渭河断裂杨家村—窑店段展布及晚第四纪活动特征

DISTRIBUTION OF YANGJIA VILLAGE-YAODIAN SECTION OF WEIHE FAULT AND THE CHARACTERISTICS OF ITS LATE QUATERNARY ACTIVITY

渭河断裂杨家村—窑店段西起杨家村,经魏家泉、金家庄、东耳村、陈家台,到达窑店,走向NE,倾向S,长约33km,为同生正断层,沿渭河北岸I级、Ⅱ级、Ⅲ级阶地前、后缘展布。遥感解译、浅层地震探测、探槽、钻孔联合剖面结果表明,渭河断裂杨家村—窑店段在咸阳附近的渭河北岸阶地表现为断层陡坎,与NE向阶地坎重合;断裂在晚更新世晚期至全新世可能仍有活动。渭河断裂杨家村—窑店段自（46.0±3.3）ka以来断距较大,在11.0~16.5m之间;垂直滑动速率在0.34～0.45mm/a之间;断裂最新活动时间约为2.0ka BP。金家庄左阶斜裂区将渭河断裂杨家村—窑店段划分为杨家村—金家庄段和东耳村—窑店段。

The Yangjia Village-Yaodian segment of Weihe Fault,starting from Yangjia Village in the west,passing through Weijiaquan,Jinjiazhuang,Donger Village,Chenjiatai to Yaodian,occurs as a NEstriking fault dipping south with a total length of 33 kilometers. As a syn-depositional normal fault,it extends along the leading and trail edge of T1,T2 and T3terrace at the northern bank of Weihe River.Results of remote sensing interpretation,shallow seismic exploration,exploratory trench,and drilling show that the Yangjia Village-Yaodian section of Weihe Fault manifests as fault scarps,overlapping with the NE-extending terrace scarp at the northern bank of Weihe River. Weihe Fault broke the T1 that can be distinguished on the shallow seismic profile and multiple profiles with broken signs from T1 to the ground,which is the same with the cracks through the Han Tomb at the top of the exploratory trench in Yangjia Village. It shows that the fault may still be active from the late Pleistocene to Holocene. Through composite drilling section and the analysis of exploratory trench,there is no significant difference in activity between the Yangjia Village-Jinjiazhuang and Donger Village-Yaodian section. This segment has experienced a large displacement event since（ 46.0±3.3） ka BP,approximately 11.0～16.5m,with a vertical slip rate of 0.34～0.45 mm / a. The most recent activity occurred approximately around 2.0ka BP. The left-step en echelon fracture zone at Jingjiazhuang separates this section into two minor ones,Yangjia Village-Jinjiazhuang section and Donger Villag-Yaodian section. Yangjia Village-Yaodian section in Weihe Fault and YaodianZhangjiawan section which was found out in the Xi＇ an active fault detection and seismic risk assessment project can be combined into the Yangjia Village-Zhangjiawan section.