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

(A)双探测器的研制：利用东北大学设计和制造的两个三分量探测器，我们开发了井下双三分量探测器。探测器的现场校准是在东北大学东八里田进行的。据透露，该探测器具有高达200赫兹的热像检测能力。(B)信号处理研究：一种能够对三维热像进行相干分析的方法。基于谱矩阵的方法(3D-TFC)显示出很好的潜力。(C)现场测量：我们在Kakkonda地热田进行了AE的现场测量，记录了高质量的AE事件。(D)野外数据分析：用3D-TFC方法检测到Kakkonda的AE事件中的相干相位，包括直接到达和反射。这一结果与其他地质资料和反射调查结果一致。

(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.