2011年9月10日瑞昌—阳新4.6级地震的震源破裂特征与区域强震危险性

基于区域数字地震台网记录,采用HYPODD方法精确定位了2011年9月10日瑞昌—阳新地震序列的震源位置,采用CAP方法反演得到了4.6级主震的震源深度和震源机制解,并结合区域深度震相sPg、PmP和sPmP对主震震源深度进行了进一步确定,随后探讨了这次地震的震源破裂特征和所在区域的强震危险性.结果显示:瑞昌—阳新4.6级地震的震源深度为15±2 km,震源机制解为节面Ⅰ走向30°,倾角86°,滑动角-169°,节面Ⅱ走向299°,倾角79°,滑动角-4°,发震构造为郯城—庐江断裂带往震区延伸隐伏的瑞昌—武穴断裂;本次地震发生在长江中下游断块东部,所在区域的5.5级以上地震具有明显的成组活动特征,近期显著地震集中发生在郯城—庐江断裂带南段及其分支断裂上,地震能量有加速释放的趋势,未来十年左右该区域存在发生6级左右强震的可能性.

Rupture characteristics of the Ms4.6 Ruichang-Yangxin earthquake of Sep.10, 2011 and the strong earthquake risk in the region

Based on the records of regional digital seismic networks, we relocated precisely the M_S4.6 Ruichang-Yangxin earthquake sequence of Sep. 10, 2011 with the HYPODD method, and obtained the focal depth and focal mechanism of the M_S4.6 main-shock with the "Cut and Paste" (CAP) method. In order to determine the focal depth, we combined with local depth phases like sPg, PmP, and sPmP to research it,and further discussed the rupture characteristics of the event and the strong earthquake risk in the region. Our result shows that the focal depth of the M_S4.6 Ruichang-Yangxin earthquake is 15±2 km and the best double couple solution is 30°, 86°, and -169° for strike, dip, and slip angles respectively with the other nodal plane of 299°, 79° and -4°. Combining with the rupture characteristics and the geologic settings in the region, we infer that the event is caused by the Ruichang-Wuxue fault which is the Tangcheng-Lujiang fault buried in the seismic zone.The Ruichang-Yangxin earthquake occurred in the east of the middle and lower Yangtze River fault-block,the M_S≥5.5 earthquakes in the region show the obvious features of seismic grouping activity, and the recent significant earthquakes mostly occurred on the Tangcheng-Lujiang fault or its adjacent fault, which shows the tendency of accelerating energy release. So we should pay more attention to the risk of about M6 earthquake in the region in the future years.