Monitoring Hot Spring Aquifer Using Repeat Hybrid Micro-gravity Measurements in Beppu Geothermal Field, Japan
- 651 Downloads
Repeat hybrid micro-gravity measurements were conducted to detect the gravity change caused by hot spring water production around Beppu in eastern Kyushu, Japan. An A10 #017 absolute gravimeter (Micro-g LaCoste) and a CG-5 #549 gravimeter (Scintrex) were used for this study in intervals of three to four months at eight gravity stations. According to the results obtained with the absolute gravimetry, a gravity change of up to 33 μgal was detected at the Beppu Geothermal Research Laboratory (BGRL) reference station. The observed absolute gravity was compared with the groundwater level, and there was a good correlation between the gravity changes and the groundwater level changes. Based on the precipitation, groundwater level, and soil character, the effect of the water content changes in the unsaturated zone was estimated precisely by using a Gwater-1D. This calculation can explain that the gravity seasonal changes were caused by the groundwater level changes. After removal of noise effects (e.g., tidal movement, precipitation, and shallow groundwater level changes), the residual gravity changes, which were measured by the relative gravimeter, were subdivided into two types of responses. Gravity changes up to 90 μgal were observed from April 2014 to July 2015. After that, gravity became stable, except for small seasonal changes.
KeywordsGravity change Hot spring reservoir Monitoring Sustainability
This research was financially supported by the project (No. 14200097), entitled “Human-Environment Security in Asia-Pacific Ring of Fire: Water-Energy-Food Nexus,” by the Research Institute for Humanity and Nature (RIHN), Kyoto, Japan.
- Chida N, Ikeda Y, Nakada T, Okada A, Une H (2000) 1:25000 Active fault map in urban area, Beppu, Geographical Survey Institute Japan. (in Japanese)Google Scholar
- Geological Survey of Japan, AIST (ed) (2014) Seamless digital geological map of Japan 1: 200,000. Jan 14, 2014 version. Geol Surv Japan, National Institute of Advanced Industrial Science and TechnologyGoogle Scholar
- Hoshizumi H, Ono K, Mimura K, Noda T (1988) Geology of the Beppu district with geological sheet map of 1:50,000. Geol Surv Japan (in Japanese with English abstract)Google Scholar
- Japanese Association of Groundwater Hydrology (1979) Handbook of groundwater.. (in Japanese)Google Scholar
- Matsumoto K, Sato T, Takanezawa T, Ooe M (2001) GOTIC2: a program for computation of oceanic tidal loading effect. Journal of the Geodetic Society of Japan 47:243–248Google Scholar
- Nishijima J, Saibi H, Sofyan Y, Shimose S, Fujimitsu Y, Ehara S, Fukuda Y, Hasegawa T, Taniguchi M (2010) Reservoir monitoring using hybrid micro-gravity measurements in the Takigami geothermal field, central Kyushu, Japan. Proceedings of the World Geothermal Congress 2010Google Scholar
- Sasada M (1984) Basement structure of the Hohi geothermal area, central Kyushu, Japan. J Japan Geothermal Energy Association 21:1–11. (in Japanese with English abstract)Google Scholar
- Sasada M (1987) Pre-tertiary basement rocks of Hohi area, central Kyushu, Japan. Bull Geol Surv Japan 38:385–422. (in Japanese with English abstract)Google Scholar