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Science 4 May 1979:
Vol. 204. no. 4392, pp. 495 - 497
DOI: 10.1126/science.204.4392.495
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Articles

Abnormal P-Wave Delays in The Geysers—Clear Lake Geothermal Area, California

H. M. IYER 1, D. H. OPPENHEIMER 1, and T. HITCHCOCK 1

1 Office of Earthquake Studies, U.S. Geological Survey, Menlo Park, California 94025

Large teleseismic delays, exceeding 1 second, are found near Mount Hannah in the Clear Lake volcanic field and in the steam-production area at The Geysers. The delays are superimposed on a general delay field of about 0.5 second extending over the volcanic rocks and the steam reservoir. It is postulated that a magma chamber under the surface volcanic rocks with a core of severely molten rock beneath Mount Hannah and a highly fractured steam reservoir probably underlain by partially molten rock at The Geysers are responsible for the observed delays. Both zones extend to depths of 20 kilometers or more.

Submitted on October 23, 1978
Revised on February 22, 1979


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
A dipping Moho and crustal low-velocity zone from Pn arrivals at The Geysers-Clear Lake, California.
P. M. SHEARER and D. H. OPPENHEIMER (1982)
Bulletin of the Seismological Society of America 72, 1551-1566
   Abstract »    PDF »
Comparison of seismicity in the Geysers geothermal area with the surrounding region.
R. S. LUDWIN, V. CAGNETTI, and C. G. BUFE (1982)
Bulletin of the Seismological Society of America 72, 863-871
   Abstract »    PDF »
Sierra Nevada-Great Basin boundary zone: Earthquake hazard related to structure, active tectonic processes, and anomalous patterns of earthquake occurrence.
J. D. VANWORMER and A. S. RYALL (1980)
Bulletin of the Seismological Society of America 70, 1557-1572
   Abstract »    PDF »


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