用面积平衡原理预测伸展断陷盆地中岩层内部应变及亚分辨正断层的方法

Analysis Method for Predicting Strain of Interior Beds and Sub-Resolution Faults from Area-Balance Theory in Extensional Basin

大多数地堑和半地堑是由深度近水平的拆离正断层控制的 .根据面积平衡原理 ,这些伸展断陷盆地岩层的区域基准面至拆离断层面高度 (h)与其损失面积 (S)呈线性比例 .拆离断层之上的盆地基底岩层的水平伸展量相同 ,因此 ,用“S -h图解法”可以确定拆离断层深度 ,并能在此基础上计算出岩层的总水平伸展量 .伸展盆地中的总水平伸展量主要是由不同尺度的正断层的水平离距体现出来的 .可观测解释的断层的水平位移可以通过测量盆地宽度、岩层长度等直接得到 .用剖面面积平衡方法可计算出盆地各岩层的平行岩层面的应变 ,其中相当部分是由在观测尺度上不能直接解释出来的“亚分辨正断层”的小尺度位移造成的 .因此 ,在分析伸展断陷盆地的构造样式、岩层力学性质基础上 ,有可能对计算得到的平行岩层的伸展应变进行合理评估 ,进而可以定量地预测“亚分辨正断层”的密度和可能的分布部位 .

Extensional basin includes mainly graben and half-graben controlled by low detachment. Based on the area-balance theory, there is a linear equation between a height of regional to detachment (A) on the outside of the basin and lose area (S) of the regional in extensional basin. The basement beds above detachment are of same extensional displacement so that 'S-h diagram' can be used to determine the depth to detachment and to calculate the total extensional displacement of the beds above detachment. The extensional displacement is dominated by the heave of various scale normal faults. The displacement of obvious faults can be immediately figured out by measured bed-length. The requisite displacement calculated by area balance is the layer-parallel strain, which could be the extensional displacement of sub-resolution faults. Accordingly, the layer-parallel strain can help us to predict the magnitude and distribution of .sub-resolution fault on the base of analysis of structural style and rheological behaviour.