The Study Of Underground Structure And Geophysical State In Geothermal Areas By Seismic Exploration

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Journal Article: The Study Of Underground Structure And Geophysical State In Geothermal Areas By Seismic Exploration

Abstract
During the last several years, seismic prospectings have been conducted in some geothermal fields (Matsukawa, Otake and Onikobe) in Japan. In Japan, all of the geothermal fields are in volcanic areas, consequently mostly reflection techniques and partly refraction ones have been applied because of the complicated velocity distributions in such geothermal fields. From these field data, some interesting information has been obtained, however generally speaking, it is rather difficult to distinguish the feature of cap rock, hot fluid reservoir and fault structures and to get deeper information related to heat sources from these complicated data. From such view points, recently, two techniques have been tried, the first one is to remove the undesirable noises and multiple reflections so that we will be able to make clear the deeper structure, by using digital data processing including the newly established software. The second one is to use not only the conventional arrival times, but also to utilize the absorption of wave energy caused by the fluid viscosity and high frequency, and to study the wavelength of a seismic wave to presume the geophysical state in such geothermal fields. From the first one, in some geothermal fields, a very interesting deeper structure (about four kilometers' depth) which may indicate the structure related to the heat source, has been obtained, and from the latter, it has become clear that the areas where low frequency wave patterns predominate, correspond to the fluid reservoir. With regard to the absorption, it is under study. By comparing these seismic data with the related geological, geophysical and geochemical data, the application of a seismic method will be surely increased not only to find the suitable area for the utilization of natural steam from volcanic areas for electric power generation, but also to know the underground geothermal characters of those areas.

Author 
M. Hayakawa








Published Journal 
Geothermics, 1970





DOI 
Not Provided
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Citation

M. Hayakawa. 1970. The Study Of Underground Structure And Geophysical State In Geothermal Areas By Seismic Exploration. Geothermics. (!) .