2014年云南鲁甸地震同震库仑应力对余震分布及周边断层的影响

doi:10.3969/j.issn.0253-4967.2015.04.012

摘要/Abstract

摘要：

利用弹性位错理论和分层岩石圈模型, 计算了2014年8月3日发生的M_S6.5云南鲁甸地震导致的同震库仑应力变化场, 讨论了主震对余震分布以及对周边主要活动断层的影响。结果表明: 1)基于NNW向破裂面计算得到的应力变化场能够更好地解释余震的空间分布, 可能为主震的破裂面; 2)目前余震主要沿主破裂面及破裂面以西的应力增强区分布, 其他没有余震记录的应力增强区构造应力积累可能较低; 3)鲁甸地震提升了昭通断裂南段、则木河-小江断裂巧家段以及莲峰断裂NE段上的库仑应力增量, 地震危险性有所增强。这些结果对于判断余震可能发生的区域、圈定震区周边未来可能的地震危险区, 对于灾区人员安置、灾后恢复重建, 以及加强震灾和次生灾害防御具有重要的参考价值。

关键词: 鲁甸地震, 库仑破裂应力, 地震触发, 地震危险性

Abstract:

The studies of earthquake stress transfer and its influence on regional seismicity have found that earthquake occurrences are highly interactive and correlated rather than isolated and random in traditional point in recently years. A lot of phenomena in earthquake observations such as aftershock distribution, stress shadow, earthquake interaction and migration were well explained based on the theory of earthquake stress interaction. It is important that understanding the process of earthquake interaction could give an insight into the physical mechanism of earthquake cycle, and could help us assess the seismic hazard in future.It has long been recognized that regional stress accumulated by tectonic motion is released when earthquake occurs. When earthquakes occur, the accumulated stress does not vanish completely, but is redistributed through the process of stress transfer, and then the redistributed stress may trigger potential earthquakes. The increment of Coulomb failure stress loading in the certain regions may improve the seismic activities. By contrast, the decrement of Coulomb failure stress in the areas of stress shadow where the stress on faults may unload could lead to the decrement of seismic activities.On August 3, 2014, an M_S6.5 earthquake occurred in Zhaotong-Ludian region, Yunnan Province, China, killing and injuring hundreds of people. Therefore, it is critical to outline the areas with potential aftershocks before reconstruction and re-settlement so as to avoid future disasters. Based on the elastic dislocation theory and multi-layered lithospheric model, we calculate the co-stress changes caused by the Zhaotong-Ludian earthquakes to discuss its influences on aftershock distribution and surrounding faults. It is shown that the Coulomb stress changes based on the rupture in the NNW direction can explain better the aftershock distribution. It indicates that the NNW direction may represent the real rupture. The aftershocks mainly distribute in the regions with increased stress along main rupture and west to the rupture. In other regions with increased stress, the distributions of aftershock are rare which may indicate the low tectonic stress accumulation in these regions. The stress accumulation and corresponding seismic hazard on the southern part of Zhaotong Fault, Qiaojia segment of Zemuhe-Xiaojiang Fault and northeastern part of Lianfeng Fault are further increased by the Zhaotong-Ludian earthquake. We should pay special attention to the southern part of Zhaotong Fault where seismic activity is very high in recently years and the increment of Coulomb failure stress in this area is more than 0.1bar(0.1bar is the threshold of earthquake triggering). In order to make a more objective and comprehensive discussion, we calculate the sensitivity of the parameters such as effective coefficient of friction, the calculated depth and multilayered crustal model.

Key words: Zhaotong-Ludian earthquake, Coulomb failure stress, earthquake triggering, seismic hazard

中图分类号:

P315.2

付芮, 单斌, 熊熊, 郑勇, 谢祖军, 刘成利, 房立华. 2014年云南鲁甸地震同震库仑应力对余震分布及周边断层的影响[J]. 地震地质, 2015, 37(4): 1084-1095.

FU Rui, SHAN Bin, XIONG Xiong, ZHENG Yong, XIE Zu-jun, LIU Cheng-li, FANG Li-hua. co-seismic coulomb stress changes and its influences on aftershock distribution and surrounding faults caused by 2014 ludian earthquake, yunnan[J]. SEISMOLOGY AND GEOLOGY, 2015, 37(4): 1084-1095.

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