Publication Date:
2017-03-28
Description:
We perform a comprehensive detection of early aftershocks following the 2013 Mw6.6 Lushan earthquake, which occurred in the southern Longmenshan Fault Zone (LMSF) in Sichuan Province, China, about five years after the 2008 Mw7.9 Wenchuan earthquake. We use events in both standard and relocated catalogs as templates to scan through continuous waveforms 2 days before and 3 days after the mainshock. We successfully reduce the magnitude of completeness M c by more than one order, and obtain up to 6 times more events than listed in both catalogs. Aftershocks in the first hour mostly occur around the mainshock slip region, and aftershocks at later times show systematic expansions in the along-strike, perpendicular-strike, and up-dip directions. Although postseismic deformation following the Lushan mainshock has not been clearly identified, we suggest that early aftershock expansions are likely driven by afterslip of the Lushan mainshock. This is consistent with the observations that most aftershocks were in the stress shadow of the Lushan mainshock, and that there was significant slip deficit in the top 10 km of the crust. We also find that seismicity on the back-thrust fault was activated as soon as 20 minutes after the mainshock, earlier than previously reported. We are unable to detect any clear foreshocks in the last two days before the Lushan mainshock.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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