Geometrical Form of Fault Zones in the Crustal Interior in Xichang Region Determined by Seismic Travel-time Tomography
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摘要: 断裂深部产状和空间几何关系是研究地壳运动变形、动力作用及其地表响应的基础,也是模拟发震断裂与强震关系的基础。为了研究川西南地区强震活动与安宁河、则木河和金河断裂的关系,对盐源-西昌-雷波高分辨地震折射剖面初至Pg波走时和断层面反射波走时进行模拟,获得了川滇活动地块东边界带安宁河、则木河和金河断裂的深部形态。结果表明:在上地壳内,安宁河断裂和则木河断裂东倾32°~35°,其速度结构为舌状低速带,二者规模较大,延伸到了基底。金河断裂东倾约30°,向下延伸至少5km。Abstract: The geometry of the fault and spatial relations between faults are the basis for studying the crustal deformation,dynamics,their surface response,and for modeling the relations between fault movement and strong earthquake.To fully understand the relation between strong earthquake and deep crustal faults,Anninghe fault,Zemuhe fault and Jinhe fault,we apply the algorithms on seismic ray tracing and travel-time modeling to first arrival Pg wave and reflection wave from the fault for Yanyuan-Xichang-Leibo high-resolution seismic profile,and the direct information on the velocity and fault from three faults mentioned above has been obtained.The results show that: Anninghe fault and Zemuhe fault incline towards east with dip of 32~35 degree,and their velocity structures present low velocity zone of tongue-like shape;those two faults extend downwards to the crystalline basement at large scale and control most strong earthquake activities in this region.Jinhe fault inclines towards east with dip of 30 degree,and extends downwards at least 5 km.
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