大同震区地震序列震源位置及震源区速度结构初探

Study on Earthquake Sequence Location and Velocity Structure in Datong Hypocenter Area

采用震源位置和速度结构联合反演的方法对大同震区1989年6.1级、1991年5.8级、1999年5.6级3次地震地震序列进行了震源位置和震源区速度结构反演,以确定3次地震序列的分布和震源区的速度结构。结果表明：3次地震序列的发震断裂为NNE向的大王村断裂和NWW向的团堡断裂,两条断裂表现为交替发震;3次地震序列的震源深度平均为10.06 km,其中以6~15 km为发震优势层;研究区速度结构与大的地貌特征相符,沿大同盆地第四纪沉积层表现的不间断低速带,从大同县一直延伸到阳高、天镇等地。在中部山自皂台附近出现了一高速区位置与大同火山群分布区相近。大同—阳高3次地震序列分布在相对高速区上,表明这一区域为应力集中地区。

Using the epicenter location and velocity structure joint inversion method,the earthquake location and velocity structure inversion of the 1989 M6.1,1991 M5.8 and 1999 M5.6 earthquake sequences in Datong area has been carried out to determine their earthquake sequence distribution and hypocenter area velocity structure.The results indicate that：（1） the seismogenic faults are Dawang fault with NNE strike and Tuanbo fault with NWW strike for the three earthquake sequences,and the three earthquake sequences occurred alternately at the two faults;（2） the average epicenter depths of the three earthquake sequences all are 10.06 km,and 6～15 km is the dominate seismogenic layer;（3） the velocity structure of the study area is consistent with the large geomorphologic feature,behaving as uninterruppted low-velocity belt along the Quaternary sediments in Datong basin from Datong extending to Yanggao and Tianzhen.One high-velocity area appears at Shanzizao seismological station in the middle basin,which location is close to the Datong volcanic cluster area.Datong-yanggao three earthquake sequences distribute in the relatively high velocity area,indicating that this area is a stress concentration area.