Abstract
Fast Marching Method (FMM) boasts high calculation efficiency and strong adaptability and stability while being applied to seismic traveltime. However, when it is applied to the largescale model, the calculation precision of FMM is insufficient. FMM has poor calculation precision near the source, which is an essential reason for the low accuracy of the whole algorithm. This paper puts forward a joint traveltime calculation method to address the problem. Wavefront Construction (WFC) with a relatively high calculation accuracy rather than FMM is adopted for calculation of the grid nodes’ traveltime near the source. After that, FMM is used to calculate the seismic traveltime in the remaining area. Joint traveltime calculation method greatly improves the calculation accuracy of the source’s surrounding area and the calculation accuracy of FMM. According to the new method, FMM is still adopted for the calculation of most grid nodes in the model, so the high calculation efficiency of FMM is maintained. Multiple numerical models are utilized to verify the above conclusions in the paper.
Highlights
As the difficulty of finding oil and gas resources in shallow seismic exploration increases, in-depth seismic exploration is gaining more and more attention (Liang et al, 2016)
Based on the characteristics of the two traveltime calculation methods, this paper puts forward a joint traveltime calculation method based on the two calculation methods
Fast Marching Method (FMM) boasts high stability and efficiency while calculating the seismic traveltime, but the calculation accuracy near the source is low, which might influence the accuracy of the whole calculation method
Summary
As the difficulty of finding oil and gas resources in shallow seismic exploration increases, in-depth seismic exploration is gaining more and more attention (Liang et al, 2016). Traveltime calculation methods can mainly be divided into three kinds, including ray-based methods, finite difference methods, and new ray tracing methods based on graph processing techniques. Combining graph processing techniques and traveltime calculation, modern ray tracing methods mainly include: interpolation method (Asakawa & Kawanaka, 1993; Cardarelli & Cerreto, 2002; Nie & Yang, 2003); shortest ray path tracing method (Moser, 1991; Bai, Greenhalgh & Zhou, 2007; Sun Z., Sun J., & Han, 2009). Methods of the kind obtain the viscosity solution of the eikonal equation through numerical analysis Their calculation efficiency is high, but their defect is striking, in that, their calculation accuracy is low especially in the area near the source. Based on the advantages and disadvantages of FMM and WFC, this paper puts forward a joint traveltime calculation method for deep-sea geology. The above conclusions are verified through the error analysis of the homogeneous model and the trial of the gradient model, the layered model, the Marmousi model, and Sigsbee model
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