Publications
Filter Total Items: 7621
Seismic structure of the uppermost mantle beneath the Kenya rift Seismic structure of the uppermost mantle beneath the Kenya rift
A major goal of the Kenya Rift International Seismic Project (KRISP) 1990 experiment was the determination of deep lithospheric structure. In the refraction/wide-angle reflection part of the KRISP effort, the experiment was designed to obtain arrivals to distances in excess of 400 km. Phases from interfaces within the mantle were recorded from many shotpoints, and by design, the best...
Authors
Gordon R. Keller, J. Mechie, L.W. Braile, Walter D. Mooney, C. Prodehl
Magmatic vapor source for sulfur dioxide released during volcanic eruptions: Evidence from Mount Pinatubo Magmatic vapor source for sulfur dioxide released during volcanic eruptions: Evidence from Mount Pinatubo
Sulfur dioxide (SO2) released by the explosive eruption of Mount Pinatubo on 15 June 1991 had an impact on climate and stratospheric ozone. The total mass of SO2 released was much greater than the amount dissolved in the magma before the eruption, and thus an additional source for the excess SO2 is required. Infrared spectroscopic analyses of dissolved water and carbon dioxide in glass...
Authors
P.J. Wallace, T.M. Gerlach
The KRISP 90 seismic experiment-a technical review The KRISP 90 seismic experiment-a technical review
On the basis of a preliminary experiment in 1985 (KRISP 85), a seismic refraction/wide-angle reflection survey and a teleseismic tomography experiment were jointly undertaken to study the lithospheric structure of the Kenya rift down to depths of greater than 200 km. This report serves as an introduction to a series of subsequent papers and will focus on the technical description of the...
Authors
C. Prodehl, J. Mechie, U. Achauer, Gordon R. Keller, M.A. Khan, Walter D. Mooney, S.J. Gaciri, J.D. Obel
Precursory swarms of long-period events at Redoubt Volcano (1989-1990), Alaska: Their origin and use as a forecasting tool Precursory swarms of long-period events at Redoubt Volcano (1989-1990), Alaska: Their origin and use as a forecasting tool
During the eruption of Redoubt Volcano from December 1989 through April 1990, the Alaska Volcano Observatory issued advance warnings of several tephra eruptions based on changes in seismic activity related to the occurrence of precursory swarms of long-period (LP) seismic events (dominant period of about 0.5 s). The initial eruption on December 14 occurred after 23 years of quiescence...
Authors
B. A. Chouet, R.A. Page, C.D. Stephens, J.C. Lahr, J.A. Power
Increased pressure from rising bubbles as a mechanism for remotely triggered seismicity Increased pressure from rising bubbles as a mechanism for remotely triggered seismicity
Aftershocks of large earthquakes tend to occur close to the main rupture zone, and can be used to constrain its dimensions. But following the 1992 Landers earthquake (magnitude M(w) = 7.3) in southern California, many aftershocks were reported in areas remote from the mainshock. Intriguingly, this remote seismicity occurred in small clusters near active volcanic and geothermal systems...
Authors
A. T. Linde, I. S. Sacks, M.J.S. Johnston, D.P. Hill, R.G. Bilham
The East African rift system in the light of KRISP 90 The East African rift system in the light of KRISP 90
On the basis of a test experiment in 1985 (KRISP 85) an integrated seismic-refraction/teleseismic survey (KRISP 90) was undertaken to study the deep structure beneath the Kenya rift down to depths of 100–150 km. This paper summarizes the highlights of KRISP 90 as reported in this volume and discusses their broad implications as well as the structure of the Kenya rift in the general...
Authors
Gordon R. Keller, C. Prodehl, J. Mechie, K. Fuchs, M.A. Khan, Peter K.H. Maguire, Walter D. Mooney, U. Achauer, P.M. Davis, R.P. Meyer, L.W. Braile, I.O. Nyambok, G. A. Thompson
Rare earth element contents and multiple mantle sources of the transform-related Mount Edgecumbe basalts, southeastern Alaska Rare earth element contents and multiple mantle sources of the transform-related Mount Edgecumbe basalts, southeastern Alaska
Pleistocene basalt of the Mount Edgecumbe volcanic field (MEF) is subdivided into a plagioclase type and an olivine type. Olivine basalt crops out farther inboard from the nearby Fairweather transform than plagioclase basalt. Th/La ratios of plagioclase basalt are similar to those of mid-ocean-ridge basalt (MORB), whereas those of olivine basalt are of continental affinity. The olivine...
Authors
J.R. Riehle, J. R. Budahn, M. A. Lanphere, D. A. Brew
Potential for seepage erosion of landslide dam Potential for seepage erosion of landslide dam
The failure potential of the debris-avalanche dam at Castle Lake near Mount St. Helens, Washington, by three processes of seepage erosion (1) Heave; (2) piping; and (3) internal erosion, is examined. Results indicated that the dam is stable against piping but potentially locally unstable against heave. -from Authors
Authors
W. Meyer, R. L. Schuster, M. A. Sabol
Eruptive activity at Mount St Helens, Washington, USA, 1984-1988: a gas geochemistry perspective Eruptive activity at Mount St Helens, Washington, USA, 1984-1988: a gas geochemistry perspective
The results from two different types of gas measurement, telemetered in situ monitoring of reducing gases on the dome and airborne measurements of sulfur dioxide emission rates in the plume by correlation spectrometry, suggest that the combination of these two methods is particularly effective in detecting periods of enhanced degassing that intermittently punctuate the normal background...
Authors
K.A. McGee, A. J. Sutton
Potassium-argon geochronology of a basalt-andesite-dacite arc system: the Mount Adams volcanic field, Cascade Range of southern Washington Potassium-argon geochronology of a basalt-andesite-dacite arc system: the Mount Adams volcanic field, Cascade Range of southern Washington
High-precision K-Ar dating and detailed mapping have established an eruptive chronology for a Cascade stratovolcano and its surrounding array of coeval basaltic centers. The time-volume-composition data bear upon several fundamental questions concerning the long-term behavior of arc volcanoes. -from Authors
Authors
W. Hildreth, M. A. Lanphere
Six years of change in Lake Nyos, Cameroon, yield clues to the past and cautions for the future Six years of change in Lake Nyos, Cameroon, yield clues to the past and cautions for the future
The catastrophic release of gas from Lake Nyos, Cameroon, in 1986 caused substantial but incomplete mixing of the stratified water column. The post-release evolution of water-column structure has been monitored through April 1992. Changes began immediately after the event as rainfall and inflow brought dilute fluid into the surface layer. Inflow and surface mixing have gradually deepened...
Authors
William C. Evans, L. D. White, M. L. Tuttle, G.W. Kling, G. Tanyileke, R. L. Michel
Volcanic mixed avalanches: A distinct eruption-triggered mass-flow process at snow-clad volcanoes Volcanic mixed avalanches: A distinct eruption-triggered mass-flow process at snow-clad volcanoes
A generally unrecognized type of pyroclastic deposit was produced by rapid avalanches of intimately mixed snow and hot pyroclastic debris during eruptions at Mount St. Helens, Nevado del Ruiz, and Redoubt Volcano between 1982 and 1989. These "mixed avalanches" traveled as far as 14 km at velocities up to ∼27 m/s, involved as much as 107 m3 of rock and ice, and left unmelted deposits of...
Authors
T.C. Pierson, R. J. Janda