資源探査に関する研究の動向と大規模データプロセッシング

[1K0101-06-06] Spatial distribution of subsurface hydrothermal alteration zones in the Wayang Windu geothermal field, Indonesia, based on audio-frequency magnetotelluric survey

○Tada-nori Goto Goto¹, Yuji Yamada¹, Mohamad Nur Heriawan², Irwan Iskandar², Katsuaki Koike¹ (1. Graduate School of Engineering, Kyoto University, 2. Institut Teknologi Bandung)

司会：桑谷 立（海洋研究開発機構）、木崎 彰久（秋田大学）

Keywords:Magnetotelluric method, Hydrothermal alteration zone, Resistivity

In the Wayang Windu geothermal field, Indonesia, the hydrothermally alteration zones are detected based on the remote sensing, which are located near the of topographical lineaments. The alteration zones are also characterized as high radon anomalies in soil gas. These foundings imply that fracture zones in this field play an important role for path way of deep high-temperature fluid to the land surface, and also have a potential of deep hydrothermal reservoirs. For verification of this hypothesis, geophysical surveys at the ground surface of the Wayang Windu field with the non-destructive way are useful. In this study, we conducted the audio-frequency magnetotellurics (AMT), which is one of the electromagnetic geophysical surveys in Wayang Windu. Since the resistivity greatly decreases at buried water-rich/clay-rich geological zones, the AMT survey is known to be a powerful tool for imaging the fracture zones and related hydrothermal alteration zones beneath the geochemical anomalies. The AMT data were obtained at 38 sites in northern and middle of the Wayang Windu field. In the preliminary result, we found that low resistivity features are obvious at junctions of topographic lineaments. Some of them are located close to the manifestations. Our result possibly can indicate fracture zones with the deep and high-temperature gas/water upwelling.