Title: Seismicity of a caldera collapse: Galapagos Islands 1968
Abstract: Journal of Geophysical Research (1896-1977)Volume 78, Issue 35 p. 8591-8622 Seismicity of a caldera collapse: Galapagos Islands 1968 John Filson, John FilsonSearch for more papers by this authorTom Simkin, Tom SimkinSearch for more papers by this authorLei-kuang Leu, Lei-kuang LeuSearch for more papers by this author John Filson, John FilsonSearch for more papers by this authorTom Simkin, Tom SimkinSearch for more papers by this authorLei-kuang Leu, Lei-kuang LeuSearch for more papers by this author First published: 10 December 1973 https://doi.org/10.1029/JB078i035p08591Citations: 114AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Abstract The seismicity associated with the collapse of a volcanic caldera in the Galapagos Islands during June of 1968 has been studied in detail. The rate of seismic energy release, inferred from some 638 assigned surface wave magnitudes, was constant over a 9-day period and appears to be consistent with removal of magmatic support at a constant rate. Early in the earthquake sequence, the energy release was periodic. Large earthquakes occurred, only at 6-hour intervals coinciding with extremes in the ocean and earth tides; however, the mechanism of triggering, if any, is not clear. Alternative periodic mechanisms based on passive withdrawal or expulsion of supporting magma are suggested. Values of energy, moment, and stress drop are computed from the known source geometry and are found to compare favorably with those estimated from seismic data. Assuming a rather low rigidity, the seismic data are consistent with a cylindrical block of 2 × 1016 grams dropping some 300 meters in approximately 75 dislocation stages, each averaging about 4 meters. In support of this model, a cumulative frequency versus magnitude curve suggests that some 75 earthquakes larger than about Ms = 4.5 were of a different genre than those smaller. Other volcanic phenomena, including eruptions and large explosions, preceded the caldera collapse and were accompanied by minor seismicity. However, major seismicity accompanied only the collapse, which apparently was the only volcanic event that included major ground deformation through shear. References Acharya, H. K., Seismicity of the Galapagos Islands and vicinity, Bull. Seismol. Soc. Amer., 55, 609–617, 1965. 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Publication Year: 1973
Publication Date: 1973-12-10
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 145
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