2015年尼泊尔M_W7.9地震应力状态与余震空间分布规律

发布时间：2018-02-02 10:27

本文关键词： 余震滑动位移非均匀应力变化圆盘模型　出处：《地球物理学报》2016年06期 　论文类型：期刊论文

【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.
[Abstract]:Based on the kinematic inversion results of the slip displacement distribution on the fault plane of the MW7.9 earthquake in Nepal on 2015, the two-component stress state on the main fault plane is obtained by Fourier transform method. The relationship between the spatial distribution of aftershocks and the stress state on the fault plane is studied. It is found that the distribution of sliding displacement and stress state are relatively concentrated, and about 70% of the aftershocks are distributed in the region where the stress change is positive. In order to obtain a more realistic sliding model to explain the trigger mechanism of aftershocks, most of the remaining aftershocks occurred in the regions with large stress gradient. The Fourier spectra of sliding displacement and stress state in wavenumber domain are calculated. It is found that the sliding displacement and stress state of the earthquake approximately satisfy the k-3 and k-2 attenuation. We use the simplified disk model to illustrate the attenuation process under the inhomogeneous stress variation. The effective radius re of the disc model is calculated to be about 0.7 times the radius of the disk. This means that the stress increase in the disc model should account for 51% of the whole disc rupture area. In this case, the Nepal MW7.9. In an earthquake. The region with negative stress state on fault plane is obviously smaller than that with positive sliding displacement. The facts show that aftershocks can occur in areas with sliding displacement. The nonuniform stress drop model is closer to the real source rupture process than the uniform stress drop model.
【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);中国科学院大学地球科学学院;
【基金】：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
【分类号】：P315
【正文快照】： 1引言北京时间2015年4月25日14点11分26秒,临近我国西藏自治区的尼泊尔境内发生了MW7.9强烈地震.UGSG测定震源位置为28.147°N,84.708°E,震源深度15km.震中位于尼泊尔博克拉市,距离首都加德满都西北77km处,是自1950年MW8.7察隅地震以后尼泊尔近70年来受到影响最大的地震(Mitt

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