安阳及邻区三维地壳速度结构研究

3-D crustal velocity structure in the An Yang and its adjacent regions

应用区域地震台网1985～2008年的地震到时资料,对安阳及邻区地壳三维速度结构和震源参数进行了联合反演,获得了该区地壳的三维速度结构图像.成像结果表明:研究区浅部地形速度分布特征为:凹陷盆地速度较低,山脉位于速度的过渡区,隆起区多位于高速区,速度横向分布差异较大;上、中地壳速度横向分布存在非均匀性,与区域构造分布特征存在着一定的联系;下地壳中、上部的速度分布表现为东部平原区域速度较高,西部太行山隆起区速度较低.区内断裂展布与速度横向变化较大地区有着较好的对应,多条断裂走向与高低速过渡带一致,断裂两侧速度存在明显差异;不同位置的深度剖面显示地震分布多位于速度横向分布不均匀处,同时与邻近断裂的分布也有着较好的对应关系.成像结果反映出深部构造的重要信息,为进一步研究该区的活动构造及地震参数计算,提供了科学依据.

The 3-D velocity tomography image of the Anyang and its adjacent regions is obtained by the joint inversion of 3-D velocity structure and focal parameters using the earthquakes recorded by the local seismic network between 1985 and 2008. The imaging results show that velocity distribution characteristics in the shallow terrain of the study area is： The velocity of down warped basin is relatively low, mountains are in the velocity transition zone, the uplift area is located in the high velocity zone, large difference is in lateral velocity distribution. There exists obvious lateral inhomogeneity in the up-middle crust, which has some contact with regional tectonic distribution characteristics. The velocity distribution in the up-middle section of the lower crust exhibits high velocity in eastern plain, while Taihang uplift in western shows low. The spread of faults corresponds to the area with large lateral velocity variation. The trend of multiple fault zone is consistent with the high-low velocity transition zone, while there are significant velocity differences in both sides of the fracture zone. The depth profiles in different locations indicate that earthquakes are mainly located in the area where lateral velocity distributes unevenly. At the same time, it also has a good corresponding relation to the distribution of the nearby fracture. The inversed velocity structure does primarily reflect some important features of the deep structure in the region and provides the scientific basis for the further study of active tectonic structure and the calculation of earthquake parameters.