TEMPERATURE LOGGING IN A SEISMIC FAULT ZONE——AN CASE OF ODP186

The ODP186 acquired temperature logging and other data from the Japan Trench seismic fault zone. We calculated the temperature gradient with temperature logging data, and the heat generation rate with radioactive data in order to understand the relation between the seismic fracture zone and the temperature and heat generation rate. Our results show that the measured temperature at the fracture zone is lower than the temperature in equilibrium condition, due to the cooling effect of mud circulation. And vice versa, the geothermal gradient attenuates with depth above the fracture zone, and increases slowly with depth beneath the fracture zone as expected.In the fracture zone, the heat generation rate is relatively high due to the high content of radioactive elements in the clay filled in the fractures. In this regard, the geothermal gradient could be used as a macroscopic indicator of fracture distribution range, and the heat generation rate reflects the microscopic distribution pattern of a fracture zone.