A5052579048- Seismic Waves and Analysis
- earthquake and tectonic studies
- Seismic Imaging and Inversion Techniques
- Geological and Geochemical Analysis
- Seismology and Earthquake Studies
- High-pressure geophysics and materials
- Seismic Performance and Analysis
- Underwater Acoustics Research
- Geological Modeling and Analysis
- Geology and Paleoclimatology Research
- Earthquake Detection and Analysis
- Geological Studies and Exploration
- Geological formations and processes
- Geological and Geophysical Studies
- Drilling and Well Engineering
- Landslides and related hazards
- Methane Hydrates and Related Phenomena
- Geochemistry and Geologic Mapping
- Geophysical and Geoelectrical Methods
- Hydrocarbon exploration and reservoir analysis
- Geophysics and Sensor Technology
- Reservoir Engineering and Simulation Methods
- Astro and Planetary Science
- Structural Response to Dynamic Loads
- Island Studies and Pacific Affairs
United States Geological Survey
2005-2018
Entertainment Industries Council
2017
Grays Harbor College
2017
Earth and Space Research
2003
University of Washington
2000-2003
Oregon State University
2000-2003
University of Nevada, Las Vegas
2002
The University of Texas at El Paso
2000-2002
Denver Federal Center
2002
Pacific Island Ecosystems Research Center
2000
A compilation of compressional-wave ( V p) and shear-wave s) velocities densities for a wide variety common lithologies is used to define new nonlinear, multivalued, quantitative relations between these properties the Earth's crust. Wireline borehole logs, vertical seismic profiles, laboratory measurements, tomography models provide diverse dataset deriving empirical crustal p s. The proposed s as function fit logs in Quaternary alluvium Salinian granites well measurements over 7-km/sec-wide...
We analyze four expanded spread profiles acquired at distances of 0, 2.1, 3.1, and 10 km (0–0.2 m.y.) from the axis East Pacific Rise between 9° 10°N. Velocity‐depth models for these have been obtained by travel time inversion in τ‐ p domain, x ‐ t forward modeling using WKBJ reflectivity methods. observe refracted arrivals that allow us to determine directly uppermost crustal velocity structure (layer 2A). At seafloor we find very low V S / values around 2.2 km/s ≤ 0.43. In topmost 100–200...
We present the results of analysis expanding spread profiles (ESPs) collected on and near axis East Pacific Rise at 13°N. These were 0, 1.1, 2.1, 3.6, 9.5 km from rise axis, all but most distant profile show a distinct low‐velocity zone (LVZ) located within layer 3 oceanic crust. At ridge crest, top magma chamber is base 2, while 3.6 off roof LVZ 1.1 below 3. The farthest could possibly have residual confined to lower 1.5 total width LVZ, as determined ESP data, least 6 km, much greater....
In southern and central Alaska the subduction active volcanism of Aleutian zone give way to a broad plate boundary with mountain building strike‐slip faulting, where Yakutat terrane joins subducting Pacific plate. The interplay these tectonic elements can be best understood by considering entire region in three dimensions. We image three‐dimensional seismic velocity using abundant local earthquakes, supplemented source data. Crustal low‐velocity correlates basins. Denali fault is dominant...
Seismic profiling data indicate that the thickness of an accreted oceanic terrane Paleocene and early Eocene age, which forms basement much forearc beneath western Oregon Washington, varies by approximately a factor 4 along strike Cascadia subduction zone. Beneath Coast Range, is 25 to 35 kilometers thick, whereas offshore Vancouver Island it about 6 thick. These variations are correlated with in arc magmatism, seismicity, long-term deformation. It suggested strength crust increases as...
Research Article| June 01, 2005 Subduction-zone magnetic anomalies and implications for hydrated forearc mantle Richard J. Blakely; Blakely 1U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025, USA Search other works by this author on: GSW Google Scholar Thomas M. Brocher; Brocher Ray E. Wells Author Article Information Publisher: Society of America Received: 07 Dec 2004 Revision 22 Feb Accepted: 01 Mar First Online: 03 2017 Online ISSN: 1943-2682 Print 0091-7613 The...
Coincident multichannel seismic reflection and refraction data acquired during a wide‐aperture two‐ship experiment provide evidence for complex crust‐mantle (C‐M) transition under Oahu, Hawaii. Several large‐aperture common depth point lines three expanding spread profiles suggest the existence of an anomalously thick (3–6 km) C‐M zone underneath volcanic ridge which extends distances 100 km to north south from center Oahu. The anomalous may represent plutonic intruded into upper mantle...
Research Article| March 01, 2003 Seismic evidence for widespread serpentinized forearc upper mantle along the Cascadia margin Thomas M. Brocher; Brocher 1U.S. Geological Survey, MS 977, Menlo Park, California 94025, USA Search other works by this author on: GSW Google Scholar Tom Parsons; Parsons 2U.S. 999, Anne Tréhu; Tréhu 3College of Oceanography, Oceanography Administration Building 104, Oregon State University, Corvallis, 97331, Catherine Snelson; Snelson 4Department Geoscience,...
In the northern Gulf of Alaska and Prince William Sound, we have used wide‐angle seismic reflection/refraction profiles, earthquake studies, laboratory measurements physical properties to determine geometry Yakutat terranes, Aleutian megathrust, subducting Pacific plate. this complex region, terrane is underthrust beneath terrane, both terranes are interpreted be underlain by Wide‐angle profiles recorded along five lines unravel geometry. Modeled velocities in upper crust (to 18 km depth)...
Research Article| May 01, 1991 EDGE deep seismic reflection transect of the eastern Aleutian arc-trench layered lower crust reveals underplating and continental growth J. Casey Moore; Moore 1Department Earth Sciences, University California, Santa Cruz, California 95064 Search for other works by this author on: GSW Google Scholar John Diebold; Diebold 2Lamont Doherty Geological Observatory, Columbia University, Palisades, New York 10964 M. A. Fisher; Fisher 3U.S. Survey, 345 Middlefield Road,...
Abstract This article presents new empirical compressional and shear-wave velocity ( Vp Vs ) versus depth relationships for the most common rock types in northern California. relations were developed from borehole, laboratory, seismic refraction tomography, density measurements, converted to using between . The proposed here account increasing overburden pressure but not variations other factors that can influence over short distance scales, such as lithology, consolidation, induration,...
Abstract We simulate long-period ( T >1.0–2.0 s) and broadband >0.1 ground motions for 39 scenario earthquakes M w 6.7–7.2) involving the Hayward, Calaveras, Rodgers Creek faults. For rupture on Hayward fault, we consider effects of creep coseismic slip using two different approaches, both which reduce motions, compared with neglecting influence creep. Nevertheless, generate strong shaking throughout San Francisco Bay area, about 50% urban area experiencing modified Mercalli intensity VII...
The M w 6.0 South Napa earthquake, which occurred at 10:20 UTC 24 August 2014 was the largest earthquake to strike greater San Francisco Bay area since w 6.9 1989 Loma Prieta earthquake. rupture from this right‐lateral propagated mostly unilaterally north and up‐dip, directing strongest shaking toward city of Napa, where peak ground accelerations (PGAs) between 45% g 61% were recorded modified Mercalli intensities (MMIs) VII–VIII reported. Tectonic surface with dextral slip up 46 cm observed...
A new three‐dimensional (3‐D) model shows seismic velocities beneath the Puget Lowland to a depth of 11 km. The is based on tomographic inversion nearly one million first‐arrival travel times recorded during 1998 Seismic Hazards Investigation in Sound (SHIPS), allowing higher‐resolution mapping subsurface structures than previously possible. allows us refine geometry proposed faults (e.g., Seattle, Hood Canal, southern Whidbey Island, and Devils Mountain fault zones) as well identify...
Research Article| August 01, 1990 Seismic anisotropy due to preferred mineral orientation observed in shallow crustal rocks southern Alaska Thomas M. Brocher; Brocher 1U.S. Geological Survey, M.S. 977, 345 Middlefield Road, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar Nikolas I. Christensen 2Department of Earth & Atmospheric Sciences, Purdue University, West Lafayette, Indiana 47907 Author and Article Information Publisher: Society America First...
We simultaneously invert travel times of refracted and wide-angle reflected waves for three-dimensional compressional-wave velocity structure, earthquake locations, reflector geometry in northwest Washington state. The reflector, interpreted to be the crust-mantle boundary (Moho) subducting Juan de Fuca plate, separates intraslab earthquakes into two groups, permitting a new understanding origins Cascadia. Earthquakes up-dip Moho's 45-kilometer depth contour occur below subducted oceanic...
Research Article| April 01, 2008 Ground-Motion Modeling of the 1906 San Francisco Earthquake, Part II: Estimates for Earthquake and Scenario Events Brad T. Aagaard; Aagaard U.S. Geological Survey, MS977, 345 Middlefield Rd., Menlo Park, California 94025 Search other works by this author on: GSW Google Scholar Thomas M. Brocher; Brocher David Dolenc; Dolenc Seismological Laboratory, University California, Berkeley, 215 McCone Hall, 94720 Douglas Dreger; Dreger Robert W. Graves; Graves URS...
We obtain a seismic velocity model of the California crust and uppermost mantle using regional-scale double-difference tomography algorithm.We begin by absolute arrival-time picks to solve for coarse three-dimensional (3D) P (V ) with uniform 30 km horizontal node spacing, which we then use as starting finer-scale inversion applied differential pick times.For computational reasons, split state into 5 subregions grid spacing 10 20 assemble our final statewide V stitching together these local...
We compute ground motions for the Beroza (1991) and Wald et al. source models of 1989 magnitude 6.9 Loma Prieta earthquake using four different wave-propagation codes recently developed 3D geologic seismic velocity models. In preparation modeling 1906 San Francisco earthquake, we use this well-recorded to characterize how well our ground-motion simulations reproduce observed shaking intensities amplitude durations recorded throughout Bay Area. All generate consistent with large-scale spatial...
Research Article| January 01, 2004 Holocene fault scarps near Tacoma, Washington, USA Brian L. Sherrod; Sherrod 1U.S. Geological Survey, Department of Earth and Space Sciences, University Box 351310, Seattle, Washington 98195, Search for other works by this author on: GSW Google Scholar Thomas M. Brocher; Brocher 2U.S. MS 977, 345 Middlefield Road, Menlo Park, California 94025, Craig S. Weaver; Weaver 3U.S. Robert C. Bucknam; Bucknam 4U.S. 966, Denver Federal Center, Lakewood, Colorado...
This paper presents the first regional three‐dimensional P wave velocity model for Northern Cascadia Subduction Zone (SW British Columbia and NW Washington State) constructed through tomographic inversion of first‐arrival traveltime data from active source experiments together with earthquake recorded at permanent stations. The images structure subducting Juan de Fuca plate, megathrust, fore‐arc crust upper mantle. Beneath southern Vancouver Island megathrust above plate is characterized by...