Publications
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Catalog of earthquake hypocenters for Augustine, Redoubt, Iliamna, and Mount Spurr volcanoes, Alaska: January 1, 1991 - December 31, 1993 Catalog of earthquake hypocenters for Augustine, Redoubt, Iliamna, and Mount Spurr volcanoes, Alaska: January 1, 1991 - December 31, 1993
The Alaska Volcano Observatory (AVO), a cooperative program of the U.S. Geological Survey, the Geophysical Institute of the University of Alaska, Fairbanks, and the Alaska Division of Geological and Geophysical Surveys, has maintained a program of seismic monitoring at potentially active volcanoes in the Cook Inlet region since 1988. The principal objectives of this program include the...
Authors
Arthur D. Jolly, John A. Power, Scott D. Stihler, Lalitha N. Rao, Gail Davidson, John F. Paskievitch, Steve Estes, John C. Lahr
Three-dimensional seismic image of a geothermal reservoir: The Geysers, California Three-dimensional seismic image of a geothermal reservoir: The Geysers, California
Three-dimensional seismic travel-time tomography of The Geysers geothermal area, in the coast ranges of northern California, shows a strong (−9%) anomaly in VP/VS, the ratio of the compressional and shear wave speeds, that is not evident in VP alone and corresponds closely to the most intensively exploited part of the geothermal reservoir. This anomaly probably indicates low pore...
Authors
B.R. Julian, A. Ross, G.R. Foulger, J.R. Evans
Exsolved magmatic fluid and its role in the formation of comb-layered quartz at the Cretaceous Logtung W-Mo deposit, Yukon Territory, Canada Exsolved magmatic fluid and its role in the formation of comb-layered quartz at the Cretaceous Logtung W-Mo deposit, Yukon Territory, Canada
Comb-layered quartz is a type of unidirectional solidification texture found at the roofs of shallow silicic intrusions that are often associated spatially with Mo and W mineralisation. The texture consists of multiple layers of euhedral, prismatic quartz crystals (Type I) that have grown on subplanar aplite substrates. The layers are separated by porphyritic aplite containing equant...
Authors
J. B. Lowenstern, W.D. Sinclair
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
Aeromagnetic map of the Clear Lake region on parts of the Santa Rosa and Ukih 1° by 2° quadrangles, California Aeromagnetic map of the Clear Lake region on parts of the Santa Rosa and Ukih 1° by 2° quadrangles, California
No abstract available.
Authors
Water Resources Division U.S. Geological Survey
The initial cooling of pahoehoe flow lobes The initial cooling of pahoehoe flow lobes
In this paper we describe a new thermal model for the initial cooling of pahoehoe lava flows. The accurate modeling of this initial cooling is important for understanding the formation of the distinctive surface textures on pahoehoe lava flows as well as being the first step in modeling such key pahoehoe emplacement processes as lava flow inflation and lava tube formation. This model is
Authors
L. Keszthelyi, R. Denlinger
Channel adjustment of an unstable coarse-grained stream: Opposing trends of boundary and critical shear stress, and the applicability of extremal hypotheses Channel adjustment of an unstable coarse-grained stream: Opposing trends of boundary and critical shear stress, and the applicability of extremal hypotheses
Channel adjustments in the North Fork Toutle River and the Toutle River main stem were initiated by deposition of a 2.5km3 debris avalanche and associated lahars that accompanied the catastrophic eruption of Mount St. Helens, Washington on 18 May 1980. Channel widening was the dominant process. In combination, adjustments caused average boundary shear stress to decrease non-linearly with...
Authors
Andrew Simon, Colin R. Thorne
Growth of the Tongariro volcanic complex: New evidence from K-Ar age determinations Growth of the Tongariro volcanic complex: New evidence from K-Ar age determinations
New K-Ar age determinations indicate that the exposed portion of the Tongariro volcanic complex has grown steadily since at least 275 ka, with intervals of vigorous cone growth at 210-200.130-70. and 25 ka to the present day.
Authors
B.J. Hobden, Bruce F. Houghton, M. A. Lanphere, I.A. Nairn
Volcanic activity in Alaska and Kamchatka: Summary of events and response of the Alaska Volcano Observatory 1995 Volcanic activity in Alaska and Kamchatka: Summary of events and response of the Alaska Volcano Observatory 1995
The Alaska Volcano Observatory (AVO) responded to eruptive activity or suspected volcanic activity (SVA) at 6 volcanic centers in 1995: Mount Martin (Katmai Group), Mount Veniaminof, Shishaldin, Makushin, Kliuchef/Korovin, and Kanaga. In addition to responding to eruptive activity at Alaska volcanoes, AVO also disseminated information for the Kamchatkan Volcanic Eruption Response Team...
Authors
Robert G. McGimsey, Christina A. Neal
Provisional geologic map of Augustine Volcano, Alaska Provisional geologic map of Augustine Volcano, Alaska
No abstract available.
Authors
R. B. Waitt, J. E. Beget, Juergen Kienle
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
A new model for the emplacement of Columbia River basalts as large, inflated pahoehoe lava flow fields A new model for the emplacement of Columbia River basalts as large, inflated pahoehoe lava flow fields
Extensive flows of the Columbia River Basalt (CRB) Group in Washington, Oregon, and Idaho are dominantly inflated compound pahoehoe sheet lavas. Early studies recognized that CRB lavas are compound pahoehoe flows, with textures suggesting low flow velocities, but it was thought that the great thickness and extent of the major flows required very rapid emplacement as turbulent floods of...
Authors
S. Self, Th. Thordarson, L. Keszthelyi, G.P.L. Walker, K. Hon, M.T. Murphy, P. Long, S. Finnemore