Deveropment of high resolution tomography method based on coherent seismic wave

我们开发了一种基于新品牌理念的主动地下层析成像系统。在1997财政年度，我们建立了测试系统，准备制造震源，这是本研究的中心。在1998财年，我们制造了该源并将其安装在测试系统中。我们一直在运行它并进行了改进。(1)建立了精确控制人工震源的原型模型。在这个源中，一个电动伺服电机驱动一个偏心质量。旋转的频率保持非常恒定。因此，源可以发射非常纯净的正弦波。(2)建立了由高灵敏度反馈地震仪、放大器、AD转换器和PC机组成的传感器单元原型模型。该PC机管理AD转换的时序，并通过堆叠压缩数据。我们还发展了为分析数据提供基础的数学理论。提出并试验了几种弹性波场数值分析方法，包括多层介质半解析法和有限差分格式。我们已经计算了许多正问题。(4)我们尝试建立一种新的反演算法来估计地下结构。然而，有必要建立一个简明的弹性波在非弹性区域的散射模型。我们对这一现象制定了新的实验研究计划。

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.