The images of subduction slabs in the Taiwan region

A three-dimensional tomographic inversion using high quality data recorded by the central Weather Bureau Seismographic Network (CWBSN) was conducted to obtain clear and reliable images in the regions corresponding to the subduction slabs and to understand the tectonic environment of the Taiwan region. High velocity zones with a velocity perturbtion of about 5% relative to the surroundings are found. These zones correspond to the subduction Philippine Sea Plate in northern Taiwan and to that in southeastern Taiwan. The image profile along the longitude of 121.5°E shows that the Philippine Sea Plate starts subducting at the latitude of 24°N at the depth of about 40km and extends to the depth of 80km at the latitude of 25°N. Several image profiles along various latitudes show that the Eurasian Plate starts to subduct at longitude 120.8°E at a depth of 40km. The tectonic activity to the south of 22.9°N and to the north of 23.5°N is mainly dominated by the subducting slabs, while within the range, it is mainly dominated by the active collision of the two plates.