The M(s)=7.3 1992 Suusamyr, Kyrgyzstan, earthquake .1. Constraints on fault geometry and source parameters based on aftershocks and body-wave modeling

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Bulletin of the Seismological Society of America
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We investigated the Suusamyr, Kyrgyzstan, earthquake of 19 August 1992, using aftershock data, teleseismic body-wave modeling, and field observations. Aftershocks were recorded by the IRIS Kyrgyzstan broadband network, a temporary six-station aftershock network, and a regional network operated by the Kyrgyz Institute of Seismology. The aftershocks, which range in depth from the surface to 18 km, defined a 50 +/- 10-km-long rupture zone that dips 50 degrees +/- 13 degrees to the south and strikes roughly east-west. The base of the eastern end of the aftershock zone shallowed to the east along strike and may represent a lateral ramp. The surface ruptures also had an east-west strike and dipped south, but the total length (less than 4 km) was much shorter than the aftershock zone. A teleseismic body-wave inversion, using a point source and a directivity correction, yields a focal mechanism with a strike of 221 degrees, dip of 46 degrees, and a slip of 43 degrees. We obtained a moment of 4.1 x 10(19) N-m with a centroid depth between 5 and 21 km. The rupture propagated along an azimuth of 330 degrees +/- 60 degrees, which matches the relative location of the mainshock with respect to the aftershock zone. The results of the aftershock study and teleseismic inversion yield a clear picture of the fault geometry of a large-thrust earthquake.


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