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1973年2月6日,四川省甘孜藏族自治州炉霍县发生了7.9级强烈地震,震中烈度为10度,通过震中区沿鲜水河谷产生了长达90公里的地震裂缝带。裂缝以张扭性的为主,伴有少量压性和扭性结构面,其组合型式有反“多”字型、斜列式、锯齿状和棋盘格式等四种,反映的运动方式以水平运动为主,最大水平错距达3.6米,垂直落差都在20—30厘米。本文着重研究了这次地震所产生的各种类型地裂缝的力学特征,结合地质构造背景探讨了地震区应力作用方式及地震成因。从地震裂缝带出现的位置、力学性质、活动方式与鲜水河断裂相一致来看,这次地震是鲜水河断裂的最新活动,是该断裂运动的必然结果。
On February 6, 1973, a magnitude 7.9 earthquake hit Luhuo County, Ganzi Tibetan Autonomous Prefecture, Sichuan Province. The epicenter intensity was 10 degrees, producing a seismic fracture zone of up to 90 kilometers along the Xianghui River valley through the epicenter area. The cracks are mainly torsional, accompanied by a small amount of compressive and torsional structural surfaces. There are four types of combinations, such as anti-“multi”, oblique, jagged and checkerboard formats, Sports, the largest horizontal gap of 3.6 meters, the vertical drop in the 20-30 cm. In this paper, the mechanical characteristics of various types of ground fissures produced by this earthquake are studied emphatically. Based on the geological tectonic setting, the stress modes and the causes of earthquakes are discussed. Seen from the position, mechanical property and activity mode of the seismic fracture zone coinciding with the Xianshuihe fault, this earthquake is the latest activity of the Xianshuihe fault and is the inevitable result of the fault movement.