基于深地震反射剖面大炮数据的频率域全波形成像方法研究

The frequency-domain inverse imaging method of seismic wave equation, comparing with time-domain imaging method, has advantages of flexible data selection, avoiding numerical error accumulation, and easy parallel computation. It can make great use of the extractable information from the seismogram, including body wave, surface wave travel time and waveform information, so that the compatibility of the model and the overall fitting of the theoretical waveform to the data can be improved to provide more details of lithospheric structure. However, low computational efficiency, excessive dependence of imaging results on the initial model, and high requirements on seismic data quality restrict the development and application of such method. For above problem, this study firstly improve the efficiency of frequency-domain full waveform imaging, according to constructing high-precision numerical schemes for discretizing frequency-domain wave equations; proposing a preconditioned Krylov subspace method based on a detailed analysis on the mathematical structure and properties of the coefficient matrix of linear system after the discretization; combining proper optimization method, a high-efficiency frequency-domain full waveform imaging algorithm can be obtained and used to Sanjiang area, Yunnan province. Based on high signal-noise ratio reflection seismic profiling big-shot data, we perform high-resolution imaging for this lithospheric structure of this area to deepen the understanding of lithospheric structure, and provide critical seismological evidence for the deep dynamic background and lithospheric morphology of the lateral collision mineralization belt in the Qinghai-Tibet Plateau.

地震波动方程频率域成像方法，相比于时间域成像方法，具有数据选择灵活、能避免误差累积、易于并行等优点。它能最大程度地利用地震记录中可提取的体波、面波走时和波形等信息，从而可提高模型的兼容性及理论波形对数据的整体拟合精度，提供更多岩石圈结构的细节。然而计算效率偏低、成像结果过度依赖初始模型、对地震数据质量要求较高等问题制约着该方法的发展和应用。针对以上问题，本项目首先开展提高频率域全波形成像计算效率的研究，即通过构造高精度数值方法离散波动方程，详细分析离散后所得线性方程组的数学结构与性质，并提出快速求解的预处理Krylov子空间方法，结合适当的优化算法，发展一套高效的频率域全波形成像方法。在此基础上，将其应用于云南三江地区，通过采用高信噪比的反射地震大炮数据对该区域进行地下高分辨率成像，深化对研究区岩石圈精细结构的认识，为青藏高原侧向碰撞成矿带的深部动力学背景和岩石圈形态提供关键的地震学证据。