Deveropment of high resolution tomography method based on coherent seismic wave

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We have developed an active underground tomography system based on a new-brand idea. In 1997 fiscal year, we set up testing system and prepared the manufacturing of a seismic source which was the center of the present research. In 1998 fiscal year, we manufactured the source and installed it in the testing system. We have been running it and made improvements.(1) We established a prototype model of the accurately controlled artificial seismic source. In this source, an electric servomotor drives an eccentric mass. The frequency of the rotation is maintained extremely constant. As a result, the source could emit very pure sinusoidal wave.(2) We established a prototype model of a sensor unit, as a combination of high sensitivity feedback seismographs, amplifiers, AD converters and a PC.This PC manages the timing of AD conversion and condenses the data by stacking.(3) We also developed mathematical theory which affords the basis for the analysis of data. We made and tested several numerical analysis methods of elastic wave field including a semi analytic method of multi-layer medium a finite difference scheme. We have calculated many forward problems.(4) We attempted to build a new inversion algorithm that estimated the under ground structure. It was revealed, however, necessary to prepare a concise model of scattering of the elastic wave by inelastic region. We established a plan of new experimental study of this phenomenon.