Possible splay fault slip during the 1946 Nankai earthquake

This paper considers seafloor deformation associated with the 1946 Nankai earthquake, which occurred in the Nankai Trough subduction zone off the coast of southwest Japan. We note that recent high-resolution determinations of the slip distribution, assumed to be confined to the plate boundary, result in a pronounced maximum in seafloor displacement midway between the coast of Shikoku and the trough axis. We show that this feature could be due to slip on a splay fault rather than the plate boundary. Such a model for the western part of the slip distribution is able to account for the main features of the tsunamigenic seafloor deformation obtained in previous studies, with a maximum slip consistent with the plate convergent rate and history of earthquake recurrence at the Nankai Trough.