【摘要】 2013年4月20日芦山MS7.0地震发生在龙门山断裂带的西南段,距2008年汶川MS8.0地震仅约85km,时间上仅相隔5年.首先计算了汶川地震的静态库仑应力变化对本次芦山地震的影响,得出芦山地震是由汶川地震触发造成的(库仑应力上升了0.012 MPa);进一步计算了芦山地震与汶川地震这两次大地震共同产生的静态库仑应力变化.结果表明,芦山地震的余震受前面两次大地震的共同影响,而不仅仅是芦山地震单独作用的结果,超过85%的余震发生在两次地震共同产生的静态库仑应力变化增大的地方,而芦山地震本身触发不了本次的余震序列(仅48.7%的余震位于主震所产生的应力加载区).此外,计算结果表明芦山地震本身对周边断层影响较小,仅龙门山断裂带的东北段受到一定的加载作用;而由于汶川地震的作用,安宁河断裂、大凉山断裂、马尔康断裂、岷江断裂和虎牙断裂呈卸载趋势,仅鲜水河断裂东南段和龙门山断裂中段受到加载作用,这均会加速断层上新地震的发生.更多还原

【Abstract】 On 20 April 2013,a MS7.0 earthquake struck Lushan County,Sichuan Province.The epicenter is on the southwest segment of the Longmenshan fault zone which is only about 85 km from the 2008 Wenchuan MS8.0 earthquake only after 5 years.This paper first calculated the impact of Coulombstress change induced by the Wenchuan earthquake on the Lushan earthquake,and found that the Lushan earthquake have been triggered by the Wenchuan earthquake(Coulomb stress increased by 0.012 MPa).Then the Coulomb stress change generated by the Lushan earthquake and the Wenchuan earthquake were calculated.The results show that the aftershocks have been promoted by the combined effect of the two strong earthquakes.More than 85% of the aftershocks occurred in the Coulomb stress increasing region.However,the Lushan earthquake alone cannot trigger the aftershock sequence(only 48.7% aftershocks fall into the increasing region).Furthermore,the calculation result also indicate that the Lushan earthquake has little influence on the surrounding faults.Only the northeast segment of the Longmenshan fault is brought closer to failure.Due to the Wenchuan earthquake,most of the surrounding faults,such as the Anninghe,Daliangshan,Barkam,Minjiang and Huya faults are being unloaded,while the southeast segment of the Xianshuihe fault and middle segment of the Longmenshan fault are enhanced,accelerating occurrence of new earthquakes.更多还原