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Triangular mesh ray tracing global method of two-dimensional complex construction

A complex structure and ray tracing technology, applied in the field of exploration geophysics, can solve the problems of difficult medium speed changes, complex problems, difficult to realize, etc., achieve high precision and reliability, and overcome the effect of poor adaptability

Active Publication Date: 2009-09-16
CHANGJIANG GEOPHYSICAL EXPLORATION & TESTING WUHAN CO LTD
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

When Vidale (1988) proposed the finite-difference method of the equation, he pointed out that the main problems of the shooting method and the bending method are: ① It is difficult to deal with strong velocity changes in the medium; ② It is difficult to find the global minimum traveltime in the multi-valued traveltime ; ③The calculation efficiency is low; ④The ray coverage density in the shadow area is insufficient
However, these ray-tracing methods are mainly aimed at regular nets, and applying them to triangulated nets will complicate the problem and even make it difficult to implement
[0007] The advantages of triangulation make the parameterization of model triangulation an important trend in the parameterization of geophysical models in the future, but there is a lack of in-depth research on its wave field ray tracing. Therefore, the triangulation model and its wave field ray tracing are the most Physical detection technology is an important issue that must be solved to improve the efficiency and effect of forward modeling and inversion

Method used

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  • Triangular mesh ray tracing global method of two-dimensional complex construction
  • Triangular mesh ray tracing global method of two-dimensional complex construction
  • Triangular mesh ray tracing global method of two-dimensional complex construction

Examples

Experimental program
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Effect test

Embodiment 1

[0129] Example 1 Horizontal Layered Homogeneous Media Model

[0130] attached Figure 11 is the triangulation and ray tracing result of the horizontal layered model. The source point is located at the upper left corner, and the sink points are located at the upper, right, and lower boundaries of the model, respectively. The model is shown in the attached Figure 11 (a), the medium velocity of the first layer is 2000m / s, the medium velocity of the second layer is 4000m / s, the medium velocity of the third layer is 3000m / s, the medium velocity of the fourth layer is 5000m / s, and the horizontal width of the model is 50m , the thickness of the four layers in the vertical direction is 10m, and the model is triangulated by a function with a density of 2m. attached Figure 11 (a) is the triangulation result, attached Figure 11 (b) is the wave front and ray path at different times obtained by this algorithm.

Embodiment 2

[0131] Example 2 Model with voids

[0132] attached Figure 12 Triangulation and ray tracing results of a model with holes. The source point is located at the upper left corner, and the sink points are located at the upper, right, and lower boundaries of the model, respectively. The model is shown in the attached Figure 12 (a), the background velocity is 4000m / s, setting: low-velocity rectangular area with velocity of 2000m / s, high-speed rectangular area with velocity of 5000m / s and tunnel-shaped cavity, grid division adopts non-uniform density control function. attached Figure 12 (a) is the triangulation result, attached Figure 12 (b) is the wave front and ray path at different times obtained by this algorithm.

Embodiment 3

[0133] Example 3 Model with faults

[0134] attached Figure 13 Triangulation and ray tracing results for a model with faults. The source point is located at the lower left corner, and the sink points are located at the outer boundary of the model, respectively. The model is shown in the attached Figure 13 (a), the fault sub-domain Ω is set in the region 2 and the low-speed subfield Ω 5 , for the analog Ω 3 to Ω 5 Gradient changes with larger speeds increase the mesh refinement subfield Ω 4 , the grid subdivision adopts the non-uniform density control function, and the simulation speed of each subdomain Ω 1 : v p =3000m / s,Ω 2 :v p =2000m / s,Ω 3 : v p =4000m / s,Ω 4 : v p =4000m / s,Ω 5 : v p = 3000m / s. attached Figure 13 (a) is the triangulation result, attached Figure 13 (b) is the wave front and ray path at different times obtained by this algorithm.

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Abstract

The invention relates to a travel tomographic inversion of two-dimensional complex construction and a ray tracing method of wave field calculation based on Maslov ray theory. For two-dimensional complex external geometric boundary and complex space structure within domain, a medium is parameterized by using a triangle model with uniform slowness subblocks, and nodes are set on the boundary of a triangle unit. A traveling wave surface is used for replacing a wave front surface so that the expansion of the traveling wave surface and the transmission of the wave are transferred with the vibration of the triangle unit and the adjacent triangle unit, and can self-transfer backwards when encountering reverse branch without other shrinkage; the secondary source position of each node and the minimum travel time calculation are realized in the process of travel wave surface expansion; and the ray path from the receiving point to the source point is picked by using the travel time and direction information of each node secondary source and by means of the minimum travel time search. The calculation method is applied to any polygonal mesh.

Description

technical field [0001] The invention relates to a global method for ray tracing of a two-dimensional complex structure triangulation network, specifically a ray tracing method for traveltime tomography inversion of a two-dimensional complex structure and wave field calculation based on Maslov ray theory, belonging to the exploration of the earth field of physical technology. Background technique [0002] Ray theory and ray method are an important way to understand the law of wave field propagation, an important means to study wave field propagation in complex underground structures and inhomogeneous media, and also the basis of traveltime tomography inversion. [0003] Whether it is forward modeling or tomographic inversion, model parameterization is a fundamental issue. Due to the complexity of the site conditions of engineering geological exploration, the external geometric shape of the detected research objects is mostly irregular, such as the "I"-shaped structure; the i...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01V1/28G01V1/30
Inventor 刘润泽于师建张建清李张明张智陈华刘方文陆二男况碧波熊永红喻维钢李文忠余才盛周习军程含发丁亮清刘新志
Owner CHANGJIANG GEOPHYSICAL EXPLORATION & TESTING WUHAN CO LTD
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