Aftershocks of the 13 May 1993 Shumagin Alaska earthquake

Geophysical Research Letters
By: , and 



The 13 May 1993 Ms 6.9 Shumagin earthquake had an aftershock sequence of 247 earthquakes with magnitudes greater than or equal to 1.5 by 1 June 1993. Of these aftershocks, 79 were located by using S-P travel times at the only two stations within 570 km of the mainshock epicenter. The rupture area inferred from the aftershocks is about 600 km2 and we estimate for the mainshock a mean fault displacement of 1.0 m and a 28 bar stress drop. The magnitude-frequency plots give a b-value for the aftershock sequence of about 0.4, which is low compared to the background value of approximately 0.8. The decay of the aftershock sequence followed the modified Omori law with a p-value of 0.79, which is also lower than the typical values of about 1.1 observed in Alaska. Both of these facts can be interpreted as indicating relatively high ambient stress in the Shumagin seismic gap and the possibility that the 13 May earthquake was a foreshock to a larger gap-filling event to occur within the next few years.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Aftershocks of the 13 May 1993 Shumagin Alaska earthquake
Series title Geophysical Research Letters
DOI 10.1029/94GL00332
Volume 21
Issue 6
Year Published 1994
Language English
Publisher Wiley
Description 4 p.
First page 497
Last page 500
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