Rupture process of the 2003 Bam, Iran, earthquake: Did shallow asperitites on a fresh fault cause extreme ground motions

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ConferenceEOS Trans. American Geophysical Union, December 13-17, 2004, San Francisco, CA, USA
Subjectseismic hazard assessment and prediction; earthquake dynamics and mechanics; earthquake ground motions and engineering; earthquake parameters
AbstractThe Bam, Iran, earthquake on December 26, 2003 caused heavy damage to the city of Bam including the historic heritage of Arg-e-Bam. This Mw6.5 earthquake rupture created fresh faults 5 km westward away from the Bam fault. The Bam strong-motion station recorded 992 gal in the UD component and two directivity pulses in the horizontal components with a dominant frequency of 1 Hz. We inferred the rupture process of the 2003 Bam earthquake from strong motion data observed by BHRC, together with teleseismic data to constrain global features of the source. Waveform inversions using teleseismic data (e.g. Yamanaka, 2003; Yagi, 2003) have suggested the existence of a shallow asperity. Nakamura et al. (2004) estimated aftershock distribution with vertical dipping that superimposed the fresh faults, not the Bam fault. They proposed fault planes consisting N-S alignment with northward branches beneath the city of Bam. Our preliminary analyses show that two directivity pulses are created by northward rupture near the hypocenter and north-eastward rupture beneath the city. Recent earthquakes occurred on immature faults with shallow asperities have also generated localized extreme-strong motions (e.g., 2003 Miyagi-ken Hokubu, Japan, with Mw6.1; 2000 Tottori, Japan, with Mw6.6). Larger fracture energy is expected for shallow asperities on immature faults than those on mature faults. For example, the 2000 Tottori earthquake has several times larger fracture energy than expected by the scaling between seismic moment and fracture energy. When considering the energy budget, are radiated energy from the immature faults enough to generate the extreme ground motions? Detailed source process inversions might be able to answer this question.
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NPARC number21274179
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Record identifierb066212f-80bb-44a7-961b-663c6eaafd34
Record created2015-02-24
Record modified2016-05-09
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