【摘要】：本文對2013年蘆山Ms7.0級地震震中周邊29個地震臺記錄到的震后一年多的微小余震進行了定位,并求取了震源機制。結果顯示,蘆山地震余震在平面上主要沿著雙石-大川分支斷裂及其周邊分布,在垂向上主要集中在大約5-20km深度之間的兩條交叉帶上。其中一條余震帶傾向北西,傾角在12km左右深度發(fā)生變化,淺部傾角較陡,該余震帶延伸至地表與雙石-大川分支斷裂和新開店斷裂之間的推測隱伏斷裂位置相重合。另一條余震帶傾向南東,該余震帶延伸至地表的位置與雙石-大川斷裂非常接近,但與該斷裂傾向相反。主震震源位置與兩條余震帶相交的位置接近,且蘆山地震主震的兩個節(jié)面產狀與這兩條余震帶的深部幾何形態(tài)正好對應,該結果表明蘆山地震主震可能是兩條余震帶所對應的兩條斷裂同時活動的結果。蘆山地震主震為南東向逆沖活動,但震后一年多的余震以正斷和走滑活動為主。余震震源機制結果顯示,主震發(fā)生后區(qū)域水平最大主應力方向由震前的NW向轉變?yōu)檎鸷蟮腘NE向。這可能說明蘆山地震使得震中區(qū)域應力釋放比較徹底,并造成了區(qū)域構造應力場的較大變化。
[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.
【學位授予單位】：中國地質科學院
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P315

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