NEW STRUCTURAL INTERPRETATION OF THE DAII CHI-KASHIMA SEAMOUNT (JAPANTRENCH) AND SUBSEQUENT GEODYNAMIC HISTORY

The Daiichi-Kashima seamount is subducting into the Japan Trench. A 1, 500 m scarp cuts the volcano in two parts. The north-west flank is col lapsed and has been largely subducted under the Japan margin. The anal ysis of seismic profiles and submersible dives, complemented by sandbo x modelling, allows us to propose a new interpretation of its internal structure. The results of these studies show that the present morphol ogy of the Daiichi-Kashima seamount is due to collapse of the north-we st flank, along a listric fault inherited from past volcanic activity. The listric fault and other normal faults are reactivated due to the flexure of the subducting plate.