2022年9月5日四川泸定发生M6.8地震,为研究泸定地震孕震区的应力变化,选取b值、小震调制比和丛集率这3个参数,对泸定地震前的区域地震活动状态进行计算研究。结果显示:泸定及周边区域几次强震发生前,区域地震活动均存在持续时间较长的低b值时段,且在低b值状态下震前短期内出现小震高丛集、高调制比的现象; 鲜水河断裂带的地震活动状态分析显示,此次泸定地震前该断裂带存在持续时间近10个月的低b值状态,且短期内出现丛集率升高、调制比高值现象。通过对比分析,认为泸定地震是鲜水河断裂带构造运动的结果。综合分析认为,结合应力场背景和构造条件研究地震活动b值、固体潮调制比和丛集率的时空变化有助于理解大地震的孕育演化过程。

On September 5,2022,a magnitude 6.8 earthquake occurred in Luding,Sichuan Province. In order to study the stress variation in the seismogenic zone of Luding earthquake,in this paper we selected three parameters,namely,b value,small earthquake modulation ratio and clustering rate,to calculate and study the regional seismicity prior to the Luding earthquake. The results are as follows. Before several strong earthquakes occurred in Luding and its surrounding areas,the regional seismicity had a long duration of low b value period,and the phenomenon of high clustering of small earthquakes and high modulation ratio appeared in the short term before earthquakes in the low b value state. The analysis of the seismic activity state of the Xianshuihe fault zone shows that before the Luding earthquake,the fault zone had a low b value state that lasted for nearly 10 months,and in the short term,the clustering rate increased and the modulation ratio increased. Through comparative analysis,it is believed that the Luding earthquake is the result of the tectonic movement of the Xianshuihe fault zone. The analysis shows that the temporal and spatial variation of b value,modulation ratio and clustering ratio of seismicity combined with the background of stress field is helpful to study the evolution process of large earthquakes.

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中国地震科学实验场地震可预测性国际合作项目(2018YFE0109700)、山东省地震局科研基金项目(JJ1805Y)与山东省地震局科技创新团队共同资助