陇县—岐山—马召断裂几何结构特征

陇县—岐山—马召断裂是陇县—宝鸡断裂带中规模最大、 活动性最强的一支, 其几何特征与晚第四纪活动性对认识鄂尔多斯块体西南缘的地震构造特征与构造变形模式具有重要意义。 在对高分二号卫星遥感影像解译(空间分辨率0.8 m)和1∶50000 DEM分析的基础上, 结合野外地质调查, 确定断裂的几何展布。 陇县—岐山—马召断裂整体走向为300°~315°, 西北起于草碧镇, 向东南经千阳、 岐山、 扶风南部一线的黄土台塬, 经哑柏镇抵于秦岭北马召镇, 全长约130 km。 断裂晚更新世以来整体表现出左旋走滑为主的运动特征, 在部分段落具一定垂直运动分量。 根据断裂的阶区、 断裂交会和分离、 断裂晚第四纪活动性等特征将陇县—岐山—马召断裂分为三段, 自西北向东南依次为草碧—田家沟段、 底寺—古水段和绛帐—马召段。 其中, 草碧—田家沟段又可细分为左阶排列的两个次级段, 即草碧—沙坳段与枣子沟—田家沟段。 陇县—岐山—马召断裂在岐山县北与北山山前断裂交会, 为草碧—田家沟段和底寺—古水段的一个分段标志, 陇县—岐山—马召断裂与北山山前断裂交会后有3 km行迹模糊。 陇县—岐山—马召断裂在古水村与渭河断裂交会, 为底寺—古水段和绛帐—马召段的分段标志, 绛帐—马召段以与秦岭北缘断裂交会为标志分段。

Segmentary Characteristics of the Geometrical Structure of the Longxian—Qishan—Mazhao Active Fault

The Longxian—Qishan—Mazhao fault is the largest and most active one in the Longxian—Baoji fault zone. The characteristics of its Late Quaternary tectonic activity and geometrical structure are of great significance for understanding the seismic deformation and tectonic deformation pattern of the southwestern margin of the Ordos block. In this study,based on the interpretation of high-resolution satellite remote sensing images and analysis of DEM(1: 50000), combined with fieldwork, geometric distribution of the fault was determined. Longxian—Qishan—Mazhao fault strikes 300 °~315 °, starting from Caobi town, passing through Qianyang County, Qishan County, fault scarp of the Loess Plateau in the southwestern of Fufeng County, Yabai town to Mazhao town in the north of Qinling piedmont, extending about 130 km. Since the Late Pleistocene, the whole movement of left-lateral strike-slip has been characterized, and normal component has been found in some segments. According to the segmentary signs of strike-slip faults, such as the fracture zone, fault intersection, and separation, Longxian—Qishan—Mazhao fault was divided into three segments. From northwest to southeast, there are Caobi—Tianjiagou segment, Disi—Gushui segment and Jiangzhang—Mazhao segment respectively. Caobi—Tianjiagou segment can be divided into two left stepped form sub-segments, which are Caobi—Sha'ao segment and Zaozigou—Tianjiagou segment. Longxian—Qishan—Mazhao fault intersects with the Beishan fault at the north of Qishan county, which can be taken as an indicator of segmentation of Caobi—Tianjiagou segment and Disi—Gushui segment. There is a 3 km loss of fracture in this area. Longxian—Qishan—Mazhao fault intersects with the Weihe fault at the Gushui village, which can be taken as an indicator of segmentation of Disi—Gushui segment and Jiangzhang—Mazhao segment. Jiangzhang—Mazhao segment intersects with north piedmont of Qinling fault is a sign of segmentation.