三向受压状态下地壳岩体的张性变形和张性破裂

本文叙述了处于三向受压状态的地壳岩体产生张性变形和张性破裂的原理,并以珠江三角洲地区为例说明:①岩体内应力集中点的浅部,可产生张性变形和张性破裂;②地质考察所观察到的张性或张剪性断裂,其断裂面上作用的正应力未必是拉应力,极有可能是压应力,但却一定是拉应变;③张性破裂引起的地震,震级较小,一般在4.5级以下,④地震引起的张性地裂缝的走向,就是震源应力场的主压应力方向。

TENSILE DEFORMATION AND TENSILEFRACTURE OF CRUSTAL ROCKS UNDERTRI-LATERAL COMPRESSION

In this paper, the principles of tensile deformation and tensile fracture of crustal rock under tri-lateral comres-sion are described, the Pearl River delta area is taken as an example to illustrate: 1) Tensile deformation and tensile fracture can take place along the direction of principal compressive stress at their stress concentration site in the shallow part of crustal rock bodies; 2) For the tensile or shearing faults observed in geological survey, the positive stress applied upon the fault plane may not necessarily be a tensile stress but very likely be a compressive stress, while the strain must be tensional; 3) The earthquake caused by tensile fracture is of lower magnitude, usually lower than M = 4.5; 4) The orientation of the tensile ground fissures resulted from an earthquake is possibly the direction of principal compressive stress of the stress field on the seismic source.