琼东南盆地地壳伸展因子计算及其伸展模式探讨

Estimation of the Stretching Factors of the Qiongdongnan Basin and Domino-Style Fault Model

对伸展因子β的计算分析,可认识岩石圈的伸展变形特点。基于琼东南盆地具有"多米诺"伸展断层构造的5条反射地震剖面资料,利用"多米诺"伸展断层模式计算了上地壳伸展因子,其值分布在1.17～1.58之间;与对应位置的全地壳和岩石圈的伸展因子比较,结果显示上地壳、全地壳和岩石圈伸展因子三者之间存在差别,但不是简单的随深度增大,具体表现为盆地中北部的岩石圈伸展变形特点为岩石圈伸展因子大于全地壳大于上地壳,盆地西南部则表现为全地壳最大,岩石圈最小。通过计算,结合研究区相关研究成果,本文认为琼东南盆地岩石圈发生了随深度变化的伸展变形;不同构造位置的岩石圈伸展变形存在明显差异。

The calculation of stretching factors provides a feasible method to understand the extension and thinning of lithosphere. Based on the seismic profiles of the Qiongdongnan basin, the upper crust stretching factors are estimated by applying the domino-style fault block model, with results ranging from 1. 17 to 1.58. The whole crust stretching factors and lithosphere stretching factors are also examined on the domino-style faults positions. The results demonstrate that there exists depth related difference, hut not simply increase with depth, which indicates a heterogeneous lithospheric stretching. In conclusion, the depth dependent model is likely operational in the Qiongdongnan basin.