基于流体动力学数值模拟的海水层反射地震研究

摘要

Computational fluid dynamics(CFD)and seismic forward modeling are used to study marine seismic reflection facies.Meso-scale ocean dynamic study based on marine seismic reflection data interpretation is a new trend in seismic oceanography(SO).While ocean dynamics are observed in marine seismic data,they are affected by rough morphology and coexisting sea water motion,which are too complex to explain using traditional seismic interpretation methods.To solve this problem,a new method that combines CFD and SO is proposed in this work.First,CFD is employed using MITgcm(MIT General Circulation Model)to generate a series of temperature sections.Then,seismic forward modeling is applied to temperature sections to simulate marine seismic data,according the physical meaning of a numerical simulation profile with observed SO data.Finally,forward modeling results are compared with observed SO data.Matching with observed seismic data of shoaling internal solitary waves(ISW)propagating westward in the northeastern South China Sea(SCS),three snapshots of CFD temperature sections reveal seismic reflection event features of depression,fission and transition ISW.CFD and seismic forward modeling,when combined with proper background flow and initial model,permit to reveal complex water-column seismic reflection facies and predict the evolution of meso-scale ocean dynamics.%由于多种海水运动同时存在以及地形的影响,海水层结构非常复杂,解释海水层地震相,分析海水运动过程是地震海洋学研究的新方向.本文提出结合流体动力学数值模拟与反射地震正演分析海水层地震相的方法.首先,对地形和流体建模,得到特定条件下流体运动状态;然后用反射地震正演将模拟获得的海水层温盐剖面转换为反射地震数据;进一步和实际测量得到的地震海洋学剖面进行对比,分析地形、海水运动对海水层地震相的影响.以内孤立波浅化过程为例,通过流体动力学数值模拟,获得其浅化过程中出现的下沉型、分裂、转换型三个阶段的海水层剖面;对温盐剖面进行反射地震正演,分析浅化不同阶段海水层反射几何形态、反射结构等特征.这种新方法有望解释复杂地震海洋学图像,深化海底地形对海水运动影响的认识.