Discrimination of coherent waves by a downhole double three component seismic detector

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(a) Development of double detector : We developed a downhole double three component detector using two three component detectors which have been designed and manufactured at Tohoku University. In-situ calibration the detector was carried out in Tohoku University Higashi-Hachimanatai Field. It has been revealed that the detector has a detectability of hodogram up to 200 Hz.(b) Investigation on signal processing : A method which enables coherence analysis of the three dimensional hodogram. A spectral-matrix-based method (3D-TFC) showed good potential for this purpose.(c) Field measurement : We carried out a field measurement of AE at Kakkonda Geothermal Field and recorded AE events with good quality.(d) Analysis of field data : Coherent phase, including direct arrival and reflected, in the AE events from Kakkonda were detected by the 3D-TFC method. The result was consistent with other geological information and reflection survey.