| Title | Development of a Non-Volcanic Hydrothermal System Caused by a Permeable Fracture Zone |
|---|---|
| Authors | Yasuhiro Fujimitsu, Daisuke Oka, Sachio Ehara, Akira Ono |
| Year | 2008 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | non-volcanic hydrothermal system, fracture, fault, earthquake, numerical model |
| Abstract | We conducted some numerical model simulations for development of a nonvolcanic hydrothermal system caused by a high permeability fracture zone formed by seismic activity. We set a permeable fracture zone that has a height of 12 km and exists 3 km below ground surface. The width (4 km, 6 km), extension (16 km and 28 km) and permeability (1 md, 10 md, 100 md) of the fracture zone were set as parameters of the simulations. The results of the simulations up to 100,000 years after formation of the fracture zone show that relatively strong convection occurs in the fracture zone in the early stage of the development process, and changes to weaker one. And temperature homogenization in the zone and groundwater flow outside of the zone progress with time. The result of the simulation up to 1,000,000 years shows that weak convection spreads and cools over a wide area out of the fracture zone. Therefore, it is inferred that a non-volcanic hydrothermal system will be formed after formation of a permeable fracture zone and the distributions of underground temperature and groundwater flow will change in the long term even if no hydrothermal feature appears just after the seismic events. |