Résumé
Large benthic chemosynthetic communities have been observed at four main locations during the Kaiko submersi- ble dives in the Japanese trenches. They appear to be associated with venting along fractures. The first site for our observation was along the Japan and Kuril trenches, where the continental margin is eroded by the subducting plate and collapses into the trench. The benthic communities there seem to be related to tension gashes parallel to the subduction vector. The other communities were found on the toe of the Nankai accretionary prism, along the frontal thrust and tension gashes. The temperature anomafy associated with one of the communities is modeled to constrain the upward flow of interstitial water. As the anomaly has a small spatial extent and as the peak thermal gradient is high, the best fitting model is to be found in a vertical upward flow at a velocity of 100 m/yr in a cylindrical conduit leading out of an underlying shallow thrust.