The Base of Gas Hydrate Stability Zone and the Anomalous Sediment Thermal Conductivity Offshore of SW Taiwan

We have collected 80 sites of heat flow data for many years over Bottom Simulating Reflectors (BSRs) appeared on the seismic profiles collected from continental slopes and rises offshore of southwestern Taiwan. The Bases of Gas Hydrate Stability Zones（BGHSs）estimated by thermal gradients agree with BSRs except the data obtained from shallow penetration.e found two abnormal phenomena that maybe due to the hydrate bearing sediment.One is we could not detect the temperature rise induced from the friction heat when the Lister-type heat probe was inserted into seafloor sediment over BSR and the other one is we found the thermal conductivity very high at the beginning, but gradually decreased to a stable vaule when measuring it with a needle probe in a laboratory on board the ship. These could mean the gas hydrate dissociation and endothermic process occurred due to penetration friction heat, temperature increase, and pressure decrease. These two phenomena, in general could be taken as an indication of gas hydrate bearing sediments. However, we also found one site on area covered by the extremely soft and loose mud spurted by the mud diaper without penetration friction heat raised temperature. n order to prove our hypothesis, we did experiments in constant temperature baths, numerical modeling, and compared the thermal conductivities measured by the Lister-type heat probe and that by the needle probe at the same site. The results confirmed the hypothesis.