Rise time and source duration of the 2008 M-W 7.9 Wenchuan (China) earthquake as revealed by Rayleigh waves

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Title:	Rise time and source duration of the 2008 M-W 7.9 Wenchuan (China) earthquake as revealed by Rayleigh waves
Authors:	Hwang, RD (Hwang, Ruey-Der) Chang, JP (Chang, Jo-Pan) Wang, CY (Wang, Chien-Yin) Wu, JJ (Wu, Jia-Jhang) Kuo, CH (Kuo, Ching-Huei) Tsai, YW (Tsai, Yu-Wei) Chang, WY (Chang, Wen-Yen) Lin, TW (Lin, Tzu-Wei)
Contributors:	Dept Geol
Keywords:	Rise time source duration Rayleigh waves phase velocity rupture directivity
Date:	2011
Issue Date:	2013-01-31 13:16:31 (UTC+8)
Abstract:	The fault parameters of the 2008 Wenchuan earthquake were studied in a rupture directivity analysis by simultaneously inverting the period of the first Fourier spectral-node and the 100-s phase-delay time of the Rayleigh wave. The results show that the earthquake is a unilateral event with an optimal rupture azimuth of N59 degrees E, consistent with the distribution of aftershocks. They also indicate that the fault plane strike is in the NE-SW direction, corresponding to the fault plane strike of 238 degrees and NW-dipping (reported by the USGS). The inversion shows the source duration (including the rise time and rupture time) and rise time are 70 +/- 0.8 s and 9.3 +/- 0.6 s, respectively. The rupture velocity estimated only from the rupture time exhibits relatively higher value, 3.45 +/- 0.10 km/s, close to or larger than the S-wave velocity in the crust. One possible cause is that the rupture mechanism transferred from the thrust faulting in the southwestern portion of the fault to the strike-slip faulting in the northeastern one. The rise time offers an estimate of the dynamic stress drop (37.8 +/- 2.3 bars), from which through a macroscopic view the radiated seismic energy of (5.93 +/- 0.4) x 10(16) N m is calculated. Although the estimated rupture length (similar to 210 km) and source duration are shorter than several source rupture models, the current analyses show the first-order rupture feature of the 2008 Wenchuan earthquake rupturing the Longmenshan fault zone.
Relation:	EARTH PLANETS AND SPACE 卷: 63 期: 5 頁數: 427-434
Appears in Collections:	[Department of Geography & Graduate Institute of Earth Science / Geography ] journal articles

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