3D Traveltime Calculation Using SWEET and ESD Algorithms
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Solution Overview
Problem
Conventional 3D traveltime calculation methods using the SWEET algorithm are inefficient for shallow depth sources due to high computational costs when using coarse-grid mesh, as they struggle to accurately simulate wavefields with large grid spacing.
Innovation Solution
The proposed method combines the SWEET algorithm with the equivalent source distribution (ESD) algorithm and uses a coarse-grid mesh to calculate 3D traveltime by calculating Green's function, equivalent source vectors, wavefield vectors, and partial derivatives, allowing for efficient first-arrival traveltime calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional SWEET algorithm is used for shallow depth source, then traveltime calculation can be performed, but computational time is excessively long and accuracy deteriorates with coarse-grid mesh
Solution Approach 1:
The patent segments the wavefield calculation into two distinct parts: (1) calculating Green's function on a coarse grid to obtain wavefield at source locations, and (2) using equivalent source distribution to propagate this wavefield to receiver locations. This segmentation allows each part to be optimized independently, resolving the contradiction between accuracy and computational efficiency.
Solution Approach 2:
The patent introduces Green's function as an intermediary between the source and receiver. By first calculating the wavefield at source locations using Green's function on a coarse grid, and then using this intermediate result to compute receiver wavefields through equivalent source distribution, the method avoids direct fine-grid calculation while maintaining accuracy.
2Productivity
If coarse-grid mesh is used for computational efficiency, then calculation speed improves, but accuracy of shallow depth source simulation deteriorates
Solution Approach 1:
The patent applies different grid qualities to different spatial locations: coarse-grid mesh is used for regions away from the shallow source where computational efficiency is prioritized, while the equivalent source distribution technique effectively captures the fine-scale physics near the source. This local differentiation resolves the contradiction between speed and accuracy.
Solution Approach 2:
The patent changes the grid spacing parameter from fine to coarse, but compensates by introducing the equivalent source distribution formulation. This parameter change allows coarse-grid mesh to be used without sacrificing the ability to accurately represent shallow depth sources, thus maintaining both speed and accuracy.
3Measurement precision
If fine-grid mesh is used for accurate shallow depth source simulation, then accuracy improves, but computational cost increases dramatically
Solution Approach 1:
The patent transitions from a direct spatial discretization approach to a dual-domain approach by first computing in the spatial domain (Green's function on coarse grid) and then using frequency-domain techniques (equivalent source distribution) to propagate the solution. This dimensional change in the computational approach allows coarse-grid usage without sacrificing accuracy.
Data Source
AI summary
The present invention relates generally to an apparatus and method for calculating efficient 3-dimensional (3D) traveltime by using coarse-grid mesh for a shallow depth source. More particularly, the present invention relates to an efficient 3D traveltime calculation method for a shallow depth source by combining a suppressed wave equation estimation of traveltime (SWEET) algorithm and an equivalent source distribution (ESD) algorithm, wherein the SWEET algorithm is a traveltime calculation algorithm using an damped wave equation and the ESD algorithm is for equivalently distributed sources; and to an apparatus and method for calculating efficient 3D traveltime by using coarse-grid mesh for a shallow depth source which may need less calculation time compared with that of a conventional SWEET algorithm.