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Science 26 October 1973:
Vol. 182. no. 4110, pp. 386 - 389
DOI: 10.1126/science.182.4110.386
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Articles

Microearthquakes at St. Augustine Volcano, Alaska, Triggered by Earth Tides

F. J. Mauk 1 and J. Kienle 2

1 Department of Geology and Mineralogy, University of Michigan, Ann Arbor 48104
2 Geophysical Institute, University of Alaska, College 99701

Microearthquake activity at St. Augustine volcano, located at the mouth of Cook Inlet in the Aleutian Islands, has been monitored since August 1970. Both before and after minor eruptive activity on 7 October 1971, numerous shallow-foci microearthquake swarms were recorded. Plots of the hourly frequency of microearthquakes often show a diurnal peaking of activity. A cross correlation of this activity with the calculated magnitudes of tidal acceleration exhibited two prominent phase relationships. The first, and slightly more predominant, phase condition is a phase delay in the microearthquake activity of approximately 1 hour from the time of maximum tidal acceleration. This is thought to be a direct microearthquake-triggering effect caused by tidal stresses. The second is a phase delay in the microearthquake activity of approximately 5 hours, which correlates well with the time of maximum oceanic tidal loading. Correlation of the individual peaks of swarm activity with defined components of the tides suggests that it may be necessary for tidal stressing to have a preferential orientation in order to be an effective trigger of microearthquakes.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Common Features and Peculiarities of the Seismic Activity at Phlegraean Fields, Long Valley, and Vesuvius.
(2001)
Bulletin of the Seismological Society of America 91, 191-205
Aftershocks of the 23 November 1980 Italian earthquake as phenomena induced by the same main earthquake.
L. CASERTANO and A. OLIVERI DEL CASTILLO (1984)
Bulletin of the Seismological Society of America 74, 781-784
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Science. ISSN 0036-8075 (print), 1095-9203 (online)