Publications
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Airborne hunt for faults in the Portland-Vancouver area Airborne hunt for faults in the Portland-Vancouver area
Geologic hazards in the Portland-Vancouver area include faults entirely hidden by river sediments, vegetation, and urban development. A recent aerial geophysical survey revealed patterns in the Earth's magnetic field that confirm the existence of a previously suspected fault running through Portland. It also indicated that this fault may pose a significant seismic threat. This discovery...
Authors
Richard J. Blakely, Ray E. Wells, Thomas S. Yelin, Peter H. Stauffer, James W. Hendley
Comparison and contrast of processes of soil formation in the San Timoteo Badlands with chronosequences in California Comparison and contrast of processes of soil formation in the San Timoteo Badlands with chronosequences in California
The degree of soil development associated with geomorphic surfaces in the San Timoteo Badlands area (STB), California allows correlation of the surfaces. Soil development indices, based on field descriptions and laboratory analysis, provide a basis for comparison of these soils to each other and to dated soil chronosequences at Cajon Pass, Merced, and Anza, California. The soils in this...
Authors
Katherine J. Kendrick, Leslie D. McFadden
Earthquake-induced burial of archaeological sites along the southern Washington coast about A.D. 1700 Earthquake-induced burial of archaeological sites along the southern Washington coast about A.D. 1700
Although inhabited by thousands of people when first reached by Europeans, the Pacific coast of southern Washington has little recognized evidence of prehistoric human occupation. This apparent contradiction may be explained partly by geologic evidence for coastal submergence during prehistoric earthquakes on the Cascadia subduction zone. Recently discovered archaeological sites, exposed...
Authors
Steve C. Cole, Brian F. Atwater, Patrick T. McCutcheon, Julie K. Stein, Eileen Hemphill-Haley
Intermediate‐depth intraslab earthquakes and arc volcanism as physical expressions of crustal and uppermost mantle metamorphism in subducting slabs Intermediate‐depth intraslab earthquakes and arc volcanism as physical expressions of crustal and uppermost mantle metamorphism in subducting slabs
We elaborate on the well-known spatial association between axc volcanoes and Wadati Benioff zones and explore in detail their genetic relationships as dual physical expressions of slab metamorphism of the oceanic crust and uppermost mantle. At hypocentral depths less than 200 km intra slab Wadati-Benioff earthquakes tend to occur near the top surfaces of slabs. Subduction of very young...
Authors
Stephen H. Kirby, E. Robert Engdahl, Roger P. Denlinger
Earthquake technology fights crime Earthquake technology fights crime
Scientists with the U.S. Geological Survey have adapted their methods for quickly finding the exact source of an earthquake to the problem of locating gunshots. On the basis of this work, a private company is now testing an automated gunshot-locating system in a San Francisco Bay area community. This system allows police to rapidly pinpoint and respond to illegal gunfire, helping to...
Authors
John C. Lahr, Peter L. Ward, Peter H. Stauffer, James W. Hendley
Seismic anisotropy of the crystalline crust: What does it tell us? Seismic anisotropy of the crystalline crust: What does it tell us?
The study of the directional dependence of seismic velocities (seismic anisotropy) promises more refined insight into mineral composition and physical properties of the crystalline crust than conventional deep seismic refraction or reflection profiles providing average values of P-and S-wave velocities. The alignment of specific minerals by ductile rock deformation, for instance, causes...
Authors
Wolfgang Rabbel, Walter D. Mooney
Site-response maps for the Los Angeles region based on earthquake ground motions Site-response maps for the Los Angeles region based on earthquake ground motions
Ground-motion records from aftershocks of the 1994 Northridge earthquake and main-shock records from the 1971 San Fernando, 1987 Whittier Narrows, 1991 Sierra Madre, and 1994 Northridge earthquakes are used to estimate site response in the urban Los Angeles, California, area. Two frequency bands are considered, 0.5-1.5 Hz and 2.0-6.0 Hz. Instrument characteristics prevented going to...
Authors
Stephen H. Hartzell, Stephen C. Harmsen, Arthur D. Frankel, David L. Carver, Edward Cranswick, Mark E. Meremonte, John A. Michael
The Loma Prieta, California, Earthquake of October 17, 1989: Main shock characteristics The Loma Prieta, California, Earthquake of October 17, 1989: Main shock characteristics
The October 17, 1989, Loma Prieta, Calif., earthquake (0004:15.2 G.m.t. October 18; lat 37.036º N., long 121.883º W.; 19-km depth) had a local magnitude (ML) of about 6.7, a surface-wave magnitude (MS) of 7.1, a seismic moment of 2.2x1019 N-m to 3.5x1019 N-m, a source duration of 6 to 15 s, and an average stress drop of at least 50 bars. Slip occurred on a dipping fault surface about 35...
Authors
Paul A. Spudich, Gregory C. Beroza, George Choy, John Boatwright, Stephen H. Hartzell, Gordon L. Stewart, Carlos Mendoza, Stephen Horton, John G. Anderson, Andres J. Mendez, Hiroo Kanamori, Kenji Satake, Michael Lisowski, Mark Hunter Murray, Jerry L. Svarc, Grant Marshall, Ross S. Stein, Karen McNally, Gerald W. Simila, Judy G. Brown, J.L. Nabelek, Ze’ev Reches, Mark D. Zoback, Jamison Steidl, Ralph J. Archuleta, Aaron A. Velasco, Thorne Lay, Jiajun Zhang, David J. Wald, Donald V. Helmberger, Thomas H. Heaton, Chesley R. Williams, Paul Segall, Francis T. Wu, Mingdong Wu, J.W. Rudnicki
Damage and restoration of geodetic infrastructure caused by the 1994 Northridge, California, earthquake Damage and restoration of geodetic infrastructure caused by the 1994 Northridge, California, earthquake
We seek to restore the integrity of the geodetic network in the San Fernando, Simi, Santa Clarita Valleys and in the northern Los Angeles Basin by remeasurement of the network and identification of BMs which experienced non-tectonic displacements associated with the Northridge earthquake. We then use the observed displacement of BMs in the network to portray or predict the permanent...
Authors
Kathleen M. Hodgkinson, Ross S. Stein, Kenneth W. Hudnut, Jay Satalich, John H. Richards
Quake Forecasting- An Emerging Capability Quake Forecasting- An Emerging Capability
No abstract available.
Authors
Andrew Michael, Paul Reasenberg, Peter H. Stauffer, James W. Hendley
Origin of high mountains in the continents: The Southern Sierra Nevada Origin of high mountains in the continents: The Southern Sierra Nevada
Active and passive seismic experiments show that the southern Sierra, despite standing 1.8 to 2.8 kilometers above its surroundings, is underlain by crust of similar seismic thickness, about 30 to 40 kilometers. Thermobarometry of xenolith suites and magnetotelluric profiles indicate that the upper mantle is eclogitic to depths of 60 kilometers beneath the western and central parts of...
Authors
B. Wernicke, R. Clayton, Mihai N. Ducea, C.H. Jones, S. Park, S. Ruppert, J. Saleeby, J.K. Snow, L. Squires, M. Fliedner, G. Jiracek, Rebecca Hylton Keller, S. Klemperer, J. Luetgert, P. Malin, K. Miller, Walter D. Mooney, H. Oliver, R. Phinney
Transition from slab to slabless: Results from the 1993 Mendocino triple junction seismic experiment Transition from slab to slabless: Results from the 1993 Mendocino triple junction seismic experiment
Three seismic refraction-reflection profiles, part of the Mendocino triple junction seismic experiment, allow us to compare and contrast crust and upper mantle of the North American margin before and after it is modified by passage of the Mendocino triple junction. Upper crustal velocity models reveal an asymmetric Great Valley basin overlying Sierran or ophiolitic rocks at the latitude...
Authors
B. C. Beaudoin, N. J. Godfrey, S.L. Klemperer, C. Lendl, A.M. Trehu, T.J. Henstock, A. Levander, J.E. Holl, A.S. Meltzer, James H. Luetgert, Walter D. Mooney