Insights into the seismogenic structures of the arc-continent convergent
boundary in eastern Taiwan
Abstract
Taiwan’s doubly vergent orogen is a relatively young and active
arc-continent collision caused by the convergence of the Eurasian and
Philippine Sea Plates occurring along a complicated seismogenic plate
boundary. This study aims to investigate the evolutionary and tectonic
features of the retro-wedge, which is involved in uplifting and
shortening the growth of the Taiwan orogen. We delineate three potential
seismogenic structures: the Longitudinal Valley Fault (LVF), the
Ludao–Lanyu Fault (LLF), and the Central Range Fault (CRF) along the
convergent boundary by using seismic tomographic image and relocated
seismicity. We first discovered a west-dipping backthrust of the CRF
bounding on the eastern Backbone Range, which can be traced to a
distance of 300 km from the north Hualien city to the southeastern
offshore. The fault led to the development of a crustal scale pop-up
structure and resulted in the formation of a doubly vergent orogenic
wedge in the retro-wedge side. Thus, the generation of the
basement-involved backthrust has been attributed to the indentation of
the exhumed forearc mantle wedge and remnant forearc crust into the
Backbone Range during collision. As a result, the plate boundary
consists of two opposite vergent thrust systems of the LVF–LLF and CRF
that developed during the collision, following the closure of the
forearc basin of the North Luzon Trough and Longitudinal Valley from
incipient to mature collision, respectively. Our results provide new
tectonic features along convergent zone constraints for geodynamic
models of arc-continent collision allowing investigations of current
mountain building in Taiwan.