Formation of the Taiwan Island as a Solitary Wave along the Eurasian Continental Plate Margin: Magnetic and Seismological Evidence

The Philippine Sea plate moves northwestward, with respect to the Eurasian plate, and produces the Ryukyu subduction system (including the Ryukyu trench, the Ryukyu arc and the Okinawa trough) and the Manila subduction system (including the Manila trench and the Luzon arc) with opposite polarity of subduction on the plate boundary along the Ryukyu-Taiwan-Luzon region. The transition zone between these two subduction systems is the Taiwan island, with vigorous mountain building in the south and gravitational collapsing in the north. Thus, the Taiwan island propagates southwestward as a solitary wave along the Eurasian continental plate margin, with a speed of about 7 cm/y. In this paper, we describe the occurrence environment for this phenomenon, with morphological, magnetic and seismological evidence. The shifting oblique lithospheric convergence of the Philippine Sea plate with the Eurasian continental plate margin causes the transient solitary wave of the Taiwan island. The convergence has squeezed the tectonic zones near the plate boundary tightly and uplifted the transition zone that is the Taiwan island. When the convergence site migrates southwestward along the continental plate margin, the squeezed parts of these tectonic zones are released again and spread, by the following tensional stress due to the northward subduction of the Philippine Sea plate. Therefore, the area of the Taiwan island does not necessarily increase substantially with geological time. In order to better understand the lithospheric interaction in the Taiwan area, we also proposed a lithospheric convergence model in this paper.