贵州东南部榕江加里东褶皱带内的现今地应力分布特征及构造分析

贵州东南部位于盖层极不发育的榕江加里东褶皱带内，为查明该区域内的地应力状态，在贵州省黔南州境内进行了7个钻孔的水压致裂地应力测量工作，同时结合贵州西部已有研究结果和贵州西北部1个钻孔的地应力测量资料，对贵州东南部与西部和西北部的地应力分布差异进行了对比研究，最后结合断层的活动性质以及Byerlee准则探讨了测孔区域断层的稳定性，结果表明:水平主应力在研究区占主导地位，最大水平主应力方向表现为北西向；根据安德森断层理论，三向主应力的相对大小有利于逆断层和走滑断层的活动，这与研究区发育的活动断层性质相对应；最大和最小水平主应力的线性拟合结果表明，研究区水平主应力的梯度大于黔西煤层地区、广西盆地东北部和全国的地应力梯度值，最大水平主应力的值在相近深度上大于黔西、黔西北地区和广西盆地东北部；三都断裂带附近存在较高的构造应力，μ_m值（最大剪应力与平均主应力的比值）较高，表明断层处于摩擦极限平衡状态；而三江-融安断裂两侧的构造作用存在较为明显的差异，西侧的构造作用强于东侧；虽然部分钻孔内的μ_m值都处于高值，但区域应力方向与断层多以较大角度相交，因此断层是稳定的，这与研究区的地震活动性相吻合。 

DISTRIBUTION OF PRESENT-DAY CRUSTAL STRESS AND TECTONIC ANALYSIS IN THE RONGJIANG CALEDONIAN FOLD BELT, SOUTHEASTERN GUIZHOU

Southeastern Guizhou is located in the Rongjiang Caledonian fold belt, which is very undeveloped in caprock. In order to find out the state of crustal stress in this area, the hydraulic fracturing stress measurements of 7 boreholes were carried out. A comparative study was made on the distribution differences of crustal stress in the southeast, west and northwest of southeastern Guizhou, combining with the research results of west Guizhou and crustal measurement data of a borehole in northwestern Guizhou. Finally the fault stability around the sampling borehole area was discussed in association with fault activities and the Byerlee criterion. The results demonstrate that the horizontal principle stress is dominant in the study area, and the maximum horizontal principal stress is in the N-W direction; according to the Anderson fault theory, the relative magnitude of the three-direction principal stress is favorable to the movement of the thrust fault and strike-slip fault, which corresponds to the nature of the active fault developed in the study area; the linear fitting results of the maximum and minimum horizontal principal stresses show that the gradient of horizontal principal stress is larger than that of the coal seam area in western Guizhou, the northeastern Guangxi basin and the whole country, and the maximum horizontal principal stress is larger than that of western Guizhou, northwesternern Guizhou and the northeastern Guangxi basin at the similar depth; there are high tectonic stresses near the Sandu fault zone, and the μ_m value (the ratio of the maximum shear stress to the average principal stress) is higher, which indicates that the fault is in the state of friction limit equilibrium; the tectonic action on both sides of the Sanjiang-Rongan fault is obviously different, and the tectonic action on the west side is stronger than that on the east side; although μ_m values are high in some boreholes, the direction of regional stresses intersect with the fault at a larger angle, so the fault is stable, which is consistent with the seismicity in the study area.