| 2015年尼泊尔MW7.9地震应力状态与余震空间分布规律 |
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| 引用本文： | 刘博研,史保平,雷建设.2015年尼泊尔MW7.9地震应力状态与余震空间分布规律[J].地球物理学报,2016,59(6):2094-2102. |
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| 作者姓名： | 刘博研 史保平 雷建设 |
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| 作者单位： | 1. 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;2. 中国科学院大学地球科学学院, 北京 100049 |
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| 基金项目： | 中国地震局地壳应力研究所中央级公益性科研院所基本科研业务专项(ZDJ2013-13),国家青年科学基金项目(41404044),中国地震局尼泊尔地震科考项目共同资助. |
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| 摘 要： | 本文利用2015年尼泊尔MW7.9地震断层面滑动位移分布的运动学反演结果,通过傅里叶变换法得到了主断层面上的两分量应力状态,并研究了余震的空间分布和断层面上应力状态之间的关系.发现滑动位移分布与应力状态分布都相对较为集中,大约70%的余震分布在应力变化为正的区域,而其余发生在应力降区域的余震,又大多发生在应力变化梯度较大的地区.为了得到一个更符合实际的滑动模型来解释余震的触发机制,我们计算了波数域中滑动位移和应力状态的傅里叶谱,发现此次地震的滑动位移和应力状态近似满足k-3和k-2衰减.我们利用简化的圆盘模型说明了非均匀应力变化下的衰减过程,计算了圆盘模型的有效半径re约等于0.7倍的圆盘半径.这就说明圆盘模型中应力增加的部分应该占整个圆盘破裂面积的51%.在本次尼泊尔MW7.9地震实例中,断层面上应力状态为负的区域比滑动位移为正的区域有了明显地缩小.事实表明,余震可以发生在有滑动位移的区域,非均匀应力降模型比均匀应力降模型更加接近真实的震源破裂过程.
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| 关 键 词： | 余震 滑动位移 非均匀应力变化 圆盘模型 |
| 收稿时间： | 2015-12-18 |
Spatial relation between source properties and aftershock distribution of the 2015 MW7.9 Nepal earthquake |
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| LIU Bo-Yan,SHI Bao-Ping,LEI Jian-She.Spatial relation between source properties and aftershock distribution of the 2015 MW7.9 Nepal earthquake[J].Chinese Journal of Geophysics,2016,59(6):2094-2102. |
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| Authors: | LIU Bo-Yan SHI Bao-Ping LEI Jian-She |
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| Institution: | 1. Key Laboratory of Crustal Dynamics, Institute of Crustal Dynamics, China Earthquake Administration, Beijing 100085, China;2. College of Earth Science, University of Chinese Academy of Sciences, Beijing 100049, China |
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| Abstract: | Using the aftershock catalog from the 2015 MW7.9 Nepal earthquake, we examined where the aftershocks occurred relative to the spatial distribution of the stress change based on kinematic source inversion of the fault slip distribution along the main fault. The patterns of the source slip and stress change distributions were much more concentrated and isolated on the main fault plane. About 70% of aftershocks with M>3.0 occurred in the stress increasing area, while a few aftershocks occurred in the area where stress dropped but with high stress change gradient. To obtain a source slip model to explain the aftershock triggering mechanism, we calculated the source spectrums of slip and stress change in the wave-number domain. The resultant spectrum patterns of slip and stress change on the main fault exhibited decay rates of approximately k-3 and k-2, respectively. We calculate the equilibrium radius re which indicates where the stress drop changes its sign, is approximately 0.7a and the area with a positive stress drop is approximately 51% of the total area of the asperity patch. This result indicates that a circular quadratic stress drop model is appropriate for characterizing the rupture process of the Nepal earthquake. This model shows that a positive stress change can occur in regions where a slip displacement exists, which implies that the aftershock might occur in the main fault slip zone, partially explaining the spatially distributed aftershock pattern. Furthermore, the circular quadratic stress drop model more accurately represented the source rupture behavior of the 2015 Nepal earthquake than the circular constant stress drop model. |
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| Keywords: | Aftershock Slip distribution Non-uniform stress change model Circular model |
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