南北地震带北段近期强震趋势研究

摘要

After the May 12, 2008 Wenchuan 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 seismicity, 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 MA. 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 Qingchuan 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 Maqen-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.%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.