| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 2003: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2002: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2001: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Research Abstract |
There are clear contrasts in hot springs and earthquakes between San'in and San'yo areas, western Japan. Many hot springs of high temperature more than 50℃(up to 93℃) flow out in San'in area while no high temperature springs more than 50 can be seen in San'yo area. Earthquakes occur frequently in San'in area, while very few earthquakes occur in San'yo area. These contrasts may be owing to tectonic conditions. High temperature springs in San'in area may be due to deep circulations of meteoric water through fractured system in granite basement, while no deep water circulation may occur in San'yo area because the granite basement may be poorly fractured. In San'in area, in other words, deep water circulation in a large scale may occur through fractured system with hydraulic 'potential gradient produced by Chugoku Mountains of high altitude. To clarify the relationship between the geothermal phenomena and the basement condition, isotopic study was made for hot spring waters, cold spring wa
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ters, groundwaters and river waters collected in San'in and San'yo areas.
бD and б^<80> of meteoric waters such as cold spring waters, groundwaters and river waters show a so-called "altitude effect". бD and б^<80> in high temperature water from San'in area, on the other hand, show relatively low as their altitude compared with meteoric waters, corresponding to those of meteoric waters at elevations higher than about 500 m. This suggests that hot spring waters in the San'in area are derived from Chugoku Mountains having altitudes of more then 1,000 m above sea level through deep circulations of meteoric water.
On the other hand, бD and б^<80> values of hot waters from deep bore holes more than 1,000 m deep in San'yo area are clearly lower than the lower limits of бD and б^<80> of meteoric water in the areas. This indicates that the deep thermal waters from San'yo area may not be the present meteoric water' but might be fossil water, suggesting that no deep water circulation may occur in San'yo area.
Consequently, geothermal phenomena are related closely to a degree of fractures in the basement and to a hydraulic condition such as the existence of high mountains. A good relationship between geothermal phenomena and seismology can be considered to be owing to the basement structure related to a stress field of a large scale. Less
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