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Spatial patterns of aftershocks of shallow focus earthquakes in California and implications for deep focus earthquakes

Journal of Geophysical Research

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Abstract

Previous workers have pioneered statistical techniques to study the spatial distribution of aftershocks with respect to the focal mechanism of the main shock. Application of these techniques to deep focus earthquakes failed to show clustering of aftershocks near the nodal planes of the main shocks. To better understand the behaviour of these statistics, this study applies them to the aftershocks of six large shallow focus earthquakes in California (August 6, 1979, Coyote Lake; May 2, 1983, Coalinga; April 24, 1984, Morgan Hill; August 4, 1985, Kettleman Hills; July 8, 1986, North Palm Springs; and October 1, 1987, Whittier Narrows). The large number of aftershocks accurately located by dense local networks allows us to treat these aftershock sequences individually instead of combining them, as was done for the deep earthquakes. The results for individual sequences show significant clustering about the closest nodal plane and the strike direction for five of the sequences and about the presumed fault plane for all six sequences. This implies that the previously developed method does work properly. The reasons for the lack of clustering about main shock nodal planes for deep focus aftershocks are discussed. -from Author

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Spatial patterns of aftershocks of shallow focus earthquakes in California and implications for deep focus earthquakes
Series title:
Journal of Geophysical Research
Volume
94
Issue:
B5
Year Published:
1989
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Geophysical Research
First page:
5615
Last page:
5626