伸展盆地构造演化的数值模拟——以南海北部白云凹陷为例

介绍了瞬时均匀拉伸模型、挠曲悬臂梁模型和多幕伸展模型，特别强调各种模型的基本假设和适用条件，以及基于这些模型发展出的二维正反演模拟和一维应变速率模拟的方法。这些方法在计算岩石圈伸展系数和盆地张裂的过程中，具有一定的优越性。在盆地的数值模拟中，有时需要综合运用多种数值模型来突破单个模型假设条件的约束。为了研究南海北部白云凹陷的裂后沉降特点，分别应用二维正反演和一维应变速率正反演方法计算岩石圈的伸展系数，并计算理论热沉降，与实测裂后沉降进行对比。模拟结果表明，白云凹陷岩石圈的伸展系数大致呈钟形分布，在凹陷中心处最大，大约为3.5；凹陷的实测裂后沉降远大于理论值，即存在裂后异常沉降，裂后期的异常沉降总量在凹陷中心和南部在2km以上。

Numerical modeling of the tectonic evolution of extensional basin: take Baiyun sag of northern South China Sea for example

This paper introduced the models of instantaneous uniform stretching, flexural cantilever stretching, and multiphase stretching, with special emphasis placed on their basic assumptions and application conditions. 2D inverse and forward modeling and 1D strain rate modeling have strong superiority on studying the lithospheric stretching factor and rifting process. In the numerical modeling, we often need to combine some models together in order to break through the limitation of the assumptions that existed in each single model, for example, using the flexural cantilever model and multiphase stretching model together to simulate the multi-rifting process. With the purpose of researching the post-rift subsidence characteristics of the Baiyun sag, we use the 2D inverse and forward modeling and 1D strain rate modeling to calculate the lithospheric stretching factor and theoretical thermal subsidence, comparing with the observed post-rift subsidence. The distribution of the lithospheric stretching factor is shaped like a bell, with the maximum value 3.5 in the center of the sag. The observed post-rift subsidence is much bigger than the theoretical post-rift subsidence in the center and south of the sag, with the anomalous post-rift subsidence over 2km.