CONSTRAINING THE FOCAL MECHANISM OF THE 2015 NEPAL EARTHQUAKE WITH OBSERVATIONS OF THE CONTINUOUS GRAVITY STATIONS

doi:10.3969/j.issn.0253-4967.2016.03.012

SEISMOLOGY AND GEOLOGY ›› 2016, Vol. 38 ›› Issue (3): 660-669.DOI: 10.3969/j.issn.0253-4967.2016.03.012

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CONSTRAINING THE FOCAL MECHANISM OF THE 2015 NEPAL EARTHQUAKE WITH OBSERVATIONS OF THE CONTINUOUS GRAVITY STATIONS

JIANG ying^1,2, LIU Zi-wei¹, LI Hui¹, ZHANG Xiao-tong¹, WEI-Jin¹, SHEN Chong-yang¹

1 Key Laboratory of Earthquake Geodesy, Institute of Seismology, China Earthquake Administration, Wuhan 430071, China;
2 State Key Laboratory of Geodesy and Earth's Dynamics, Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan 430077, China

Received:2015-08-28 Revised:2015-10-29 Online:2016-09-20 Published:2016-10-15

基于连续重力观测约束2015年尼泊尔地震的震源机制解

江颖^1,2, 刘子维¹, 李辉¹, 张晓彤¹, 韦进¹, 申重阳¹

1 中国地震局地震研究所, 地震大地测量重点实验室, 武汉 430071;
2 中国科学院测量与地球物理研究所, 大地测量与地球动力学国家重点实验室, 武汉 430077

通讯作者: 刘子维,副研究员,E-mail:liuzw.99@gmail.com
作者简介:江颖,女,1986年生,2014年于中国科学院测量与地球物理研究所获固体地球物理专业博士学位,助理研究员,研究方向为地球自由振荡、重力数据分析及其应用,E-mail:jiangyingchen@126.com。
基金资助:
中国地震局地震研究所基本科研业务费（IS201526225）、大地测量与地球动力学国家重点实验室开放基金（SKLGED201512EZ）和国家自然科学基金（41404064，41374088）共同资助

Abstract

Abstract:

On 25 April 2015, a magnitude M_S8.1 interplate thrust earthquake ruptured a densely instrumented region of Nepal. After earthquake, the focal mechanism solutions of Nepal earthquake were provided by well-respected international earthquake research institutions based on different data and methods, which were different. We compared free oscillations observed by 18 spring gravimeters of continuous gravity stations with synthetic normal modes corresponding to 3 different focal mechanisms for the Nepal earthquake, and the focal mechanisms solutions of Nepal earthquake were analyzed and constrained by spherical normal modes in a 2 to 5mHz frequency band. Based on the optimal focal mechanism, the accurate magnitude was searched. The results show that the focal mechanism of Nepal earthquake can be estimated by spherical modes in the 2 to 5mHz frequency band. The synthetic modes corresponding to the focal mechanism determined by the GCMT Moment Tensor Solution showed agreement to the observed modes, the average of misfit factors F was 0.03, and the average of scaling factors was 1.04, which was closest to 1, suggesting that earthquake magnitudes predicted in this way can reflect the total energy released by the earthquake. Based on the focal mechanism solutions provided by GCMT, keeping the strike, dip, slip, depth constant, adjusting the scalar moment, the real scalar moment was searched. When the average of scaling factors was 1, the average of misfit factors F was only 0.03. After calculation, the scalar moment of Nepal earthquake was 8.09×10²⁰ Nm, and the corresponding magnitude was M_W7.91.

Key words: Nepal earthquake, focal mechanism solutions, Earth's free oscillations, gravimeter observations

摘要：

2015年4月25日，尼泊尔境内发生M_S8.1地震；地震发生之后，国际上一些著名的地震科研机构采用不同的数据和方法计算得到此次地震的震源机制解，但结果存在一定的差异。根据尼泊尔地震现有的3个不同震源机制解模拟计算了该地震激发的自由振荡信号，并与全国连续重力台网中18个弹簧重力仪的观测结果进行比对，基于2~5mHz的球型简正模分析和约束了尼泊尔地震的震源机制解，并基于最佳震源机制解，比对观测值与模拟值，计算更为准确的震级。结果表明，利用弹簧重力仪的观测可以有效地对尼泊尔地震的震源机制解进行总体评估。基于GCMT反演得到的震源机制解的自由振荡模拟值与观测值符合最好，不符合度F的平均值为0.03，比例因子S的平均值为1.04，最接近1，说明其反演的标量地震矩可以较好地反映尼泊尔地震释放的能量。基于GCMT的震源机制解结果，保证断层走向、倾角、滑动方向角和震源深度不变，不断调整标量地震矩的值，搜索最真实可靠的标量地震矩，当观测值与模拟值的比例因子S达到1时，不符合度F也较小，仅有0.03，经计算尼泊尔地震的标量地震矩为8.09×10²⁰ Nm，相应的震级为M_W7.91。

关键词: 尼泊尔地震, 震源机制解, 地球自由振荡, 重力观测

CLC Number:

P315.3

JIANG ying, LIU Zi-wei, LI Hui, ZHANG Xiao-tong, WEI-Jin, SHEN Chong-yang. CONSTRAINING THE FOCAL MECHANISM OF THE 2015 NEPAL EARTHQUAKE WITH OBSERVATIONS OF THE CONTINUOUS GRAVITY STATIONS[J]. SEISMOLOGY AND GEOLOGY, 2016, 38(3): 660-669.

江颖, 刘子维, 李辉, 张晓彤, 韦进, 申重阳. 基于连续重力观测约束2015年尼泊尔地震的震源机制解[J]. 地震地质, 2016, 38(3): 660-669.

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CONSTRAINING THE FOCAL MECHANISM OF THE 2015 NEPAL EARTHQUAKE WITH OBSERVATIONS OF THE CONTINUOUS GRAVITY STATIONS

基于连续重力观测约束2015年尼泊尔地震的震源机制解

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