Moment tensors of earthquakes in and near the Tibetan Plateau and their scaling law |
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Authors: | Si-Hua Zheng and Ziro Suzuki |
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Institution: | (1) Center for Analysis and Prediction, State Seismological Bureau, 100036 Beijing, China;(2) Faculty of Science, Tohoku University, 980 Sendai, Japan;(3) Present address: College of Humanities and Sciences, Nihon University, 156 Tokyo, Japan |
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Abstract: | Moment tensors of eleven major earthquakes in the Tibetan Plateau and its surrounding region from 1966 to 1980 are estimated
by generalized inverse technique. The seismic source time function and focal depth are immediately determined in the inversion.
The results show that moment tensors of some events differ significantly from double couple, the deviation increases with
decreasing plunge angle of null axis. All these events occurred in the upper crust, much shallower than those reported so
far, for example, in NEIS Bulletin. Focal mechanism solution obtained from the moment tensors are consistent with the idea
that the Indian plate collides northwards with the Eurasian plate and that an eastward spreading exists in the crust of the
Tibetan Plateau. The stress drops for earthquakes of intraplate are systematically higher than those of earthquakes in suture
zone. The source process duration becomes longer with seismic moment, but for the same seismic moment, the process duration
for earthquakes in suture zone is about 1.4 times of those for intraplate event, these results suggest that the earthquakes
near suture zone may be of a special characteristics in source process differently from those in intraplate.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 423 – 434, 1992. |
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Keywords: | Tibetan Plateau seismic moment tensor scaling relation |
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