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Tectonics and seismicity of the southern Washington Cascade range Tectonics and seismicity of the southern Washington Cascade range

Geophysical, geological, and seismicity data are combined to develop a transpressional strain model for the southern Washington Cascades region. We use this model to explain oblique fold and fault systems, transverse faults, and a linear seismic zone just west of Mt. Rainier known as the western Rainier zone. We also attempt to explain a concentration of earthquakes that connects the...
Authors
W. D. Stanley, S. Y. Johnson, A.I. Qamar, C.S. Weaver, J. M. Williams

Landslides triggered by the 1994 Northridge, California, earthquake Landslides triggered by the 1994 Northridge, California, earthquake

The 17 January 1994 Northridge, California, earthquake (Mw = 6.7) triggered more than 11,000 landslides over an area of about 10,000 km2. Most of the landslides were concentrated in a 1000-km2 area that included the Santa Susana Mountains and the mountains north of the Santa Clara River valley. We mapped landslides triggered by the earthquake in the field and from 1:60,000-nominal-scale...
Authors
E. L. Harp, R.W. Jibson

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

Recurrent eruption and subsidence at the Platoro caldera complex, southeastern San Juan volcanic field, Colorado: New tales from old tuffs Recurrent eruption and subsidence at the Platoro caldera complex, southeastern San Juan volcanic field, Colorado: New tales from old tuffs

Reinterpretation of a voluminous regional ash-flow sheet (Masonic Park Tuff) as two separate tuff sheets of similar phenocryst-rich dacite erupted from separate source calderas has important implications for evolution of the multicyclic Platoro caldera complex and for caldera-forming processes generally. Masonic Park Tuff in central parts of the San Juan field, including the type area...
Authors
P. W. Lipman, M.A. Dungan, L.L. Brown, A. Deino

Outburst floods from glacier-dammed lakes: The effect of mode of lake drainage on flood magnitude Outburst floods from glacier-dammed lakes: The effect of mode of lake drainage on flood magnitude

Published accounts of outburst floods from glacier‐dammed lakes show that a significant number of such floods are associated not with drainage through a tunnel incised into the basal ice—the process generally assumed—but rather with ice‐marginal drainage, mechanical failure of part of the ice dam, or both. Non‐tunnel floods are strongly correlated with formation of an ice dam by a...
Authors
Joseph S. Walder, John E. Costa

Volatile emissions from the crater and flank of Oldoinyo Lengai volcano, Tanzania Volatile emissions from the crater and flank of Oldoinyo Lengai volcano, Tanzania

As a comparison to airborne infrared (IR) flux measurements, ground-based sampling of fumarole and soil gases was used to characterize the quiescent degassing of CO2 from Oldoinyo Lengai volcano. Aerial and ground-based measurements are in good agreement: ∼75% of the aerially measured CO2 flux at Lengai (0.05–0.06 × 1012 mol yr−1 or 6000–7200 tonnes CO2 d−1) can be attributed to seven...
Authors
K.W. Koepenick, S.L. Brantley, J. M. Thompson, G.L. Rowe, A.A. Nyblade, C. Moshy

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

Aeromagnetic survey over US to advance geomagnetic research Aeromagnetic survey over US to advance geomagnetic research

A proposed high-altitude survey of the United States offers an exciting and cost effective opportunity to collect magnetic-anomaly data. Lockheed Martin Missile and Space Company is considering funding a reimbursable ER-2 aircraft (Figure 1) mission to collect synthetic aperture radar (SAR) imagery at an altitude of about 21 km over the conterminous United States and Alaska. The...
Authors
T.G. Hildenbrand, R.J. Blakely, W. J. Hinze, Gordon R. Keller, R.A. Langel, M. Nabighian, W. Roest

The Springdale, Utah, landslide: An extraordinary event The Springdale, Utah, landslide: An extraordinary event

The most dramatic geologic effect of the M-5.7 St. George, Utah earthquake of 2 September 1992 was the triggering of the 14,000,000-m3 Springdale, Utah landslide. The roughly 10 m of landslide movement destroyed three houses, threatened several condominiums, disrupted utility lines, and temporarily closed the southwest entrance to Zion National Park. The seismic triggering of this...
Authors
R.W. Jibson, E. L. Harp
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