| Title | ON THE AIRBORNE SURVEY BY A HELICOPTER- A BRIEF OUTLINE AND SEVERAL ANALYSES OF THE SURVEY |
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| Authors | T. Tosha, H. Inagaki, S. Soengkono and Y. Kida |
| Year | 2017 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Airborne survey, Gravity measurement, Spatial filter, Shape Index, Kuju geothermal field, Variogram, Fault structure |
| Abstract | Heat discharge areas, where many geothermal features are found and high geothermal potential are expected, are often located in the mountain areas near volcanoes. It is hard to carry out ground explorations in these areas because of difficult access and high elevation changes. Moreover, the volcanic area is designated as a national park in many areas. Nearly 80% of the geothermal resources are presumed to exist in the natural parks. Recently the deregulation of the geothermal development at Japanese national park was announced to encourage the development of geothermal energy for the energy security as well as combating global warning. With this announcement we are now able to develop geothermal resources at the lower category of the national park. Airborne geophysical survey is an effective method to acquire data from wide area without modification of the land surface. The survey using a helicopter has been conducted to obtain more scientific data for the exploration of geothermal prospects in the mountain regions near national parks. Two kinds of surveys are organised. One is the survey using the gravity gradiometer, which measures partial gradients of the gravity, and the other is the magneto-electric measurement by the TEM (transient electromagnetic) method. We can expect to detect the fracture structure by the gravity gradient measurements and the extension of the conductive cap-rock by the TEM method over the geothermal fields. As of 1st June 2017, 12 areas have been surveyed by the airborne gravity gradiometer and 10 areas by the airborne TEM. In this paper we will show some results with spatial filter technique and a simple analytical method based on the theory of geostatistics to the gravity gradient data to reveal fracture and fault structures in the geothermal field. |