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摘要
Characteristics of near-fault velocity pulses during the Wenchuan earthquake are analyzed based on wavelet analysis methods. 64 groups of strong motion records within 200 km to the causative fault are used as database. The amplitude and period characteristics of velocity pulses from Wenchuan earthquake are compared with the Chi-Chi and Northridge earthquake, and the relationships of pulse amplitude and period with magnitude and fault distance are also analyzed. Based on the analysis of near-fault ground motion containing velocity pulses, the following conclusions can be made; (1) The near-fault velocity pulses from Wenchuan earthquake are characterized as long period and low amplitude. The pulse periods are about 6 similar to 14 s, with the largest pulse period reaching 14. 2 s which is recorded by fault parallel component of the 51MZQ station, and the pulse amplitudes are relatively small for the Wenchuan earthquake compared with the Chi-Chi and Northridge earthquake. (2) Large velocity pulses are observed at sites where the rupture propagated toward the recording station and close to rupture projection with fault distance smaller than 30 km. It can be concluded that the recorded long period pulses are mainly caused by forward directivity effects. (3) The pulse periods are logarithmicly linear increasing with the moment magnitude, and the periods have a trend of decreasing with fault distance. The recorded pulse amplitudes vary from 50 similar to 150 cm/s for records with moment magnitude smaller than 7. 5, which is very close to the typical slip velocity 100 cm/s; while for records with magnitude larger than 7. 5, the pulse amplitudes can easily exceed 100 cm/s, and can reach 200 cm/s for some records, which might he correlated with the larger fling-step and site condition in local area.
- 出版日期2012-6
- 单位中国地震局; 中央民族大学
