汶川地震震中映秀地区地表破裂特征

Characteristics of the Surface Rupture of the M_S8.0 Wenchuan Earthquake on the Epicenter,Yingxiu Area

汶川8级大震的震中位于映秀镇,地震在映秀地区造成了多处地表破裂,如公路拱曲、地震陡坎,坡中槽新变形等,长度达300余米。经实地全站仪和GPS测量,定量分析了地表破裂的垂直分量与水平分量以及两者之间的比值,以此揭示了映秀—北川断裂的运动性质为逆冲兼右行走滑,在映秀地区逆冲分量大于走滑分量。将本次地震造成的位错数据与震前资料对比,发现汶川地震产生的地表破裂位置与地质历史上映秀—北川断裂造成的断层位错位置是相当吻合的,说明映秀地区Ⅳ级阶地上40余米的的断层陡坎可能是地质历史时期若干次大地震的结果。

On the epicenter area of Wenchuan great earthquake in 2008, Yingxiu town, Sichuan province, the earthquake caused a number of surface rupture, such as road bending deformation, fault scarps and new deformation at ＂the groove in the slope＂, the total length of zone is about 300 meters. Using total station and GPS, at 4 rupture points the displacement were measured, and the vertical and level components of offset were analyzed quantitatively, as well as the ratio between them. The result shows that the motion of seismogenic Yingxiu--Beichuan fault is mainly thrust with some right-lateral strike slip, the thrust component is greater than the strike-slip component at Yingxiu area. Comparing the surface rupture before and after the event at same place, it is revealed that the earthquake rupture is anastomose with the active location of Yingxiu --Beichuan fault during recent geology history, which means that the fault scarp about 40 m on the terrace Ⅳ of Mingjiang river maybe is the results of number of major earthquakes in geological history.