乌鲁木齐九家湾断层组末端变形特征分析

ANALYSIS OF TERMINAL DEFORMATION CHARACTERISTICS ON JIUJIAWAN FAULTS IN URUMQI

九家湾断层组发育于九家湾中更新世砾石台地上,影像迹象清晰。断层向东西两侧年轻地貌面延伸,地表形迹不显著。根据九家湾断层组第二条(F_(2))延伸方向,在该断层西南延伸方向布设探槽,开挖并揭示出断层活动迹象,分析了九家湾断层组西末端的变形特征。探槽显示,断层末端仅有北倾正断层活动,断层带缩小成一条裂缝,垂直错距3~25 cm。断层上断点埋深1 m左右。表明九家湾断层西末端断层宽度、活动程度及变形程度均大幅度降低。本研究为断层末端相应地段地震危险性评价提供了有力的资料支撑。

Jiujiawan faults are located in Jiujiawan middle Pleistocene gravel terrace and the faults are very clear in the image.The fault extends to the young geomorphic surface on the East and west sides,and the surface trace is not significant.Based on the extending direction of the Jiujiawan faults(F_(2)),the trenches are excavated in the southwest and we find the active trace of fault.Moreover we analyze the west terminal deformation characteristic of Jiujiawan faults.The faul t’s terminal only grows up the main normal fault which dips north and the fault is nearly a fissure.The vertical offset is 3 to 25 centimeters.The fault lies hidden in the earth about 1 meter.It displays that the width,active degree and deformation range are all decreasing in Jiujiawan faults’west terminal.This study provides forceful materials with the seismic risk assessment on the faults’terminal related areas.