南北地震带北段近期强震趋势研究

2008年5月12日汶川8.0级地震后,南北地震带可能进入新一轮的强震活跃期.从汶川8.0级地震以来ML≥5.0地震活动空间分布特征来看,近期南北地震带北段与中、南段存在较大差异.由南北地震带强震前孕震区中强地震活动特征,并结合当前5级地震活动情况,认为应同时关注南北地震带中、南段和北段的强震危险性.甘东南地区出现的4级地震空区被2011年2月23日迭部-岷县交界ML4.4地震打破后,2011年11月1日空区周边又发生了青川Ms5.4地震,表明该空区及周边地区的地震活动增强.类比1990年共和7.0级地震前的空区演化过程,认为甘东南地区存在发生7级地震的可能.结合对甘东南地区主要大型断裂7级地震复发周期的综合分析认为,需关注南北带北段毛毛山断裂和金强河断裂、香山-天景山断裂东段、黄河断裂灵武段、西秦岭北缘断裂、六盘山-宝鸡断裂和东昆仑断裂东段玛沁-玛曲段发生7级地震的可能.

Study of strong earthquake recent trends on the northern segment of north-south seismic belt

After the May 12, 2008 Wenehuan Ms8.0 earthquake, the north-south seismic belt has probably entered a new active period of strong earthquakes. The spatial distribution of ML5. 0 seismic activity since the Wenchuan Ms8.0 earthquake shows that the seismic activity has significant difference between the northern and the central-southern section of the north-south seismic zone recently. The characteristics of the strong earthquake activity in the seismogenic area before earthquake on the north-south seismic zone and the current condition of ML5.0 seismieity, draw our attention to the risk for strong earthquake both in the central-southern section and the northern section of north-south seismic zone. After the M4.0 seismic gap of the southeast Gansu was broken by the event which occurred in the junction of Diebu and Minxian on February 23, 2011, and Qingehuan Ms5.4 earthquake occurring around the seismic gap on November 1, 2011, it reveals the enhancement of seismic activity at the gap and its surrounding. The analog of the evolution of the seismic gap before the 1990 Gonghe M7.0 earthquake shows a possibility of a magnitude 7.0 in the southeast of Gansu. Combining with the M7.0 recurrence period of major large-scale fault, a comprehensive analysis shows that we should watch for the Maomaoshan fault and the Jinqianghe fault of the northern section of the north-south seismic zone, the eastern section of Xiangshan-Tianjingshan, the Lingwu segment of Yellow River fault, the north margin fault of West Qinling, Liupanshan-Baoji fault, the Maq~n-Maqu segment of eastern section of East Kunlun. There exist the possibility for the occurrence of a event with magnitude 7.0 along these faults.