乌鲁木齐市断层附近地应力特征与断层活动性

Characteristics of in-situ stress measurements near the fault and fault activity in Urumqi City

为了查明乌鲁木齐西山—碗窑沟断裂带地应力分布特征,在研究区20km×20km的范围内布置12个基岩应力钻孔,采用水压致裂地应力测量技术进行了基岩原地应力测量;共布置了2条观测剖面,第一剖面是沿断层走向布置了7个钻孔,第二剖面在垂直断层走向布置了6个钻孔(与第一剖面共用1个钻孔).根据实测的地应力资料,断层附近最大水平主压应力方向为NE—NEE向,与区域构造应力SN—NNE向主压方向有一些差异,说明受断层活动影响,断层附近的应力状态与区域应力场明显不同.利用地应力实测资料,研究了断层的活动性,在测量深度域内水平和垂直应力的关系为σH>σh>σv,该应力状态有利于逆断层活动,与地质资料反映的以逆断层活动为主基本一致.利用库仑摩擦滑动准则,摩擦系数取0.6～1.0分析,断层附近的现今地应力状态达到或超过产生逆断层摩擦滑动的临界值,表明测区现今构造应力有利于逆断层活动.

In order to determine the in-situ stress distribution around the Xishan-Wayaogou fault zone in Urumqi City. 12 boreholes for in-situ stress measurements were deployed in a 20 km ×20 km area to constitute two measurement profiles. One is along the fault strike with 7 boreholes, and the other is perpendicular to the fault with 6 boreholes, The in-situ stress measurements have been carried out in the boreholes using hydraulic fracturing technique. The results show that the direction of maximum horizontal principal stress near the fault is NE-- NEE, different with the direction of regional tectonic stress that is SN--NNE. It indicates that the direction of stress near the fault is obviously different from regional tectonic stress, implying the effect of fault activity. The horizontal stress value increases with depth with a relationship O＇H^0＂h^O＇v, a stress state favorable for activity of reverse faults, consistent to the geological data. According to Coulomb friction criteria and takingμ = 0.6 ～1.0, the stress state near the fault reaches or exceeds the critical value required for reverse faulting, indicating that the current tectonic stress is favorable to reverse faulting.