西秦岭北缘断裂和海原断裂的走滑转换变形及其与陇山地块的相互作用

NEW EVIDENCE OF ACTIVITY OF XIANNUSHAN AND TIANYANGPING FAULT ZONE IN LAST PERIOD OF LATE-PLEISTOCENE

根据对调查资料、航卫片判译和已有文献的综合分析，研究了西秦岭北缘断裂（ＸＱＬＦ）东段和海原断裂（ＨＹＦ）南段的走滑转换、变形及其与陇山地块的相互作用。ＸＱＬＦ以几何学结构复杂和多期活动为特征，主带各段呈左阶斜列。ＨＹＦ南段的陇县－宝鸡断裂（ＬＢＦ）由４条断层组成７０ｋｍ的宽带，中更新世以来表现为左旋走滑运动。ＸＱＬＦ和ＬＢＦ在运动过程中均产生走滑挤压或走滑拉伸的转换变形。被上述断裂切割围限的陇山地块，从晚白垩世至早第四纪一直处于强烈的挤压变形状态。中晚第四纪以来，可能还具有顺时针旋转变形和位移。

Based on mapping geological sections of the Xiannushan and the Tianyangping fault zones with the feild trial trench, new evidence of palaeoearthquake activity of two fault zones in last period of Late-Pleistocene are found by studing the accumulation and tectonite of fault zones, deformations of new-old tetonites, mechanism and geometry of dislocation and age determination of filling soil-rock in the fault zones and others. It is shown that two or four medium strong earthquakes occurred between 18200±1200 and 16900±760 years in the south branch of Tianyangping fault zone, and four medium strong earthquekes between 29000±1300 and 10000 years (probable) in the middle segment of Xiannushan fault zone.