BASEMENT EXHUMATION IN LATER STAGES OF ARC-CONTINENT COLLISION REVEALED BY ACTIVE SOURCE SEISMOLOGY: AN EXAMPLE FROM NORTH OF HUALIEN ALONG THE EAST COAST OF TAIWAN

The later stages of arc-continent collision are characterized by complex tectonic processes, including basement exhumation, crustal deformation, and sedimentary basin evolution. North of Hualien, Taiwan, represents an ideal natural laboratory to investigate these processes due to its unique geological setting at the active boundary of the Philippine Sea Plate and the Eurasian Plate. Using active source seismology, we present new insights into the structural configuration and mechanisms driving basement exhumation in this region. Our study integrates fieldwork, along with 20 km of seismic reflection and refraction profiles to image crustal structures, revealing exhumation of basement rocks. Key findings include evidence of doubly vergent thrusts in the basement in the foreland area, folding of overlying sediments, and the localization of deformation along structural discontinuities. These features reflect the interplay between tectonic contractional deformation not only along the closed forearc basin, but also in the foreland, causing exhumation of basement materials along the retrowedge. Preliminary results show that some of the exhumed basement rocks have very high P-wave velocity, greater than 6.5 km/s. The results highlight the role of active tectonics evolution of collisional margin, showing evidence of brittle deformation overprinting the exhumed ductile deformation. This provides additional constraints on the geodynamic models of arc-continent collision in Taiwan. This work advances our understanding of how collisional processes impact crustal architecture and has broader implications for interpreting similar tectonic settings globally.