巴颜喀拉块体东-南边界强震序列库仑应力触发过程

Coulomb Stress Triggering Process of Major Earthquake Sequence in the Eastern and Southern Boundaries of the Bayan Har Block

计算和研究了1973—2014年发生在巴颜喀拉块体东-南边界断裂带上的、由9次M_S≥6.3地震组成的强震序列引起的库仑静应力变化图像,分析序列中先发地震破裂对后发地震的应力触发作用。结果表明:(1)1973—1976年在巴颜喀拉块体东边界的虎牙断裂带上发生的4次强震存在着显著的应力触发关系,同时改变了龙门山断裂带中南段及周围区域的应力状态,相继触发了汶川M_S8.0地震和芦山M_S7.0地震;(2)南边界鲜水河断裂带自1973年以来发生的3次强震同样存在应力触发关系,2014年康定M_S6.3地震是巴颜喀拉块体东、南边界强震活动导致的库仑应力变化共同触发的结果;(3)序列中9次地震共同产生的库仑应力变化图像显示:龙门山断裂带南段的汶川地震至芦山地震破裂段之间的空区,鲜水河断裂带南段的道孚地震至康定地震破裂段之间的空区以及鲜水河断裂带、安宁河断裂带、龙门山断裂带交汇的三岔口地区均在库仑应力增加区的覆盖范围之内,需要重点关注。

In this paper, we calculate and map the patterns of Coulomb static stress changes induced by a major earth- quake sequence of 9 Ms I〉 6.3 events in the eastern and southern boundary fault zones of the Bayan Har block from 1973 to 2014, and analyze the effects of stress triggering induced by the preceding events to the following events. The results show that, firstly, there is a significant stress triggering relationship in the 4 major earth- quakes occurred on Huya fault zone in the eastern boundary of the Bayan Har block from 1973 to 1976, besides, it changed the stress state of the middle - south segment of Longmenshan fault zone as well as surrounding areas, and triggered Wenchuan Ms8.0 earthquake and Lushan Ms7.0 earthquake one after another; Secondly, there is also coulomb stress triggering relationship existed in the 3 major earthquakes occurred on Xianshuihe fault zone in the southern boundary of Bayan Har block since 1973, and 2014 Kangding Ms6. 3 earthquake is a common trig- gering result of coulomb stress change induced by strong earthquake activities in both Bayan Har block＇s eastem and southern boundaries; Third/y, the patterns of coulomb stress change caused by the 9 earthquake in the se- quence show that, the seismic gap between Wenchuan earthquake and Lushan earthquake in south segment of Longmenshan fault zone, the seismic gap between Daofu earthquake and Kangding earthquake in Xianshuihe fault zone, and the junction region of Xianshuihe - Anninghe - Longmenshan fault zones are all in the increased zone of Coulomb stress changes, thus their future earthquake risks are worth concem.