Link between Crustal Magnetization and Earthquakes in Taiwan

Abstract

The active Taiwan orogen is located between the Ryukyu subduction zone in the northeast and the Manila subduction zone in the south. Intensive collision from the northwestward motion of the Luzon Arc has induced enormous earthquakes in and around Taiwan. In this paper, we attempt to relate the occurrence of earthquakes in Taiwan to crustal magnetization. For that, we have inverted magnetic anomalies to obtain an equivalent crustal magnetization distribution in the Taiwan region. In general, high magnetization zones are considered as relatively rigid zones. In contrast, weak zones can be compressed as a result of lateral plate convergence, causing intensively crustal deformation and earthquakes. The Lukang Magnetization High (LMH), located in mid-west Taiwan, is suggested to dominate earthquake occurrence in middle Taiwan. Historically large earthquakes in Taiwan are mostly distributed around the eastern side of the LMH. If we take into account the northwestward convergence of the Luzon Arc or the Philippine Sea Plate, the area to the southeastern side of the LMH actually incubates more earthquake hazards. The crust of relatively low magnetization in mid-central Taiwan has been compressed and escaped sideward; intensive compression has also caused thicker crust and the depths of crustal earthquakes in middle Taiwan may be as deep as 40 km. Although both the eastern Central Range and the Luzon Arc show relatively high magnetizations, the Luzon Arc may be intrinsically less stable because of its younger and hotter nature; thus, the Luzon Arc has historically displayed severe internal deformation and produced numerous earthquakes as a result of plate collision.