Reflected Wave Tomographic Simulation And The Application In Xi'an Ground Fissures

Seismic tomography is developed on the basis of medical tomography. It refers to that, a kind of energy can be stimulated on the external obJect and go through the media. Receiving machine can get the medium inside information. And on some algorithm, utilizing computer graphic reconstruction can access to the 2-d or 3-d geological structure's information. Then it can detect geometric shape,acquire physical parameter's distribution of the internal structure,lock the abnormal body's position and so on. This process involves model parameters,positive calculations and inversion calculations.This thesis introduces in detail the seismic tomography's history (including positive and inversion). The improved shortest path algorithm (MSPM) combining with partition multistage computing technology is used in positive calculation and the conJugate gradient method solving the constrained damped least-square problems is used in inversion calculation. Thesis also gives the evaluation index of inversion accuracy. In the second part, we accomplish multiple waves tracking calculation in two-dimensional complex layer medium, and realize transmission wave, transformation wave and reflection wave's tracking calculation in two-dimensional layer model (including low-speed zone). In the third part, we simulate various layered media models, including the low speed model surrounded by high-speed body,fault model and graben model. At the same time, we analysis and discuss the inversion solution. The result shows that the convergence is very good and close to the real value. Finally, thesis introduces the reflected wave tomographic imaging being used in Xi'an ground fissures. On the basis of satisfied test mode, we process Xi'an ground fissures data. The result shows that we can overall accurately determine the ground fissures'position and tendency in the near earth's surface and verifies this algorithm is effective and has a certain practical value.