Fault tectonics of the Coastal Range, eastern Taiwan

The Coastal Range in eastern Taiwan is an exotic terrane along the Asian Continental Margin. It was formed by an oblique collision between the Luzon volcanic arc of the Philippine Sea plate and the Asian continent. Substantial fault-slip data were collected from 195 stations in the Range for determining the type and amount of structural deformation. Inversion of fault-slip data shows that σ₁ is nearly horizontal with the azimuth ranging between 90°-150°; the median σ₁ plot has a trend of 127°. This is consistent with the results derived from the present-day plate motion. However, through detailed investigation, different stress states can be differentiated. They were correlated with different evolutional stages of deformation of the Range. The extensional events recorded in the Tuluanshan Formation probably represent the deformation during subduction or at an early stage during collision. The first compressional event with σ₁ of about 140°represents deformation during the collision stage. The second compressional event with σ₁ of about 120°represents deformation during the accretion stage, after the volcanic arc rotated 20°-40°clockwise.