Publications
Filter Total Items: 2585
Steep-dip seismic imaging of the shallow San Andreas Fault near Parkfield
Seismic reflection and refraction images illuminate the San Andreas Fault to a depth of 1 kilometer. The prestack depth-migrated reflection image contains near-vertical reflections aligned with the active fault trace. The fault is vertical in the upper 0.5 kilometer, then dips about 70° to the southwest to at least 1 kilometer subsurface. This dip reconciles the difference between the computed loc
Authors
J.A. Hole, R. D. Catchings, K.C. St. Clair, M. J. Rymer, D. A. Okaya, B.J. Carney
Integrated surface and borehole strong-motion, soil-response arrays in San Francisco, California
An integrated set of four borehole arrays and ten surface installations is installed in the city of San Francisco, California to measure the response of soft-soil deposits to strong earthquake ground motions. The borehole arrays extend through thick layers of softwater-saturated soils of Holocene age and older more consolidated soils of Pleistocene age into bedrock at depths up to 100 m. The surfa
Authors
Roger D. Borcherdt, H. P. Liu, R.E. Westerlund, Christopher M. Dietel, J. F. Gibbs, R. E. Warrick
Seismic hazard in Hawaii: High rate of large earthquakes and probabilistics ground-motion maps
The seismic hazard and earthquake occurrence rates in Hawaii are locally as high as that near the most hazardous faults elsewhere in the United States. We have generated maps of peak ground acceleration (PGA) and spectral acceleration (SA) (at 0.2, 0.3 and 1.0 sec, 5% critical damping) at 2% and 10% exceedance probabilities in 50 years. The highest hazard is on the south side of Hawaii Island, as
Authors
F. W. Klein, A. D. Frankel, C.S. Mueller, R. L. Wesson, P. G. Okubo
Mountain Meadows Dacite: Oligocene intrusive complex that welds together the Los Angeles Basin, northwestern Peninsular Ranges, and central Transverse Ranges, California
Dikes and irregular intrusive bodies of distinctive Oligocene biotite dacite and serially related hornblende latite and felsite occur widely in the central and eastern San Gabriel Mountains, southern California, and are related to the Telegraph Peak granodiorite pluton. Identical dacite is locally present beneath Middle Miocene Topanga Group Glendora Volcanics at the northeastern edge of the Los A
Authors
Thane H. McCulloh, Larry A. Beyer, Ronald W. Morin
Borehole P- and S-wave velocity at thirteen stations in Southern California
The U.S. Geological Survey (USGS), as part of a program to acquire seismic velocity data at locations of strong-ground motion in earthquakes (e.g., Gibbs et al., 2000), has investigated thirteen additional sites in the Southern California region. Of the thirteen sites, twelve are in the vicinity of Whittier, California, and one is located in San Bernardino, California.
Several deployments of temp
Authors
James F. Gibbs, David M. Boore, John C. Tinsley, Charles S. Mueller
Hayward Fault rocks: porosity, density, and strength measurements
Porosity, density and strength measurements were conducted on rock samples collected from the Hayward Fault region in Northern California as part of the Hayward Fault Working Group’s efforts to create a working model of the Hayward Fault. The rocks included in this study were both fine and coarse grained gabbros, altered keratophyre, basalt, sandstone, and serpentinite from various rock formations
Authors
C.A. Morrow, D. A. Lockner
Report for borehole explosion data acquired in the 1999 Los Angeles Region Seismic Experiment (LARSE II), Southern California: Part I, description of the survey
The Los Angeles Region Seismic Experiment (LARSE) is a joint project of the U.S. Geological Survey (USGS) and the Southern California Earthquake Center (SCEC). The purpose of this project is to produce seismic images of the subsurface of the Los Angeles region down to the depths at which earthquakes occur, and deeper, in order to remedy a deficit in our knowledge of the deep structure of this regi
Authors
Gary S. Fuis, Janice M. Murphy, David A. Okaya, Robert W. Clayton, Paul M. Davis, Kristina Thygesen, Shirley A. Baher, Trond Ryberg, Mark L. Benthien, Gerry Simila, J. Taylor Perron, Alan K. Yong, Luke Reusser, William J. Lutter, Galen Kaip, Michael D. Fort, Isa Asudeh, Russell Sell, John R. Van Schaack, Edward E. Criley, Ronald Kaderabek, Will M. Kohler, Nickolas H. Magnuski
High-resolution seismic reflection/refraction images near the outer margin of the Chesapeake Bay impact crater, York-James Peninsula, southeastern Virginia
Powars and Bruce (1999) showed that the Chesapeake Bay region of southeastern Virginia was the site of an asteroid or comet impact during the late Eocene, approximately 35 million years ago (Fig. 1). Initial borehole and marine seismic-reflection data revealed a 90-km-diameter impact structure, referred to as the Chesapeake Bay Impact Crater (CBIC), that lies buried beneath the southern Chesapeake
Authors
R. D. Catchings, D.E. Saulter, D.S. Powars, M. R. Goldman, J.A. Dingler, G. S. Gohn, J. S. Schindler, G.H. Johnson
Implications for the formation of the Hollywood Basin from gravity interpretations of the northern Los Angeles Basin, California
Gravity data provide insights on the complex tectonic history and structural development of the northern Los Angeles Basin region. The Hollywood basin appears to be a long (> 12 km), narrow (up to 2 km wide) trough lying between the Santa Monica Mountains and the Wilshire arch. In the deepest parts of the Hollywood basin, the modeled average thickness ranges from roughly 250 m if filled with only
Authors
Thomas G. Hildenbrand, Jeffrey G. Davidson, Daniel J. Ponti, V. E. Langenheim
By
Natural Hazards Mission Area, Energy and Minerals Mission Area, Earthquake Hazards Program, Energy Resources Program, Mineral Resources Program, National Laboratories Program, Science and Decisions Center, Groundwater and Streamflow Information Program, Earthquake Science Center, Geology, Minerals, Energy, and Geophysics Science Center
How brucite may affect the frictional properties of serpentinite
The frictional strength of brucite gouge has been measured at hydrothermal conditions to 450°C. At room temperature, brucite has a coefficient of friction, μ ≈ 0.30, making it one of the weakest minerals identified to date. With increasing temperature at a constant effective normal stress, the coefficient of friction of brucite decreases to a minimum of μ ≈ 0.20 near 300°C, and μ ≈ 0.22–0.24 in th
Authors
Diane E. Moore, David A. Lockner, K. Iwata, H. Tanaka, J. D. Byerlee
Energy-to-moment ratios for damaging intraslab earthquakes: preliminary results on a few case studies
We use the energy-to-moment ratio, as introduced by Newman and Okal [1998] to examine the source characteristics of normal-faulting intraslab earthquakes, compared to nearby interplate thrust events, based on recent case studies in central Chile and southeastern Mexico. In Chile, we find that the 1997 intraslab event had an exceptionally large E/M0 ratio, 30 times greater than the nearby interplat
Authors
Emile A. Okal, S. H. Kirby
Density and velocity relationships for digital sonic and density logs from coastal Washington and laboratory measurements of Olympic Peninsula mafic rocks and greywackes
Three-dimensional velocity models for the basins along the coast of Washington and in Puget Lowland provide a means for better understanding the lateral variations in strong ground motions recorded there. We have compiled 16 sonic and 18 density logs from 22 oil test wells to help us determine the geometry and physical properties of the Cenozoic basins along coastal Washington. The depth ranges sa
Authors
Thomas M. Brocher, Nikolas I. Christensen