the aftershock rate (assumed proportional to the local stressing rate) and the postseismic relaxation are driven by the loading imposed by postseismic slip on the brittle creep fault zone (BCFZ), the downdip extension of the fault zone below the coseismic rupture. I explore the consequences of that hypothesis for a long, strike-slip...

The M6.6 mainshock of the Niigata Chuetsu Oki (offshore) earthquake occurred at 10:13 a.m. local time on July 16, 2007, and was followed by a sequence of aftershocks that were felt during the entire time of the reconnaissance effort. The mainshock had an estimated focal depth of 10 km and struck in the Japan Sea offshore Kariwa. Analysis of waveforms from source inversion studies...

Introduction Our purpose is to update with six additional years of data, our creep data archive on San Francisco Bay region active faults for use by the scientific research community. Earlier data (1979-2001) were reported in Galehouse (2002) and were analyzed and described in detail in a summary report (Galehouse and Lienkaemper, 2003). A complete analysis of our earlier results...

In support of earthquake hazards and ground motion studies in the Pacific Northwest, three-dimensional P- and S-wave velocity (3D Vp and Vs) and density (3D rho) models incorporating the Cascadia subduction zone have been developed for the region encompassed from about 40.2°N to 50°N latitude, and from about -122°W to -129°W longitude. The model volume includes elevations from 0 km to 60...

Introduction Although effects of rotational motions due to earthquakes have long been observed (e. g., Mallet, 1862), nevertheless Richter (1958, p. 213) stated that: 'Perfectly general motion would also involve rotations about three perpendicular axes, and three more instruments for these. Theory indicates, and observation confirms, that such rotations are negligible.' However, Richter...

The U.S. Geological Survey (USGS), established by an act of Congress in 1879, is the Nation's largest natural science and civilian mapping agency. The USGS works in cooperation with more than 2,000 organizations across the country to provide reliable, impartial scientific information. This information is used to minimize the loss of life and property from natural disasters, safeguard the...

The layer-structure minerals serpentine, brucite, and talc are postulated to form in the mantle wedge above a subducting slab as a result of progressive hydration and silica metasomatism. Tectonic mixing at the slab-mantle interface generates serpentinite mélanges that contain blocks of high-pressure (HP) or ultrahigh-pressure (UHP) metamorphic rock derived from the subducting slab. Such

INTRODUCTION An active rockslide in Merced River Canyon was first noticed on April 29, 2006 when a few rocks rolled onto Highway 140 between mileposts 103 and 104, compromising traffic on this highway and signaling the onset of renewed activity of the Ferguson rockslide. State highway 140 is one of the main entrances to Yosemite National Park and is the primary road for large commercial...