Kang Seung-Goo, Jang U Geun
Division of Earth Sciences, Korea Polar Research Institute, Incheon 21990, Republic of Korea.
Department of Geological Sciences, Chungnam National University, Daejeon 34134, Republic of Korea.
Sensors (Basel). 2023 Jul 23;23(14):6622. doi: 10.3390/s23146622.
Seismic oceanography can provide a two- or three-dimensional view of the water column thermocline structure at a vertical and horizontal resolution from the multi-channel seismic dataset. Several seismic imaging methods and techniques for seismic oceanography have been presented in previous research. In this study, we suggest a new formulation of the frequency-domain reverse-time migration method for seismic oceanography based on the analytic Green's function. For imaging thermocline structures in the water column from the seismic data, our proposed seismic reverse-time migration method uses the analytic Green's function for numerically calculating the forward- and backward-modeled wavefield rather than the wave propagation modeling in the conventional algorithm. The frequency-domain reverse-time migration with analytic Green's function does not require significant computational memory, resources, or a multifrontal direct solver to calculate the migration seismic images as like conventional reverse-time migration. The analytic Green's function in our reverse-time method makes it possible to provide a high-resolution seismic water column image with a meter-scale grid size, consisting of full-band frequency components for a modest cost and in a low-memory environment for computation. Our method was applied to multi-channel seismic data acquired in the Arctic Ocean and successfully constructed water column seismic images containing the oceanographic reflections caused by thermocline structures of the water mass. From the numerical test, we note that the oceanographic reflections of the migrated seismic images reflected the distribution of Arctic waters in a shallow depth and showed good correspondence with the anomalies of measured temperatures and calculated reflection coefficients from each XCDT profile. Our proposed method has been verified for field data application and accuracy of imaging performance.
地震海洋学可以从多道地震数据集中，以垂直和水平分辨率提供水柱温跃层结构的二维或三维视图。先前的研究中已经提出了几种用于地震海洋学的地震成像方法和技术。在本研究中，我们基于解析格林函数，提出了一种用于地震海洋学的频域逆时偏移方法的新公式。为了从地震数据中成像水柱中的温跃层结构，我们提出的地震逆时偏移方法使用解析格林函数来数值计算正演和逆演波场，而不是传统算法中的波传播建模。与传统逆时偏移不同，基于解析格林函数的频域逆时偏移不需要大量的计算内存、资源或多波前直接求解器来计算偏移地震图像。我们逆时方法中的解析格林函数使得能够以米级网格尺寸提供高分辨率的地震水柱图像，该图像由全频段频率分量组成，计算成本适中且在低内存环境下进行。我们的方法应用于在北冰洋采集的多道地震数据，并成功构建了包含水体温跃层结构引起的海洋学反射的水柱地震图像。通过数值测试，我们注意到偏移地震图像的海洋学反射反映了浅深度北极水域的分布，并且与每个XCDT剖面的实测温度异常和计算反射系数显示出良好的对应关系。我们提出的方法已在现场数据应用和成像性能准确性方面得到验证。
