昆仑山M_S8.1地震震源参数的多破裂段模拟研究

A multi-segment analytic modeling of hypocentral geometric characteristic parameters of the M_S8.1 earthquake at the Kunlun Mountains

昆仑山MS8.1地震的已有研究结果在破裂带长度、破裂面方向、破裂面大小等震源破裂特征参数方面存在较大差异.本文采用D-InSAR技术首次获得昆仑山MS8.1地震干涉同震形变场,结合野外科学考察的实测值,进行了主破裂带InSAR视线向变化量的分解,通过对InSAR分解结果、野外科学考察、遥感解译等多源数据综合分析,重新划分了昆仑山地震的次级破裂段.进而通过对地震南北盘同震应变的分析,发现了昆仑山地震的南北两盘分别受挤压和拉张两种应力作用,研究表明多种岩石在拉张和压力作用下其最小主应力下的杨氏模量表现出非线性弹性特征,从而提出对昆仑山地震地表位移及震源特征参数分析时应考虑非线弹性介质导致的非线性弹性位移分布特征.基于上述原因,本文对Okada线弹性位错模型的算法进行了改进,提出了“多震源、非均一位错分量、多破裂段叠加”的线弹性模型,该模型模拟出的形变场干涉纹图较好地体现了地震形变场的分布特征,并由此获得了一套较为完整的地震发震断层的几何学特征参数,为破裂带长度、破裂面方向、破裂面大小等震源破裂特征参数研究提供了较好的解释.

We make a further study on the hypocentral parameters such as the length and width, the direction and the size of the rupture of the Ms8.1 earthquake at the Kunlun mountains. First, using D-InSAR technology, the co-seismic deformation field of the earthquake is obtained for the first time. Combining the field investigation data, along the main rupture zone the displacement in the satellite line of sight （LOS） is decomposed. Synthesizing the results of InSAR, field investigation and interruption by remote sensing images, the sub-rupture zone of the earthquake is mented again. Second, by analyzing the strain of north-south blocks of the fault, we find an asymmetric displacement distribution between the two sides of the rupture, and the two blocks are subject to compressional and tensional stress respectively. It is a pattern that cannot be explained with the linear elastic theory. However, laboratory experiments and in situ measurements in boreholes have shown that many crustal rocks exhibit a nonlinear elastic behavior in compression and tension with a dependence of the Yoting＇ s modulus on the minimum principal stress. So we suggest that the nonlinear displacement distribution should be considered when dislocation and hypocentral parameters are analyzed. Finally, we present an arithmetic of muhiple-hypocentral, heterogenous dislocation, and a multi-rupture segment superposition model for simulating the earthquake deformation field. The simulated LOS interferometry map presents the distribution characteristics of the earthquake deformation field better than that of previous studied. Meanwhile, a suit of fault geometric parameters of the earthquake is also obtained by the study. Having a better effect upon simulating asymmetry, great dislocation, macro rupture field, and non-hSmogeneity of dislocation than the traditional model, the multi-segment method is a progress of this work. it provides a better explanation for the study on hypocentral parameters.