抄録
Magnetization vectors of seamounts and edifices in the West Philippine Sea were determined with a direct searching method in the space domain using the topography and magnetic anomaly data at the sea surface. The data analyzed were surveyed by the Hydrographic and Oceanographic Department of Japan since the 1980s. Several seamounts in the eastern part of the Minami Daito Basin are magnetized in the N70°W to N80°W directions with negative shallow inclinations, whereas edifices of the Kyushu-Palau Ridge have directions of N30°W with downward inclinations. The paleolatitude of the Oki-Daito Ridge as a whole is 4.4°S±11.0° and that of the Amami Plateau and the Daito Ridge, 15.1°N±4.6° and 20.1°S±8.2°, respectively. These results are inconsistent with the proposed clockwise rotation of the West Philippine Sea exceeding 80°. Furthermore, the results also suggest that the Oki Daito Ridge was generated in the Southern Hemisphere and then migrated northward. The large shortening between the Oki-Daito Ridge and the Amami-Daito Ridge regions may suggest the convergence boundary between them.
