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1974年5月11日,在云南省昭通地区发生了7.1级地震。震中区位于金沙江下游南岸的山地中。 本文中,作者分析了震区大地测量资料,根据破裂与应变的关系,确立这次地震震源破裂属于逆冲型。依据烈度衰减和余震分布特征建立了矩形滑动断层模式参数,并应用曼辛哈(Mansinha)和斯迈利(smylie)给出的倾斜、有限滑动断层位移场的精确解析表达式,求得平均倾向滑距。结果是:断层走向N6°W,倾向N84°E,倾角60°,断面长20公里,宽30公里;断面顶部距地表深度2.5公里;平均倾向滑距2.8米,地震矩5.4×10~(26)达因·厘米;应力降51巴;释放的应变能下限1.2×10~(23)尔格。 作者还扼要地讨论了P波节面解和这次地震发生的构造条件,并解释了一些宏观地震现象。
On May 11, 1974, a magnitude 7.1 earthquake occurred in Zhaotong, Yunnan Province. The epicenter area is located in the mountains on the south bank of the lower reaches of the Jinsha River. In this paper, the author analyzed the geodetic data of the earthquake area and established that the earthquake source rupture belongs to the thrust type according to the relationship between rupture and strain. Based on the characteristics of intensity attenuation and aftershock distribution, the parameters of rectangular slip fault model are established and the exact analytical expressions of tilt and finite slip fault displacement field given by Mansinha and smylie are applied to obtain the average tendency Skidding. The result is: the fault strike is N6 ° W, the trend is N84 ° E, the dip angle is 60 °, the section length is 20 km and the width is 30 km; the top of the section is 2.5 km away from the ground surface; ) Dyne cm; stress drop 51 bar; release of the lower limit of strain energy 1.2 × 10 ~ (23) Erg. The authors also briefly discussed the P-nodal solutions and the tectonic conditions of the earthquake, and explained some macro-seismic phenomena.