新疆北天山西段构造应力场分析

ANALYSIS OF TECTONIC STRESS FIELD ON THE WEST PART OF NORTH TIANSHAN IN XINJIANG

利用地表构造形迹、地震震源机制解、现代水系展布的优势方向以及激光全息光弹模拟等综合分析方法,研究了北天山西段(东经82°～86°)地壳构造应力场的基本特征。指出,该区构造应力场的主压应力方向为近南北向。通过激光全息光弹实验获得模型的等差线及等和线条纹图,从而求解各点的主张应力σ_1主压应力σ_2和最大剪应力τ_max的相对值并绘制相应的等值线图,结果发现:实验区σ_1值普遍偏低,σ_2值明显偏大,说明本区处于整体受压状态。τ_max值的分布较均匀,仅在一些断裂的交汇部位和端点剪应力值较高。分析结果认为:萨尔萨拉西南、独山子——安集海断裂西端、乌苏林场西南、阿尔夏特一带、婆罗科努达坂东南都是围压很高的剪应力集中区。这些地区易积累大量的应变能而产生突发式剪切破裂和粘滑引起强烈地震,是在地震预报中值得注意的地震危险地段。

The main characteristics of crustal tectonic stress field on west part of North Tianshan(82°-86° East Long. )was studied by using comprehensive methods on surface structure shape,focal mechanism solution, superior orientation of contemporary water system and larger holographic photoelastic modelling. It is pointed out that the principal compressive stress direction of tectonic stress field in the area is nearly S - N. According to the low principal tensile stress and greater principal compressive stress, entirely compressional state in the area was appeared. The maximum shear stress Tmax was well distributed, and the higher Tmax value was located only at the cross place or both ends of faults. It is considered that the southwestern part of Sharshala, the west of Dushanzi - Anjihai fault, the southeastern part of Wusu Tree Farm,Alxiate and the southeastern part of Polokelu passage-way are the areas of shear stress concentration under the action of high surrounding pressure,and possible seismic risk districts as well.