本研究の対象地域は，オルカリア地熱地帯東部および南西部地区である。オルカリア地熱発電所はケニア初の地熱発電所であり，設備容量15MWeのUnit Iが1981年に運転を開始した。これまでの調査・研究では，オルカリアの地熱系は断層系に支配されていることが示されている。本研究は，ランドサット8の画像解析に基づき地表面の放熱量を把握することを目的とした。解析には2015年7月11日に取得されたUSGSのランドサット8のデータを使用した。解析の結果，最高15.2862℃を示す地表面温度異常が抽出され，この最高温度から11.3432℃までの範囲が噴気地等の地熱徴候によるものと推定された。また断層構造に沿った0.1494km²の区域に0.4459MWの放射熱損失が生じていることが見積もられた。本研究では，発電プラントなど地熱活動に関連しない温度異常を解析において除外し，熱異常の検出精度を高めた。

In order to examine the performance of three-dimensional (3D) inversion of magnetotelluric (MT) data for geothermal exploration, where accurate numerical modeling is necessary against rough topography variation, we have utilized two inversion codes, FEMTIC and WSINV3DMT, for 3D inversion of MT data obtained in a geothermal area near the Hakkoda volcano, northern Japan. FEMTIC, a finite-element modeling (FEM) code, can incorporate either tetrahedral elements or deformed non-conforming hexahedral elements in the 3D mesh, while WSINV3DMT, a finite-difference modeling (FDM) code, uses rectangular cells. We used the same subset of the MT data (all components of the impedance and tipper at 15 frequencies at 34 stations) for both inversions, with the same noise-floor setting. As a result, we have recognized that the resistivity model by the WSINV3DMT code produce small but extremely high- or low-resistivity anomalies at the ground surface and resistivity distribution becomes rough. In addition, several thin horizontal anomalies of high- and low-resistivities alternately appear in shallow parts. These anomalies seem to be due to numerical errors by the rectangular approximation of the boundary between the air and the ground. In contrast, the FEMTIC code does not have significant numerical errors by the approximation of topographic changes, and no such anomalous structures appear in shallow parts and the resistivity distribution at the surface is smooth. For deeper parts, models by FEMTIC and WSINV3DMT are generally similar, however, the shapes of the main low-resistivity layer, which corresponds to the clay cap of geothermal reservoirs, are different between them. The WSINV3DMT code tends to generate extreme resistivity anomalies in the deeper parts. Comparison with resistivity logging data in geothermal exploration wells shows better matching for the FEMTIC models than the WSINV3DMT models. These investigations suggest that the FEM inversion is more reliable than the FDM when we include the topography in the 3D MT inversion.

The number of countries which deploy ground source heat pump (GSHP) has been linearly increasing these 20 years. It means that GSHP can be applied almost everywhere on the globe but there are still many regions in which GSHP is not known and it has not been used yet. Meanwhile the world total GSHP capacity is increasing exponentially, showing that a quite rapid growth is possible once the value of GSHP is well known in the region.

This paper shows statistic data on GSHP use of the world and of individual leading countries. There exists geographical bias of GSHP installation, not necessarily due to climate condition but due to cultural and economic ties of the nations. Histories of its deployment in leading countries revealed that there were policy supports on GSHP installation in most cases. In China, the federal government sets high national goals for its deployment and municipals put them into practice. In the USA, various financial supports were given to GSHP installation by state or municipal governments pushed by a private sector. In Switzerland and in Korea, it was obliged to apply one of energy saving systems for new buildings and GSHP had been chosen by majority of users. Considering the current publicity of GSHP in Japan, obligation type of policy support would be most effective for rapid growth of GSHP installation.