【摘要】 2014年8月3日,云南省昭通一鲁甸地区发生M_s6.5级地震,造成了重大的人员伤亡和财产损失.鲁甸震区位于扬子块体的西缘,小江断裂带的东侧北东向的昭通—莲峰断裂带内.由于至今没有穿越该断裂带的人工源深地震测深剖面,而丽江—攀枝花—清镇650 km长深地震测深剖面距离鲁甸主震区不超过50 km,利用宽角地震资料的初至波震相,通过有限差分反演揭示该地区上地壳速度结构,可以为鲁甸震区的地震定位、地震孕育机制等提供深部速度模型.速度剖面显示:剖面结晶基底厚度平均为2 km左右;小江断裂带速度较低,东西两侧的速度较高;因此小江断裂带区域地壳强度比较低,加上断裂两侧的应变速率很高,所以小江断裂带和旁边的鲁甸—昭通断裂带,未来具有发生较大地震的可能,值得关注.更多还原

【Abstract】 On August 3,2014,an M_s 6.5 earthquake occurred in Ludian County,Yunnan.The Ludian earthquake ruptured along the NE-orie.nted Zhaotong-Lianfeng fault zone,western margin of the Yangtze block.However,there was no seismic sounding profile across the Zhaotong—Lianfeng fault zone up to now.Since the distance from Lijiang—Panzhihua—Qingzhen active source seismic sounding profile to the Ludian earthquake source region is within50 km,we can handle the wide-angle seismic data to reveal the upper crustal velocity structure in this area,and provide the velocity model of upper crust for the earthquake locating and focal mechanism inversion of Ludian earthquake sequence,etc.The velocity profile shows that the crustal velocity around the Xiaojiang fault is lower than its periphery,thus the rheological strength of the upper crust beneath the Xiaojiang fault is speculated to be weaker than its surrounding areas.Considering the high strain rate along the Xiaojiang fault,it is possible to accumulate great strain and strong stress in the Xiaojiang fault zone and its surrounding faults.Thus we should pay attention to the potential risk of strong earthquakes on the Xiaojiang fault and its nearby Ludian—Zhaotong fault.更多还原