Ambient Noise Tomography Across the Taiwan Strait, Taiwan Island, and Southwestern Ryukyu Arc: Implications for Subsurface Slab Interactions

Abstract

AbstractThe subduction flipping in the Taiwan region leads to complexities in the lithospheric structure. To better understand the arc‐continental collision process in this zone, we construct a 3‐D lithospheric model of the Taiwan Strait, Taiwan Island, and southwestern Ryukyu Arc. In the middle to lower crust, low velocities are mainly located beneath the Ryukyu Trough and the rifted basins in the Taiwan Strait, and high velocities are imaged in the Kuanyin and Penghu Platforms. Likely, the Kuanyin and Penghu Platforms act as relatively strong barriers that block the persistent westward advance of the western deformation front of the Taiwan mountain belt, as manifested by shape of the deformation front that withdraws to the east in the basement highs. In the mantle, high velocities are observed beneath the Central Range and Ryukyu Arc, which is interpreted as the two oppositely oriented slab subductions, that is, subduction of the Philippine Sea slab in the northeast Taiwan and Eurasian slab subduction in south Taiwan. Based on the vertical transects through our 3‐D model, we find that the subduction polarity has flipped in north Taiwan, and the tectonic framework in central Taiwan is in the process of subduction polarity reversal. We also image significant low mantle velocities beneath the North Taiwan Volcanic Zone and Taihsi Basin, which may be related to the breakoff of the subducting Eurasian slab. In addition, we propose that the inherited weakness of the Taihsi Basin may have facilitated the slab breakoff in central Taiwan.