新疆皮山地区地震动衰减关系研究

The study on strong ground motion attenuation relationship in the Pishan area,Xinjiang

摘要:

利用2015年7月3日皮山M_S6.5地震序列的波形资料，采用微遗传算法反演得到震源区的5个介质参数，即应力降Δσ为75.95bars，品质因子Q₀为186.33，η值为0.26，几何衰减分段点R₁为72.18km，R₂为139.70km；并由此计算得到的傅氏谱再配合随机相位谱，进而得到地震动时程，建立了震源区地震动衰减关系。由于缺乏强震记录，本文还收集了2008年10月5日乌恰M_S6.9地震、2008年10月6日阿克陶M_S6.2地震、2012年3月9日洛浦M_S6.0地震的强震数据，将计算结果与经验性衰减关系以及3次强震记录进行比较后发现，皮山地震、洛浦地震的强震数据普遍高于经验性衰减关系，乌恰地震的强震数据与俞言祥等文中的衰减关系吻合较好，在远场低于本文的计算结果。

Abstract:

Small earthquake data from the Pishan M_S6.5 aftershocks are collected by the Xinjiang Regional Digital Seismic Observation Network. Five parameters of the focal region are obtained by micro genetic inversion:stress drop of 75.95bars,quality factor parameters Q₀ of 186.33 and η of 0.26,geometric attenuation parameters R₁ of 72.18km and R₂ of 139.70km. We calculate the Fourier spectrum and combine with random phase spectrum to get the ground motion time history,and build the strong motion acceleration attenuation relationship. The strong ground motion acceleration attenuation of Pishan area is obtained. Because of the lack of strong ground motion records,we join the records of Wuqia earthquake on October 5,2008,the Aketao earthquake on October 6,2008 and the Lop earthquake on March 9,2012. The comparison of the calculation results and the empirical attenuation relationships with strong ground motion records reveals that the strong motion data of Pishan and Lop earthquake are higher than the empirical attenuation relationships. The Wuqia earthquake strong motion data are consistent with Yu Yanxiang(2013) short axis result,and lower than the present result.