2017年8月九寨沟MS7.0地震序列S波分裂特征  

Characteristic of S-wave Splitting of the 2017 Jiuzhaigou MS7.0 Earthquake Sequence

作　　者：黄春梅[1] 吴朋[1] 苏金蓉[1] 王宇航[1] 魏娅玲[1] 李大虎[1] 颜利君 HUANG Chunmei;WU Peng;SU Jinrong;WANG Yuhang;WEI Yaling;LI Dahu;YAN Lijun(Sichuan Earthquake Agency,Chengdu 610041,China)

机构地区：[1]四川省地震局,成都610041

出　　处：《华北地震科学》2020年第1期29-37,共9页North China Earthquake Sciences

基　　金：国家重点研发计划(2018YFC1504501-02);四川省地震局紧急地震信息服务创新团队(201801);中国地震局地震科技星火计划攻关项目(XH20051);2018年四川省地震局地震科技专项(LY807)。

摘　　要：采用质点运动判别法与偏振分析法相结合的方法,测定了四川九寨沟7.0级地震余震序列的S波分裂参数:快波偏振方向和慢波延迟时间,获得了6个台站S波分裂参数结果:位于余震密集区的L6202台有2个快波优势偏振方向(NNE向和近EW向),在主震后1个月其快波偏振方向为近EW向,随着余震的发生应力得到释放,其快波偏振方向调整为NNE向;L5111台无明显的快波优势偏振方向,体现了该区域复杂的地质结构和主震后应力调整作用;L5112台的快波优势方向为NNE向,与岷江断裂走向大体一致;位于余震密集区东侧的JZG台快波偏振方向为NW向,与塔藏断裂的走向一致;位于余震密集区南侧的L5110和L5113台的快波优势偏振方向为近EW向,与九寨沟区域应力场方向基本一致;各台站的归一化平均慢波延迟时间在1.2~5.0 ms/km范围内,L6202、L5112台的平均慢波延迟时间明显大于JZG、L5110台,反映出余震密集区的应力积累强于其他区域。This paper combination aspect ratio method and the polarization analysis method to measure the S-wave splitting parameters of MS7.0 earthquake sequence occurred in Jiuzhaigou area, Sichuan Province: polarization direction of fast S-wave and the delay time of slow S-wave of the earthquake sequence. Finally, we got the S-waves splitting results at 6 stations, the results show: there are two dominant polarization directions(NNE and EW) of fast Swave at stations L6202 in dense aftershock area. One month after the main-shock, with the stress release caused by aftershocks, the dominant polarization directions of fast S-waves at station L6202 adjusted from EW to NNE. Due to the complex geological structure of the area and the stress adjustment after the main shock, there is no obviously dominant polarization direction of fast shear waves at station L5111. The dominant polarization direction of fast Swaves is in NNE at station L5112, which is consistent with the strike of Minjiang fault. The dominant polarization direction of the fast S-waves is in NNE at station JZG, located in the eastern of the aftershocks dense area, which is consistent with the strike of Tazang fault. The dominant polarization directions of the fast S-waves are approximate EW, in agreement with the direction of the regional principal compressive stress, at stations L5110 and L5113 located in the southern of the aftershocks dense area. Furthermore, the time delay of slow S-wave is in the range of 1.2~5.0 ms/km. The time delay of slow S-wave at stations L6202 and L5112 is obviously more than at stations JZG, L5110,suggesting the stress accumulation in the dense aftershocks area is stronger than other area.

关 键 词：S波分裂 快波偏振方向 慢波延迟时间 

分 类 号：P315.31[天文地球—地震学]