4. Data Processing/Signal Processing
Interferometric Cross-hole Tomography
Kentaro Torii(1), Kazuya Shiraishi(1), Kyosuke Onishi(1), Toshifumi Matsuoka(1), Toshinori Kimura(2) and Takao Aizawa(2)
(1) Kyoto University Faculty of Engineering Department of Civil and Earth Resources Engineering, Japan. (2) Suncoh Consultants Co. Ltd., Japan.
Abstract
In order to realize the interferometric cross-hole tomography, we make lab experiments in this paper. Plural sources are set in a certain interval at the free surface, and plural receivers are set underground. A virtual sources is synthesized at an arbitrary receiver position by cross-correlating its record with others. At first, wave propagation from a source at the free surface is recorded at each receiver. Such measurements are intermittently made from first source to final source. After recording all sources¡Ç wave propagation, cross-correlation processes are made against all sources¡Ç records. And then, results of each cross-correlation are summed up. Thus, we can get VS records. In order to consider the validity of VS records, wave propagation from a source at VS position is recorded. And we compare these records with VS records. In this study, we make indoor experiments with water tank and numerical simulations using finite deference method in order to improve this VS method and apply to cross-hole tomography. Indoor experiments are made under acoustic conditions. So we do not have to analyze S-wave and simplify records for picking. An anomaly is set between wells. Moreover, numerical simulation is done under same conditions with indoor experiments. In the results, we successfully synthesized the new records, which are similar to records whose source is set at a well. In conclusions, we can apply VS method for cross-hole tomography. Using VS method and large-energy source on the free surface, it is expected to improve the signal-to-noise ratio, to expand the distance of wells and to make 4D measurement. In the next stage, we develop VS method with respect to array of sources and data processing procedures, and finally make cross-hole tomography.
Last modified: Thu May 25 10:01:13 2006