| 2015尼泊尔M_S8.1地震中等余震震源机制研究 |
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| 引用本文： | 张广伟,雷建设.2015尼泊尔M_S8.1地震中等余震震源机制研究[J].地球物理学报,2015,58(11):4298-4304. |
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| 作者姓名： | 张广伟 雷建设 |
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| 作者单位： | 中国地震局地壳应力研究所(地壳动力学重点实验室), 北京 100085 |
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| 基金项目： | 中国地震局尼泊尔地震科考、基本科研业务专项(ZDJ2013-12)和国家自然科学基金(41274059)资助. |
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| 摘 要： | 本研究利用西藏台网记录的波形数据,采用gCAP方法反演了2015年4月25日尼泊尔MS8.1大震5次中等余震(5.0≤MS≤6.5)及西藏定日MS5.9地震震源机制解.结果显示,6次地震包含2个正断、2个走滑及2个逆冲型地震.其中2个正断型地震位于主震的东北方向,即发震断层的上盘,表明该区域受到主震同震位移的影响,表现出应力拉张的变化特征;2个走滑型地震在主震破裂的东南方向上,说明随着破裂往东南方向延伸,余震的走滑分量增强;另外2个逆冲型地震位于5月12日MS7.5强余震区域,与MS7.5地震的滑移状态一致,可能与主震同震位移引起该区域处于应力挤压状态密切相关.这些结果表明,尼泊尔MS8.1主震发生后,由于同震位移的影响,不同区域处于不同的应力状态,从而使中等余震表现出不同的震源类型.
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| 关 键 词： | 震源机制解 中等地震 尼泊尔MS8.1地震 gCAP方法 |
| 收稿时间： | 2015-06-12 |
Focal mechanism solutions of moderate-sized aftershocks of the 2015 MS8.1 Nepal earthquake |
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| ZHANG Guang-Wei,LEI Jian-She.Focal mechanism solutions of moderate-sized aftershocks of the 2015 MS8.1 Nepal earthquake[J].Chinese Journal of Geophysics,2015,58(11):4298-4304. |
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| Authors: | ZHANG Guang-Wei LEI Jian-She |
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| Institution: | Key Laboratory of Crustal Dynamics, Institute of Crustal Dynamics, China Earthquake Administration, Beijing 100085, China |
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| Abstract: | On April 25, 2015, an earthquakes with magnitude 8.1(MS) occurred in Nepal, which killed more than 7566 people and caused more than 14500 injures. Its epicentre is located at about 20 km depth, and it is considered as a shallow earthquake with tremendous damages. The earthquake also triggered an avalanche on the Himalaya mountain, and buried parts of the base camp. It is the worst natural disaster to strike Nepal since the 1934 Nepal-Bihar earthquake in the region. There were three strong aftershocks (MS≥7.0) and some moderate aftershocks (5.0≤MS≤6.5) that occurred on the same fault. In this paper, we determined the focal mechanism solutions of six moderate-sized aftershocks having better recordings at the seismic stations in order to better understand the rupture characteristics of this large earthquake.#br#Using the digitally broadband seismic data recorded by the Xizang network stations, we obtained focal mechanisms of six moderate-sized earthquakes with the generalized Cut and Paste (gCAP) inversion method. This method divides three-componental waveforms into Pnl and surface wave segments, and allows adjustable time shifts between observed and synthetic waveforms, which reduce the influence of uncertainties in the 1-D velocity model used. #br# Our results show that the six moderate-sized earthquakes present different source types, two events for normal types, two events for strike-slip types, while the rest two events for thrust-fault types. The six earthquakes with different types are located at different regions, respectively. The two normal-fault earthquakes are distributed to the northeast of the mainshock and they are situated in the hanging wall of the fault. These normal-fault sources may be due to the tension stress change caused by the coseismic slip. The two strike-slip sources are located between the mainshock and the May 12 MS7.5 strong aftershocks, suggesting that the strike-slip component is getting larger with the southeast extension of the fault. The two thrust-fault earthquakes are also interpreted as a compressional stress change due to the mainshock coseismic slip. Intergrating these focal mechanism solutions with the aftershock distribution, we conclude that different source types of these moderate-sized earthquakes in different regions all might be due to different stress regime caused by the coseismic displacement. |
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| Keywords: | Focal mechanism Moderate-sized earthquake Nepal MS8 1 earthquake gCAP method |
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