| Abstract |
The audio frequency magnetotelluric (AMT) method was applied in 2004, for detailed investigation of the reservoir at the Ogiri geothermal field, southern Kyushu, southwestern Japan. The AMT stations were arranged with an interval of about 150 m on a grid array whose size was approximately 1.5 km x 1.5 km. The number of AMT stations was 66. This survey was targeting an eastern expansion of the currently producing geothermal reservoir. There had been several stages of MT surveys conducted in the same are before. This report presents three-dimensional (3D) inversion of the AMT data, together with those existing MT data. The resultant 3D models are consistent with the MT models reported in the past. The boundary between the low-resistivity cap layer and the high-resistivity reservoir zone is more complicated in the AMT model than the MT models. This may suggest a capability of high-resolution survey by the AMT method. |