三峡库首区现今构造应力场的形成体制分析

ANALYSIS OF THE FORMATION SYSTEM OF THE PRESENT TECTONIC STRESS FIELD IN THE HEAD AREA OF THE THREE GORGES RESERVOIR

本文从地质、地震、形变、地应力测量等方面对三峡库首区现今构造应力场进行了系统的分析和论证,并用数值模拟进行了验证,认为三峡库首区现今构造应力场属于纯剪切变形体制,即:在来自西部NE—SW方向主压应力挤压的基础上,同时叠加有因江汉—洞庭盆地拉张而引起的NWW—SEE向主张应力的作用,这两种力源近于直交,可以分别作为研究区现今构造应力场的主压应力(1σ)和主张应力(σ3)。

The present tectonic stress field in the head area of the Three Gorges reservoir was systematically analyzed and verified in the geological, seismological, deformation and in situ stress contexts and checked by numerical modeling. The authors think that the present tectonic stress field in the study area belongs to a pure shear system, i. e. the superimposition of the NE-SW principal compressional stress from the west is superimposed by the WNW-ESE principal tensional stress resulting from extension of the Jianghan-Dongting basin. The axes of the two stresses intersect nearly perpendicularly to each other; so they can act as the principal compressive stress （σ1） and the principal tensional stress （σ3） of present tectonic stress field in the study area respectively.