YIN Hao,
SHAN XinJian,
ZHANG YingFeng et al
.2018.Rapid determination of source parameters for the 2008 Wenchuan earthquake constrained by high-rate GPS and strong motion data.Chinese Journal Of Geophysics,61(5): 1806-1816,doi: 10.6038/cjg2018L0527
Rapid determination of source parameters for the 2008 Wenchuan earthquake constrained by high-rate GPS and strong motion data
YIN Hao1,2, SHAN XinJian1, ZHANG YingFeng1, QU ChunYan1, WANG ZhenJie2, LIU XiaoDong1,2, ZHANG GuoHong1, LI YanChuan1
1. State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China; 2. School of Geosciences, China University of Petroleum(East China), Qingdao 266580, China
Abstract：High-rate GPS facilities can detect real-time surface displacement, which has many seismic applications, such as rapid determination of the epicenter locations, earthquake magnitude and intensity, and even earthquake rupture process. In this study, taking the 2008 Wenchuan earthquake as an example, we use data from 7 GPS stations to calculate the epicenter location. We find that the two epicenters determined by high-rate GPS and seismic data are ~15.7 km apart from each other, due to the difference between GPS and seismic waveforms. Comparing the high-rate GPS and accelerograms statistically shows that although GPS data and strong motion record have their own physical meanings, respectively and the peak ground motion recorded by two datasets are obviously different, the PGA, PGV and PGD in GPS data can also be used to calculate seismic intensity. In addition, we correct the baseline bias using the SMBLOC program to obtain surface displacement time series, which can be deemed as equivalent to real-time high-rate GPS data. Based on Okada dislocation and a finite fault segment model, we finally invert the static offset displacement data smoothed from the corrected and integrated strong motion displacement data by a moving window. Our inversion results show that the main seismogenic fault of the Wenchuan earthquake ruptured from southwest to northeast, which is consistent with most of other studies. Furthermore, we try to conduct it in a quasi-real-time way and to rapidly determine the earthquake rupture process of the Wenchuan earthquake. Thus, our result also shows that the first estimated magnitude can be MW7.0 as fast as 20 seconds after the origin time, that is 14∶28∶04. Besides, 70 seconds after the origin time the magnitude estimation of MW7.8 is stable, with the condition that the fault rupture is still going. At last, 159 seconds after the origin time, the Wenchuan event stops according to the displacement time series. The results prove that real-time surface displacement can be used to determine the magnitude and rupture direction of a major earthquake quickly and accurately. High-rate GPS will provide a good complement to the existing earthquake early warning system.
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