Tomography of the source zone of the 2015 M 7.8 Nepal earthquake

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• 作者：Wei Wei^a ; ^b ; ; Dapeng Zhao^b
• 关键词：Seismic tomography ; Seismic anisotropy ; Seismotectonics ; 2015 Nepal earthquake ; Himalaya collision belt
• 刊名：Physics of the Earth and Planetary Interiors
• 出版年：2016
• 出版时间：April 2016
• 年：2016
• 卷：253
• 期：Complete
• 页码：58-63
• 全文大小：1891 K

文摘

We conducted P-wave anisotropic tomography beneath Nepal and surrounding areas to clarify the causal mechanism of the 25 April 2015 Nepal earthquake (Mw 7.8) and dynamic processes of the India-Asia collision zone. Our results show that hypocenters of the 2015 Nepal mainshock and the 1833 Nepal earthquake (M 8.0) are located in a zone with a higher P-wave velocity (high-V), and the high-V zone coincides with the coseismic slip area of the 2015 Nepal mainshock. The high-V zone may reflect a strongly coupled patch (i.e., asperity) in the megathrust zone between the subducting Indian plate and the overlying Eurasian plate. This result suggests that the nucleation of the Nepal earthquakes was controlled by structural heterogeneities in the megathrust zone. Significant variations of P-wave velocity anisotropy are revealed across the Himalaya collision belt. The predominant fast P-wave velocity direction is NE–SW beneath northern India, whereas it becomes NW–SE beneath the Himalaya, suggesting that the fossil anisotropy in the Indian plate is overprinted by the ongoing India-Asia collision.