| Title | Temperature Gradient Map of the Hakkoda Gidl'hermal Area |
|---|---|
| Authors | Okubo, Y. and Muraoka, H., |
| Year | 1988 |
| Conference | Japan International Geothermal Symposium |
| Keywords | |
| Abstract | Ninety-nine ooreholes temperature log data in the Hakkoda geothermal area were gathered. 'file data were obtained from many kinds of ooreholes of geothermal and mineral exploration and hot spring prospecting. Standing time of temperature logging of geothermal exploration was 24 hours or more, but most of hot spring data has no description of standing time. In addition, Depths of logging range from several tens to 1500 meters depth. Therefore, reliability of the data is not uniform. We divided the data into six classes based on the depth and condition of logging such as standing time and stability of the data. Cosidering reliability of the data, we drawn the temperature gradient contour lines by hand(Figure 1). Background temperature gradient of the map ranges from 40°C/km to 50°C/km, and high teinperature gradient regions over 100°C/km occUr over the Hakkoda volcanoes(which is a Quaternary volcano group) and the Okiura and lloni hot springs. The value of the background corresponds to the average temperature gradient of the backarc side of the Japanese Islands(Okubo et al., in press). Figure 2 shows the relation between anion indexes and temperature gradients. High anion in~ values indicate high probability of heat sources•. High temperature gradient zones roughly correspond to anion index value highs. Figure 3 shoWs the relation between gravity map and temperature gradients. Gravity highs occur around theHakkoda volcanoes, while gravity lows occur to the west of the volcanoes. That is, a north-=south trending gravity changing area extends on the west edge of the volcanoes. This suggests that faults or tectonic lines can occur. A high temperature zone extends north on the north-west of the volcanoes, which correlates Well to the gravity changing area. Movement of geothermal fluid may be controlled by the faults or tectonic lines. |