渤海湾盆地裂后期快速沉降机制的构造-热演化模拟研究

渤海湾盆地是华北克拉通最大的新生代裂陷盆地及重要的含油气盆地，也是地震活动频繁的地区。其裂后期的构造沉降速率自上新世以来显著增加，与传统的指数衰减模型明显相悖，且伴随强烈的构造再活动。目前学术界对该盆地裂后期快速沉降的成因机制争议很大，证据之间的冲突也多存在。厘清盆地裂后期与热沉降无关的异常沉降量，并对可能的动力学模式进行建模、检验，可为剖析盆地裂后期快速沉降机制提供直接证据。本项目拟采用多幕非瞬时拉张模型计算盆地裂陷期的拉张系数及其后的热沉降量，确定异常构造沉降的起始时间及分布规律；在此基础上，对造成裂后期异常沉降的可能机制（拉张、挤压引起的岩石圈下挠、深部热异常）进行构造-热演化模拟；依据各模式在盆地热历史、现今热状态及Moho面深度等方面的不同响应，结合已有观测资料，分析其可能性。研究成果对完整认识渤海湾盆地新生代演化的动力学过程、油气成藏机理及地震动力学都具有重要的理论和应用价值。

The Bohai Bay Basin is the largest Cenozoic rifted basin of the North China Craton and an important petroliferous basin with active seismicity. The post-rift tectonic subsidence rate of the basin has significantly increased since the Pliocene, which is obviously inconsistent with the traditional exponential decay model. The basin had also experienced intensive tectonic reactivation during the post-rift stage. However, the mechanism of the rapid post-rift subsidence is still controversial, and conflicts among evidence exist. It can provide direct evidence for the mechanism of the rapid post-rift subsidence through clarifying the anomalous tectonic subsidence independent of thermal decay, and testing the possible geodynamic models. This project intends to firstly simulate the syn-rift stretching factor and the post-rift thermal subsidence using a multi-phase extension model, and determine the starting time and distribution of the anomalous tectonic subsidence. Then, we plan to conduct tectono-thermal modeling of the possible mechanisms accounting for the anomalous tectonic subsidence, including the rifting, compression-induced downwarping and deep thermal anomaly models. These models can be tested through comparing the calculated basin thermal history, present-day thermal state and Moho depth with those obtained from previous studies. The research results would have significant theoretical and practical value for understanding the complete geodynamic process of basin evolution through the Cenozoic, the mechanism of hydrocarbon accumulation and the dynamics of earthquake in the Bohai Bay Basin.