【摘要】 采用有限元方法模拟了俯冲带耦合作用对巽他弧及其邻区的影响.根据模拟结果,对比GPS、地震和地质学观测数据,定量分析了苏门答腊及其周边地区的应变强度和主应变方向的分布特征,据此探讨了该区构造特征、地震发生模式与耦合面积之间的关系.模型由具有黏弹性性质的岩石圈和软流圈上地幔组成,其中岩石圈包括了大陆岩石圈和大洋岩石圈以及俯冲至上地幔中的俯冲板片.研究结果如下:(1)通过对不同俯冲带耦合面积模拟,发现苏门答腊前弧伴随耦合面积的增加应变强度逐渐增大,而增大的应变强度又影响了其周边地区的应变分布特征,因此整个苏门答腊前弧呈现出明显的分段性,这与该区地震破裂模式有较好的对应.(2)苏门答腊北部地区主应变方向与南部相比存在一定的差异,该差异是俯冲带的俯冲方向、俯冲速度、俯冲形态以及不同区域间耦合面积共同作用的结果.(3)虽然苏门答腊2004年地震主震区处于弱耦合状态,但从本文模拟的结果中可以看到,在俯冲作用下该区依然存在垂直向下的位移,这为地震激发海啸提供了有利的构造环境.更多还原

【Abstract】 The effect of subduction coupling zone on the Sunda fore-arc and its surrounding area is modeled using finite element analysis.Based on the simulation results,which are compared with GPS survey,seismological data and geological analysis,we quantitatively analyze the distribution of strain intensity and direction of principal strain of the Sumatra and its surrounding area.Then, the relationship between the area of subduction coupling zone and tectonic evolution is discussed accordingly.The model consists of lithosphere and upper mantle of athenosphere with viscoplasticity properties.The lithosphere includes the continental lithospheric,the oceanic lithospheric and subducted slabs.The results are as follows:(1) by adjusting the area of subduction coupling zone,we find out that with coupling area increasing,the value of strain intensity tends to increase.Meanwhile,the distribution of strain field in the other areas can be affected by increase of strain intensity.Therefore,the Sumatra fore-arc shows an obvious segmentation of strain intensity,which corresponds to the rupture pattern of the Sumatra earthquake belt.(2) There is a difference in principal direction of strain between the north and the south of Sumatra,which results from the integrated effects of various subduction velocity, direction,configuration and coupling area in different regions along the subduction zone.(3) Although the northern Sumatra is in a weak coupling condition based on our simulation results, there still exists a vertical negative displacement influenced by the subduction.This result shows that this area is a tectonic environment of the development of tsunami after earthquake.更多还原