四川省北川县活动断裂的地质响应

The Geological Response of Active Fault in Beichuan County,Sichuan Province

【目的】探讨北川县不同区域对断裂活动的地质响应机制。【方法】从岩层年龄、岩石类型、岩层产状、滑坡点密度、地貌高程等角度分析断裂上、下盘差异活动对北川县不同地区地质特征的影响。【结果】断裂上盘岩石类型相对单一,主要发育以千枚岩为主的变质岩,断裂下盘岩石类型复杂,各类沉积岩广泛分布;相对于下盘区域,断裂上盘地势高峻、地表出露岩层更古老、岩层倾角更大、滑坡点密度更高;另外,以北川-映秀断裂为界,上、下盘区域均表现出岩层年龄值与岩层距断裂距离值成反比的特征。【结论】总体来看,龙门山地区构造应力强度的区域差异及北川-映秀断裂的逆断层性质导致了北川县不同区域对断裂活动产生不同的地质响应方式。

[Purposes]Investigate the geological response mechanism of active fault in Beichuan County.[Methods]The effect of differential activity of the hanging wall and foot wall to geological characteristics in different regions of Beichuan county was analyzed from the perspective of digenetic age,rocks type,attitude of rocks,the density of landslide sites,geomorphology.[Findings]The main rock type is simple on the hanging wall of the fault;the phyllites are mainly developed in the region.The rock types are complicated on the foot wall;the various kinds of sedimentary rocks are widely distributed.Compared with the geological response modes on the foot wall,the elevation is higher and dating of rock is older and strata inclination is larger and the density of landslide sites is bigger on the hanging wall of the fault.In addition,the dating of rock is inversely proportional to the distance between strata and fault on the hanging wall and foot wall of Beichuan-Yingxiu fault.[Conclusions]As a whole,the different geological response modes of active fault was produced in different regions of Beichuan county because of the regional difference of stress intensity in Longmen Mountain and reverse fault property of Beichuan-Yingxiu fault.