Abstract: Located at the mid-section of the north-south seismic zone in China, the Minshan block was resulted from the reverse and over-thrust movement of the Minjiang fault and the Huya fault from west to east. Under the background of a regional main compressive stress field with NWW direction, the Minjiang fault shows an obvious reverse and overthrust movement with some sinistrogynic slip components, while the Minshan block has strongly uplifted since Quaternary. The aerial photo interpretation and field survery on geology and seismology indicate that the Mingjiang blook is composed of several secondary faults with echelon pattern, among them, the row distance of Gamisi Chuanpan dextral echelon part is 3 km, which perhaps controls the secondary seismic rupture unit. Research by the geological landform formation history and rupture landform shows that the average vertical slip rate of the Minjiang fault is 0.37～0.53 mm/a, the horizontal slip amount is similar to the vertical slip amount since late Quaternary, the average lift rate of Minshan Block is 1.5 mm/a since Quaternary. It is suggested that M≥6.0 earthquakes occurred mainly on the border faults of the strong blocks, while middle and small earthquakes often took place on the faults with nearly east-west direction and new tectonic lift, which are associated with the active features of these faults.

Key words: Active fault, Active block, Rupture landform, Seismicity

摘要： 岷山断块由岷江断裂和虎牙断裂自西向东的推覆逆掩运动所形成,处于我国南北地震带的中段。受区域NWW向主压应力场的控制,岷江断裂带第四纪以来表现为明显的推覆逆掩运动并具有一定的左旋走滑分量,岷山断块则处于强烈的隆起抬升状态。航片解译及野外地质考察结果表明,岷江断裂带由数条次级断裂呈羽列组合而成,其中尕米寺-川盘右阶羽列区的羽列距达3km,控制了低序次的地震破裂单元。第四纪地貌发育过程及断错地貌研究结果表明,岷江断裂晚第四纪以来的平均垂直滑动速率为0.37～0.53mm/a,水平位错量与垂直位错量大致相当;岷山断块第四纪以来的平均隆起速率为1.5mm/a左右。地震活动特征表明,该地区6级以上强震丛集于强烈活动的断块边界断裂上,中强地震及小震发生在新构造隆起区及近东西向断裂带上,与断裂的活动性质具有密切的成因联系。

关键词: 活动断裂, 活动断块, 断错地貌, 地震活动