Publications
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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
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
Rockslide-debris avalanche of May 18, 1980, Mount St. Helens Volcano, Washington Rockslide-debris avalanche of May 18, 1980, Mount St. Helens Volcano, Washington
This report provides a detailed picture of the rockslide-debris avalanche of the May 18, 1980, eruption of Mount St. Helens volcano. It provides a characterization of the deposit, a reinterpretation of the details of the first minutes of the eruption of May 18, and insight into the transport mechanism of the mass movement. Details of the rockslide event, as revealed by eyewitness...
Authors
Harry Glicken
Hot dry rock and the U.S. geological survey: a question of priorities Hot dry rock and the U.S. geological survey: a question of priorities
The enactment of the Energy Policy Act of 1992 saw the assignment of definite responsibilities relating to hot dry rock (HDR) to the US Geological Survey (USGS). This mandate provided some explicit guidelines and individual tasks in areas in which the USGS already had close ties to the Department of Energy and a number of its national laboratories. This paper discusses various tasks in...
Authors
John H. Sass
Geomagnetic storms, the Dst ring-current myth and lognormal distributions Geomagnetic storms, the Dst ring-current myth and lognormal distributions
The definition of geomagnetic storms dates back to the turn of the century when researchers recognized the unique shape of the H-component field change upon averaging storms recorded at low latitude observatories. A generally accepted modeling of the storm field sources as a magnetospheric ring current was settled about 30 years ago at the start of space exploration and the discovery of...
Authors
W.H. Campbell
Geology of 243 Ida Geology of 243 Ida
The surface of 243 Ida is dominated by the effects of impacts. No complex crater morphologies are observed. A complete range of crater degradation states is present, which also reveals optical maturation of the surface (darkening and reddening of materials with increasing exposure age). Regions of bright material associated with the freshest craters might be ballistically emplaced...
Authors
R. Sullivan, R. Greeley, R. Pappalardo, E. Asphaug, Johnnie N. Moore, D. Morrison, M. J. S. Belton, M. Carr, C. R. Chapman, Paul E. Geissler, R. Greenberg, J. Granahan, J. W. Head, Randolph L. Kirk, A. McEwen, P. Lee, P.C. Thomas, J. Veverka
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
Mount St. Augustine volcano fumarole wall rock alteration: Mineralogy, zoning, composition and numerical models of its formation process Mount St. Augustine volcano fumarole wall rock alteration: Mineralogy, zoning, composition and numerical models of its formation process
Intensely altered wall rock was collected from high-temperature (640 °C) and low-temperature (375 °C) vents at Augustine volcano in July 1989. The high-temperature altered rock exhibits distinct mineral zoning differentiated by color bands. In order of decreasing temperature, the color bands and their mineral assemblages are: (a) white to grey (tridymite-anhydrite); (b) pink to red...
Authors
A. Getahun, M.H. Reed, R. Symonds
Thermal conductivity of water-saturated rocks from the KTB pilot hole at temperatures of 25 to 300°C Thermal conductivity of water-saturated rocks from the KTB pilot hole at temperatures of 25 to 300°C
The conductivitites of selected gneiss (two) and amphibolite (one) core samples have been measured under conditions of elevated temperature and pressure with a needle‐probe. Water‐saturated thermal conductivity measurements spanning temperatures from 25 to 300°C and hydrostatic pressures of 0.1 and 34 MPa confirm the general decrease in conductivity with increasing temperature but...
Authors
D. Pribnow, C.F. Williams, J.H. Sass, R. Keating
Geyser periodicity and the response of geysers to deformation Geyser periodicity and the response of geysers to deformation
Numerical simulations of multiphase fluid and heat transport through a porous medium define combinations of rock properties and boundary conditions which lead to geyser‐like periodic discharge. Within the rather narrow range of conditions that allow geyser‐like behavior, eruption frequency and discharge are highly sensitive to the intrinsic permeabilities of the geyser conduit and the...
Authors
S. E. Ingebritsen, S.A. Rojstaczer
Non-double-couple earthquake mechanisms at the Geysers geothermal area, California Non-double-couple earthquake mechanisms at the Geysers geothermal area, California
Inverting P- and S-wave polarities and P:SH amplitude ratios using linear programming methods suggests that about 20% of earthquakes at The Geysers geothermal area have significantly non-double-couple focal mechanisms, with explosive volumetric components as large as 33% of the seismic moment. This conclusion contrasts with those of earlier studies, which interpreted data in terms of...
Authors
A. Ross, G.R. Foulger, B.R. Julian
Origin and depositional environment of clastic deposits in the Hilo drill hole, Hawaii Origin and depositional environment of clastic deposits in the Hilo drill hole, Hawaii
Volcaniclastic units cored at depths of about 87, 164, 178, 226, and 246 m below sea level and carbonate units located between depths of 27 and 53 m below sea level in the Hilo drill core were found to be deposited at or near sea level. Four of these units are hydroclastic deposits, formed when subaerially erupted Mauna Loa lava flows entered the ocean and fragmented to produce quenched...
Authors
M.H. Beeson, D.A. Clague, J. P. Lockwood