三角剪切断层传播褶皱作用理论与应用

Theory and application of tri-shear fault propagation folding

基底断层在沉积盖层中传播所形成的褶皱形态难以用平行膝折褶皱理论进行解释,这在于两者的流变学性质有很大差异。Erslev提出了三角剪切断层传播褶皱理论,认为下伏断层的脆性强破裂变形为向上变宽的三角形分布式剪切所调节,三角形顶点固定于断层端点。Hardy和Ford拓展了这一理论并成功地建立数字模拟模型,Allmendinger进一步建立与完善了三角剪切的正演模型与反演方法。通过运动学模型预测结果与天然构造观察和相似模拟实验结果的对比分析,以及通过一系列力学模型对运动学模型的检验,三角剪切断层传播褶皱理论被证实并获得了广泛应用。对前陆盆地、克拉通盆地和走滑盆地的基底卷入型构造与走滑或斜向滑动构造,都可以应用三角剪切断层传播褶皱理论来分析变形样式及其分布特征。该理论可以有效地预测隐伏断层的初始破裂点、断层传播量与发育部位,已成功地应用于工程地质与地震灾害预报等方面。

The fold geometry formed by propagation of basement fault into sedimentary cover is quite difficult to explain based on parallel folding theory owing to the marked rheological difference between the basement and the sedimentary cover. Erslev put forward a theory called the tri-shear fault propagation folding, which holds that the strong brittle deformation of underlying fault is accommodated by a triangular-like widening-upward distributional shear zone, and the triangle apex is pinned to the fault tip. Hardy and Ford put forward a mathematical method to model its evolution. Allmendinger succeeded in establishing the forward- and the inverse modeling method of tri-shear folding based on Hardy and Ford＇s models. According to the comparison among the prediction by the kinematic models and the observation of natural structures and the results of analogous experiment, as well as a series of tests of mechanical models on the kinematic models, the tri-shear fault propagation folding has been proved and got a wide range of application. It can be used in the analyses of the deformation styles and the deformation distribution of the basement-involved or the strike-slip or the oblique-slip structures such as in the foreland basins, in the cratonic basins, or in the strike-slip basins. It can also be employed to predict effectively the blind fault nucleation point, the fault propagation amount, and its occurring stratigraphic intervals. Thus it has been applied successfully in such areas as engineering geology or forecasting of the earthquake.