全拖曳式深海直流电阻率法三维任意各向异性正演模拟

高精度、高效率的深海勘探是当前国家海洋资源勘探开发的研究热点之一，设计观测效率高、勘探成本低的探测方式，开发可精确计算海底复杂电性环境的正演模拟算法有助于推进该研究的进展。本文基于前人的研究经验，引入了全拖曳式深海直流电阻率观测方式，同时考虑到海底沉积环境的电各向异性，开发了基于非结构有限元方法的三维任意各向异性深海直流电阻率正演算法，实现了对海底任意电各向异性情况的仿真模拟。本文算法与层状一维模型半解析解的对比验证了算法的精度。对典型各向异性电性模型的仿真模拟和分析，证明了全拖曳式深海探测方式对海底沉积层和矿产资源电各向异性的高分辨率。在此基础上，总结了电导率各向异性主轴沿笛卡尔坐标旋转时视电阻率分布也发生同方向旋转的视电阻率分布特征，并根据海底地形对各向异性探测的影响进行了简单探讨。

3-D Arbitrarily Anisotropic Modeling for Towed Marine DC Resistivity Method in Deep Ocean

Deep-sea exploration with high precision is one of the research focuses in marine exploration. The traditional exploration by using a towed transmitter in seawater while positioning receiver at seafloor has the defects that the receivers can easily get lost, the data are instable, and the survey electrodes are influenced by ocean topography. In order to solve these problems, we designed an exploration technique with high working efficiency,reliability and low exploration cost, and developed a 3D DC forward modelling algorithm for accurately recognizing the electric characteristics of the sediment and mineral sources. Based on the previous researches, we put forwarded a towed marine DC resistivity method, and presented a 3D anisotropic forward modelling algorithm for deep-sea DC resistivity method by using finite-elements on unstructured grids for a fully towed DC system with considering the anisotropy of sea sediments at the ocean bottom. We checked the accuracy of our algorithm against 1D semi-analytical solutions for an arbitrarily anisotropic sea bottom. Through the numerical experiment analyses on typical anisotropic models, we demonstrated the high resolution of DC resistivity to the anisotropy of seafloor sediments and minerals. Based on these simulations, we summarized the characteristics of the apparent resistivity when the axis of the anisotropic conductivity rotted around the Descartes coordinate axis, and discussed the influence of the submarine topography on the anisotropic explorations.