塔里木盆地雅克拉断凸古构造应力场数值模拟

Numerical simulation of palaeotectonic stress field in Yakela faulted salient,the Tarim Basin

雅克拉断凸长期处于挤压环境,逆断层发育,但在喜马拉雅早期正断层也发育。为了研究雅克拉断凸的断层发育特征,对海西晚期和喜马拉雅早期古构造应力场进行三维有限元数值模拟。结果表明,海西晚期整个研究区在挤压应力作用下皆为中、低应力值区,中、东部南侧是低应力值区,往北、往西应力值增加,该应力场导致研究区内部发育了一些规模较小的逆断层。喜马拉雅早期研究区在挤压应力作用下向上隆起,隆起幅度由西向东逐渐增加,隆起导致地层弯曲,且以边界断裂顶部附近区域弯曲度最大,导致此处的拉张应力也最大,正断层正是从此处开始发育,然后再向内发展;与此同时,研究区下部受到的挤压应力作用较小,导致内部的逆断层几乎没有进一步发育。

Thrust faults are widely developed in Yakela faulted salient due to long-term compression regime. However, some normal faults were also formed during the Early Himalayanian. In order to decode the mechanism of formation and evolution of these faults, we conducted 3 D finite element numerical simulation for the Late Hercynian and Early Himala- yan stress field in the Yakela faulted salient. During the Late Hercynian, the compressive stress resulted in the low stress areas in the central and eastern parts of the Yakela faulted salient and the low to moderate stress in the west and north part. This stress field caused the development of some small-scale thrust faults in the Yakela faulted salient. During the Early Himalayan, the compressive stress induced uplifting of the study area, with the amplitude of uplifting increasing from west to east. As a result, the strata bended in the study area, with the strongest tensile stress occurring on top of the boundary fault, and normal faults were also developed in these locations and extended inwards. Meanwhile, compression stress was weak in the lower part of the whole study area, thus did not induce the further development of thrust faults in the inner parts of the study area.