2016年10月20日射阳MS4.4地震的震源机制与地震序列的时空分布特征

Focal mechanism of the Sheyang MS4.4 earthquake on October 20, 2016 and the spatio-temporal distribution of the earthquake sequence

  • 摘要: 基于江苏地区测震台网记录,采用CAP方法反演了2016年10月20日射阳MS4.4地震的震源机制解和震源深度;利用HypoDD方法对射阳地震序列中ML≥1.5地震进行了重新定位.结果显示:射阳MS4.4地震的震源机制参数分别为节面Ⅰ:走向304°,倾角53°,滑动角0°;节面Ⅱ:走向214°,倾角90°,滑动角143°,震源深度约为14 km.双差定位结果显示:此次射阳地震序列分布于洪泽—沟墩断裂与盐城—南洋岸断裂之间,在水平空间内,其震中分布的优势方向为NW60°,由SE向NW迁移; 地震序列深度分布在6—23 km范围内.根据所反演的震源机制参数和地震序列精定位结果,本文推测射阳MS4.4地震的断层面解为震源机制解的节面Ⅰ, 该地震可能是在区域背景应力场的作用下,沿NW向剪切破裂产生的左旋走滑地震事件.

     

    Abstract: Based on the digital waveforms of Jiangsu seismic network, the focal mechanism of the Sheyang MS4.4 earthquake was determined by using the CAP (cut and paste) method, and the ML≥1.5 events of Sheyang earthquake sequence were relocated by using the HypoDD method. The result shows that the strike, dip and rake of the MS4.4 event are 304°, 53°, 0° for the nodal plane Ⅰ, and 214°, 90°, 143° for the nodal plane Ⅱ, respectively, and the centroid depth is about 14 km. The relocation for the Sheyang earthquake sequence shows that the earthquake sequence was located between Hongze-Goudun fault and Yancheng-Nanyang'an fault with the predominant direction NW60° in horizontal space, and the sequence propagated from southeast to northwest with the focal depth of 6--23 km. According to the focal mechanism solutions and the relocation results, we deduce that the Sheyang MS4.4 earthquake is a left-lateral slip event induced by shear rupture northwestwards under regional stress field, and its fault plane is nodal plane Ⅰ.

     

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