Earthquake swarm along the San Andreas fault near Palmdale, Southern California, 1976 to 1977

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Abstract

Between November 1976 and November 1977 a swarm of small earthquakes (local magnitude ≤ 3) occurred on or near the San Andreas fault near Palmdale, California. This swarm was the first observed along this section of the San Andreas since cataloging of instrumental data began in 1932. The activity followed partial subsidence of the 35-centimeter vertical crustal uplift known as the Palmdale bulge along this "locked" section of the San Andreas, which last broke in the great (surface-wave magnitude = 8¼;+) 1857 Fort Tejon earthquake. The swarm events exhibit characteristics previously observed for some foreshock sequences, such as tight clustering of hypocenters and time-dependent rotations of stress axes inferred from focal mechanisms. However, because of our present lack of understanding of the processes that precede earthquake faulting, the implications of the swarm for future large earthquakes on the San Andreas fault are unknown.

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Publication type Article
Publication Subtype Journal Article
Title Earthquake swarm along the San Andreas fault near Palmdale, Southern California, 1976 to 1977
Series title Science
DOI 10.1126/science.201.4358.814
Volume 201
Issue 4358
Year Published 1978
Language English
Publisher American Association for the Advancement of Science
Description 4 p.
First page 814
Last page 817
Country United States
State California
City Palmdale
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