中国断裂构造体系的发展

根据岩石和模拟实验的结果,应力在超过屈服强度以后,试样的表面常出现小鼓包,而且体积也有所膨胀。这一现象与所谓“扩容”(dilatancy)相当,主要是由于内部结构在应力作用下发生松弛(relaxation)并产生微裂隙(Microfissuring)的结果,因此出现应力降,相当大地震前微震,并表现为其他前兆现象。它们也常表现为粒内滑动以及双晶等微观现象。

ON THE DEVELOPMENTS OF FRACTURE-SYSTEMS IN CHINA

According experiments on fracture-development in both rocks and clay-models, wrinkles appear usually on the surfaces of these samples when the applied stress exceeds their yielding strength. Such a phenomenon may be considered to be equivalent to the so-called dilatancy. With further increase of stresses on the samples there appear obviously X-shaped microshear-fractures conjugated each other in pairs, roughly net-like with long axis of rhombs and acute angles pointing in the direction of com-pressive stress. Under still further increasing stresses, zig-zag fractures of tension usually develop by adapting each other to the already formed X-shaped shear-planes alternatively.Fracture-systems are the groups of fractures developed due to unified stress-field acting at the same time, under the same boundary condition of the same lithological character. They may tentatively be classified into:1. X-shaped shear fracture system2. Y-shaped shear-tension fracture system3. I-shaped tensile fracture systemFractures may also preliminarily be classified also into five types as follows according to the depth they penetrate as well as their geological and geophysical indications :1. Lithospheric fractures2. Crustal fractures3. Foundational fractures4. Superficial fractures5. Layer-gliding fracturesThe X-shaped conjugated fractures or lineaments show themselves not only in China, but also all over the earth. Besides, their (outward) appearances on the moon and Mars are not seldom.