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

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 σHσhσv,a stress state favorable for activity of reverse faults,consistent to the geological data.According to Coulomb friction criteria and taking μ=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.