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地震断层几何形态的确定是研究断层震源破裂过程和地面运动的先决条件.其中断层的破裂深度和倾角是两个未知的关键参数.半无限空间的地震弹性位错理论公式表明,除纯走滑断层以外,对于断层破裂至地表的地震产生的地表变形,其上盘水平应变的零值点与破裂深度之间存在简单的对应关系,可由地表的零应变点直接推算断层深度.本文通过数值计算方法探讨了盲断层与非均匀介质情形下,利用地表零应变点推算断层破裂深度的可行性.结果显示,介质和应力场的非均匀性一定程度上影响了对应关系;对于盲断层,当埋深在~1 km以内时,对应关系近似成立.此外,根据地表水平变形还可估算断层倾角的范围.最后探讨了如何根据大地震后的孔径雷达干涉方法记录推算断层破裂深度的方法,并将此方法应用于2008年汶川大地震,获得了这次地震的断层破裂深度.这种利用地表变形观测确定断层几何参数的方法简便易行,没有余震的影响,可以为反演提供有价值的约束.
The determination of seismic fault geometry is a prerequisite for the study of the fault rupture process and ground motion, in which the fault rupture depth and dip angle are two unknown key parameters.The seismic elastic dislocation theoretical formula in the semi-infinite space shows that except the pure strike slip Besides the faults, there is a simple correspondence between the zero-point and the rupture depth of the horizontal strain of the upper plate for the surface deformation caused by earthquakes ruptured from the fault to the earth’s surface, and the fault depth can be directly calculated from the zero strain point of the earth’s surface.Through numerical calculation The method is used to estimate the fault rupture depth in the case of blind faults and inhomogeneous media. The results show that the heterogeneity of the medium and the stress field affects the corresponding relations to some extent. For the blind faults, The corresponding relation is approximately established when the depth is within 1 km, and the range of fault dip angle can be estimated according to the horizontal deformation of the ground surface.Finally, how to record the estimated depth of fault rupture according to the method of aperture radar interference after a large earthquake is discussed. This method was applied to the Wenchuan Earthquake in 2008 and obtained the fault rupture depth of this earthquake. Table deformation observation method to determine the geometric parameters of the fault simple and easy, without aftershocks, can provide valuable constraints for the inversion.