Seismic velocity structure of the Taiwan mountain belt along TAIGER transect T5

Convergence between the Philippine Sea Plate, and the Chinese continental margin has led to the formation of the Taiwan mountain belt over the course of just 6.5 Ma or less. In central Taiwan, the north-south trending Longitudinal Valley marks the suture between the volcanic arc rocks of the Luzon arc to the east, and continental basement and sedimentary rocks of the incoming Eurasian Plate to the west. Recent analyses of seismic reflection and refraction data from the 2008 and 2009 TAIGER seismic experiment have shown that the extended continental crust of the Chinese margin accretes to the overriding Philippine Sea Plate in southern Taiwan, where the arc-continent collision is still in its early stages. In central Taiwan, however, thicker continental crust of the continental shelf enters the orogen, which reaches a larger width and elevation here than in the south. Seismic transect T5 of the TAIGER project was oriented perpendicular to Taiwan from the Strait across the whole orogen, . We use travel times from air-gun shots from the R/V Marcus Langseth, from an on-land explosion, and from regional earthquakes recorded on an array of land and ocean-bottom seismometers along this seismic transect. The combination of active-source and earthquake seismic data together provides the necessary spatial coverage to image the crustal root of the orogen. By including clear Moho reflection arrivals, the detailed seismic velocity structure along T5 will help us constrain the crustal-mantle boundary as well as the seismic velocity variations in sedimentary, metamorphic and igneous rocks. Two of the key issues that we seek to address in the interpretation of our seismic refraction data are the fate of the forearc of the Philippine Sea Plate in the collision, and the role of the crystalline basement of the Chinese margin in the uplift and exhumation of the Central Range.