鲜水河断裂反“多”字型地裂缝带的成因机制

本文以1981年道孚6.9级地震考察资料为基础,结合1973年炉霍地震资料并运用光弹,泥料实验,讨论了鲜水河断裂上反“多”字型地裂缝带的成因机制。笔者认为反“多”字型地裂缝是断层水平剪切运动的产物,出现与相邻两条羽列裂缝交替部位的鼓包是裂缝水平错动在垂直方向调整作用的结果。鼓包两翼往往东陡西缓,鼓包轴部的逆断层也往往由西向东逆掩,这可能与断裂南西侧向南东运动有关,是以滇菱形断块向南南东运动产生的结果

ON THE MECHANISM OF THE FORMATION OF ANTI XI-TYPE (ξ-TYPE) GROUND CRACK ZONES ALONG THE XIANSHUIHE FAULT

The anti xi-type seismic zones can be found along the Xianshuihe fault as the form of ground fractures, most of them in the form of alternative tensile-shear cracks with the compressional drumlins or the thrust. And the drumlins may usually appear in the gaps where the cracks run en echelion.On the basis of the field observations of the Daofu (M = 6.9) earthquake of 1981 and the information of the Luhuo (M = 7.9) earthquake of 1973, this paper discussed the mechanism of formation of the ground crack zones in terms of photoelastic experiment on clay.The author inclined to consider the studied ground crack zones to be the result of strik-slip movement along the Xianshuihe fault and the drumlins in the gaps between en echelon cracks were generated due to resulting adjustment in the normal direction at both terminals of the cracks from their lateral displacement. According to the shape of the drumlins and thrusting direction the author came to a preliminary conclusion that this kind of ground crack zones can be accounted for by the SSE-trending movement of the Sichuan Yunnan rhombic fault block