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2015年4月25日在喜马拉雅弧的尼泊尔博克拉发生8.1级大地震,2015年4月25日至5月12日相继发生尼泊尔7.0、7.1和7.5级大震。根据西藏地震台网资料和收集到的国内外相关资料,分析了尼泊尔8.1级地震的基本参数、余震分布、序列衰减以及喜马拉雅弧的历史破裂等特征。结果表明:尼泊尔8.1、7.0、7.1和7.5级地震的震源力学机制均显示为低倾角的纯逆冲性事件,破裂面走向平行于NWW—SEE的喜马拉雅边界,以5°~11°倾向北;从定性的角度分析,尼泊尔8.1级地震可判定为独特的主—余型地震,其余震分布长轴走向显示与喜马拉雅主边界走向一致,密集区NWW—SEE向长轴和S—N向短轴大约分别为200 km和150 km;估计2015年尼泊尔8.1级地震破裂尺度与1833年尼泊尔加德满都北部大震相当,比1934年的尼泊尔—印度(比哈尔邦)间大震略小。据历史地震破裂空段推测,2015年尼泊尔8.1级地震破裂填充在1505年大震与1833年大震两次历史破裂之间的空段。
On April 25, 2015, a magnitude 8.1 earthquake struck Pokhara, Nepal, in the Himalayas. From April 25 to May 12, 2015, major earthquakes of magnitude 7.0, 7.1 and 7.5 in Nepal occurred. According to the data of Tibet Seismological Network and relevant data collected at home and abroad, the basic parameters, aftershock distribution, sequence attenuation and historical rupture of Himalayan arc are analyzed. The results show that the focal mechanism of the 8.1, 7.0, 7.1 and 7.5 earthquakes in Nepal are both purely thrust events with low dip angle. The rupture plane is parallel to the NWW-SEE Himalayan boundary and tends to north from 5 ° to 11 °. From a qualitative point of view, the 8.1-magnitude earthquake in Nepal can be identified as a unique main-type residual earthquake. The distribution of the major axis of the remaining shocks is consistent with that of the Himalayan main boundary. The NWW-SEE of the intensive area extends to the major axis and the S-N minor axis About 200 km and 150 km, respectively. It is estimated that the magnitude of the MS8.1 earthquake in 2015 in Nepal was comparable with the large earthquake in northern Nepal in Kathmandu in 1833, slightly less than that in the Great Nepalese-Nepal (Bihar) earthquake in 1934. According to the historical earthquake rupture, it is speculated that the 2015 earthquake of magnitude 8.1 in Nepal fills the empty space between two historical ruptures of the 1505 earthquake and the 1833 earthquake.