丽江7.0级地震震源环境及其破裂过程讨论
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摘要
本文通过对丽江Ｍｓ７０地震发生环境和破裂过程的分析讨论，得到以下认识：丽江地震发生在滇西北裂陷区北部块体内，这是一个由三组深断裂切割包围的三角形断块，断块内发育有裂陷盆地（大具—丽江裂陷盆地）；该区除了水平应力作用外，还有很强的来自地幔物质上隆引起的垂直应力作用；主余震分布在地壳一个由相对低速区包围的高速区内。地壳介质结构横向非均匀性—地壳高速块体的存在，可能是丽江地震震源成核的重要成因。丽江７０级主震是一个单侧破裂过程，其过程非常复杂。主震为二次破裂事件，第一次破裂的中心位于大具，方向北北西，第二次破裂的中心位于黑水，方向转为北北东；整个破裂过程则从北向南沿着雪山东麓裂陷带的破裂，余震活动空段则显示了破裂过程的高度非均匀性
In this paper, through analysis and discussion on the seismogenic environment and rupture process of the Ms 7 0 Lijiang earthquake,the preliminary knowledge is obtained as follows:First,the Lijiang earthquake occurred in the north block of northwest Yunnan subside zone which is a triangle block cut and surrounded by the three deep faults, where the subside basin (Daju-Lijiang subside basin) develops, besides the action of horizontal stress,there exists the strong vertical stress caused by mantle uplift in this region,the mainshock and aftershocks are distributed in the high velocity zone in crust surrounded by relatively low velocity zones.Second, the lateral inhomogeneity of crust medium structure and existence of high velocity block in crust may be important genesis of the source nucleation of the Lijiang event.Last,the M 7 0 Lijiang earthquake is a complex unilateral rupture process.The mainshock is consisted of two rupture events; the center of the first rupture is located in Daju,with the directive in NNW and the center of the second rupture in Heishui with the direction in NNE; whole rupture process occurred along the fault in the easten foot of Snow mountain from north to south and the gaps of the aftershock activity display high inhomogeneity of the rupture process.
In this paper, through analysis and discussion on the seismogenic environment and rupture process of the Ms 7 0 Lijiang earthquake,the preliminary knowledge is obtained as follows:First,the Lijiang earthquake occurred in the north block of northwest Yunnan subside zone which is a triangle block cut and surrounded by the three deep faults, where the subside basin (Daju-Lijiang subside basin) develops, besides the action of horizontal stress,there exists the strong vertical stress caused by mantle uplift in this region,the mainshock and aftershocks are distributed in the high velocity zone in crust surrounded by relatively low velocity zones.Second, the lateral inhomogeneity of crust medium structure and existence of high velocity block in crust may be important genesis of the source nucleation of the Lijiang event.Last,the M 7 0 Lijiang earthquake is a complex unilateral rupture process.The mainshock is consisted of two rupture events; the center of the first rupture is located in Daju,with the directive in NNW and the center of the second rupture in Heishui with the direction in NNE; whole rupture process occurred along the fault in the easten foot of Snow mountain from north to south and the gaps of the aftershock activity display high inhomogeneity of the rupture process.
引文
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