地震研究

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 Apr.25, 2015, an Nepal M8.1 strong earthquake in the Pokhara of Nepal occurred on the Himalayan arc. The three strong events of M7.0, M7.1 and M7.5 had occurred in Nepal from Apr.25 to May.12, 2015. According to the data of Tibet Seismic Network and the current correlative information from internal and overseas, we analyzed the basic seismic parameters, aftershock distribution and sequence attenuation of Nepal M8.1 earthquake, and other characteristics of historical rupture along Himalayan arc. The results show that the focal mechanisms of the Nepal M8.1, M7.0, M7.1 and M7.5 earthquakes are almost the pure thrust events with a low-angle and shown as the rupture plane strikes parallel to the Himalayan belt in NWW-SEE, and the dips with 5°～11° to the NNE. From a qualitative point of view, the Nepal M8.1 earthquake can be determined a typical main shock-aftershock sequence. The trend of the long axis of aftershocks distribution ellipsoid was consistent with the trend of main boundary of Himalayan belt structural. The lengths of the long axis in NWW-SEE and short axis in S—N of the aftershocks distribution ellipsoid are about 200 km and 150 km respectively. It is estimated that the rupture zone of the 2015 M8.1 Nepal earthquake is similar to that of the 1833 M_W7.7 Nepal earthquake in the North of Kathmandu, and is smaller than that of the 1934 M_W8.1 Nepal-India(Bihar)earthquake. From the historical seismic gap, the rupture zone of the 2015 M8.1 Nepal earthquake filled the seismic gap between the two historical rupture of the 1505 earthquake and the 1833 earthquake.

引言
1 地震基本参数与震源破裂特征
2 尼泊尔8.1级地震序列特征
3 尼泊尔8.1级地震与喜马拉雅历史破裂
4 讨论与结论

表1 全球各机构测定2015年4月25日尼泊尔8.1级地震基本参数<br/>Tab.1 Basic parameters of Nepal M8.1 earthquake on Apr.25, 2015 by each institution in the world

表1 全球各机构测定2015年4月25日尼泊尔8.1级地震基本参数
Tab.1 Basic parameters of Nepal M8.1 earthquake on Apr.25, 2015 by each institution in the world

表2 2015年4月25日尼泊尔8.1级地震的矩张量解<br/>Tab.2 Moment tensor solution of the Nepal M8.1 earthquake on Apr.25, 2015

表2 2015年4月25日尼泊尔8.1级地震的矩张量解
Tab.2 Moment tensor solution of the Nepal M8.1 earthquake on Apr.25, 2015

表3 尼泊尔7.0级、7.1级和7.5级强余震矩张量解<br/>Tab.3 Moment tensor solutions of the Nepal M7.0,M7.1 and M7.5 aftershocks

表3 尼泊尔7.0级、7.1级和7.5级强余震矩张量解
Tab.3 Moment tensor solutions of the Nepal M7.0,M7.1 and M7.5 aftershocks

表4 2015年4月25日尼泊尔8.1级地震序列目录(M≥5.0)<br/>Tab.4 Catalogue of Nepal M8.1 earthquake sequence on Apr.25, 2015(M≥5.0)

表4 2015年4月25日尼泊尔8.1级地震序列目录(M≥5.0)
Tab.4 Catalogue of Nepal M8.1 earthquake sequence on Apr.25, 2015(M≥5.0)

图1 尼泊尔8.1级地震序列的M-t图(a)、N-t图(b)、蠕变图(c)<br/>Fig.1 M-t diagram(a),N-t diagram(b)and curve of strain release(c)of the Nepal M8.1 earthquake sequence

图1 尼泊尔8.1级地震序列的M-t图(a)、N-t图(b)、蠕变图(c)
Fig.1 M-t diagram(a),N-t diagram(b)and curve of strain release(c)of the Nepal M8.1 earthquake sequence

图2 尼泊尔8.1级地震ML≥3.0余震分布<br/>Fig.2 The distribution of the ML≥3.0 aftershocks of Nepal M8.1 earthquake

图2 尼泊尔8.1级地震ML≥3.0余震分布
Fig.2 The distribution of the ML≥3.0 aftershocks of Nepal M8.1 earthquake

表5 喜马拉雅弧历史大震目录<br/>Tab.5 Catalog of historical earthquakes along the Himalayan Arc

表5 喜马拉雅弧历史大震目录
Tab.5 Catalog of historical earthquakes along the Himalayan Arc

图3 尼泊尔8.1级地震与喜马拉雅主要历史破裂和强震分布(据Bilham, Ambraseys(2005); Chander(1989); Jackson(2002); Ambraseys, Jackson(2003); Bilham(2004))<br/>Fig.3 Distribution of Nepal M8.1 earthquake and the main history ruptures and strong earthquakes along Himalaya(drawn from Bilham, Ambraseys(2005); Chander(1989); Jackson(2002); Ambraseys,Jackson(2003); Bilham(2004))

图3 尼泊尔8.1级地震与喜马拉雅主要历史破裂和强震分布(据Bilham, Ambraseys(2005); Chander(1989); Jackson(2002); Ambraseys, Jackson(2003); Bilham(2004))
Fig.3 Distribution of Nepal M8.1 earthquake and the main history ruptures and strong earthquakes along Himalaya(drawn from Bilham, Ambraseys(2005); Chander(1989); Jackson(2002); Ambraseys,Jackson(2003); Bilham(2004))

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备注

引言

1 地震基本参数与震源破裂特征

2 尼泊尔8.1级地震序列特征

3 尼泊尔8.1级地震与喜马拉雅历史破裂

4 讨论与结论

期刊信息