芦山地震发震构造及余震震源机制
发布时间：2018-10-21 12:25
【摘要】：本文对2013年芦山Ms7.0级地震震中周边29个地震台记录到的震后一年多的微小余震进行了定位,并求取了震源机制。结果显示,芦山地震余震在平面上主要沿着双石-大川分支断裂及其周边分布,在垂向上主要集中在大约5-20km深度之间的两条交叉带上。其中一条余震带倾向北西,倾角在12km左右深度发生变化,浅部倾角较陡,该余震带延伸至地表与双石-大川分支断裂和新开店断裂之间的推测隐伏断裂位置相重合。另一条余震带倾向南东,该余震带延伸至地表的位置与双石-大川断裂非常接近,但与该断裂倾向相反。主震震源位置与两条余震带相交的位置接近,且芦山地震主震的两个节面产状与这两条余震带的深部几何形态正好对应,该结果表明芦山地震主震可能是两条余震带所对应的两条断裂同时活动的结果。芦山地震主震为南东向逆冲活动,但震后一年多的余震以正断和走滑活动为主。余震震源机制结果显示,主震发生后区域水平最大主应力方向由震前的NW向转变为震后的NNE向。这可能说明芦山地震使得震中区域应力释放比较彻底,并造成了区域构造应力场的较大变化。
[Abstract]:In this paper, the small aftershocks recorded by 29 stations around the epicenter of the 2013 Lushan Ms7.0 earthquake are located and the focal mechanism is obtained. The results show that the aftershocks of the Lushan earthquake are mainly distributed along the biste-Dachuan branch fault and its periphery on the plane, and in the vertical direction it is mainly concentrated in the two intersecting zones between the depth of 5-20km. One of the aftershock zones inclines to the north west, the dip angle changes at the depth of 12km and the shallow dip angle is steep. The aftershock zone extends to the ground surface and coincides with the location of the conjecture hidden fault between the bistale-Dachuan branch fault and the Xinkaidian fault. Another aftershock zone, which extends to the surface of the earth's surface, is very close to the bistale-Dachuan fault, but opposite to the fault. The location of the focal point of the main shock is close to the position of the intersection of the two aftershock zones, and the occurrence of the two nodes of the main shock of the Lushan earthquake coincides with the deep geometry of the two aftershock zones. The results indicate that the main shock of the Lushan earthquake may be the result of the simultaneous activity of two faults corresponding to two aftershock zones. The main shock of the Lushan earthquake is the south east thrust, but the aftershocks more than one year after the earthquake are mainly positive faults and strike-slip activities. The focal mechanism of the aftershock shows that the direction of the maximum horizontal principal stress in the region after the occurrence of the main shock changes from the NW direction before the earthquake to the NNE direction after the earthquake. This may indicate that the Lushan earthquake made the regional stress release completely and caused the great variation of the regional tectonic stress field.
【学位授予单位】：中国地质科学院
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P315
[Abstract]:In this paper, the small aftershocks recorded by 29 stations around the epicenter of the 2013 Lushan Ms7.0 earthquake are located and the focal mechanism is obtained. The results show that the aftershocks of the Lushan earthquake are mainly distributed along the biste-Dachuan branch fault and its periphery on the plane, and in the vertical direction it is mainly concentrated in the two intersecting zones between the depth of 5-20km. One of the aftershock zones inclines to the north west, the dip angle changes at the depth of 12km and the shallow dip angle is steep. The aftershock zone extends to the ground surface and coincides with the location of the conjecture hidden fault between the bistale-Dachuan branch fault and the Xinkaidian fault. Another aftershock zone, which extends to the surface of the earth's surface, is very close to the bistale-Dachuan fault, but opposite to the fault. The location of the focal point of the main shock is close to the position of the intersection of the two aftershock zones, and the occurrence of the two nodes of the main shock of the Lushan earthquake coincides with the deep geometry of the two aftershock zones. The results indicate that the main shock of the Lushan earthquake may be the result of the simultaneous activity of two faults corresponding to two aftershock zones. The main shock of the Lushan earthquake is the south east thrust, but the aftershocks more than one year after the earthquake are mainly positive faults and strike-slip activities. The focal mechanism of the aftershock shows that the direction of the maximum horizontal principal stress in the region after the occurrence of the main shock changes from the NW direction before the earthquake to the NNE direction after the earthquake. This may indicate that the Lushan earthquake made the regional stress release completely and caused the great variation of the regional tectonic stress field.
【学位授予单位】：中国地质科学院
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P315
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