Seismogenic strain across the transition from fore‐arc slivering to collision in southern Taiwan

Abstract

Tectonic slivers have profound implications on the mechanical behavior of fore arcs and subduction zones. Southern Taiwan is characterized by precollision fore‐arc slivering that likely exerts important controls on the evolution of collision. Inversion of focal mechanism solutions for seismogenic strain reveals spatially partitioned plate motion south of Taiwan, with dip‐slip faulting nearer the Manila trench and strike‐slip faulting nearer the Luzon arc. To the north these kinematics are less clearly segregated, and both types of faults appear to occur in the same volume of crust. Further north deformation is dominated by oblique slip on potentially reactivated steep reverse faults in the collision zone. Existing work on the active fault zones in Taiwan suggests that the subduction‐to‐collision transition is marked by a releasing step between the strike‐slip fault that bounds the fore‐arc sliver and the oblique thrusts of the collision zone. This configuration may help to explain the lack of fore‐arc basement and cover exposed in the suture zone marked by the Longitudinal Valley.

Terrane‐controlled crustal shear wave splitting in Taiwan

“…The LV is generally regarded as the arc‐continent suture zone whose shear can produce anisotropic mylonite zones that are shear zone parallel. If steeply dipping, this zone can produce the valley‐parallel patterns [e.g., Lewis et al , ]. Since arc rocks such as those found in the CR are primarily isotropic [e.g., Miller and Christensen , ], the observed splitting may be due to shear zones related to and subparallel to the collision zone.…”

“…An oblique thrust dipping under southern CR defines the suture with the Central Range orogen [ Lee et al , ]. The Longitudinal Valley (LV) is a deep alluvial basin generally regarded as the collisional suture [e.g., Lewis et al , ].…”

Geochemistry and Geochronology of the Accreted Mafic Rocks From the Hengchun Peninsula, Southern Taiwan: Origin and Tectonic Implications

“…Meanwhile, the Huatung‐Philippine Sea Plate began subducting beneath the Eurasian Plate toward the NW at a rate of 82 km/m.y. along the Ryukyu Trench (Lewis et al, ). Because the boundary between the oceanic and continental crust at the northern margin of the SCS trends differently from both the Manila Trench and the north Luzon arc (C. Y. Huang et al, ), the transition from intraoceanic subduction to continental subduction has migrated southward, and the orogenesis induced by oblique arc‐continent collision has propagated to the SSW at ~60 km/m.y.…”

“…Because the boundary between the oceanic and continental crust at the northern margin of the SCS trends differently from both the Manila Trench and the north Luzon arc (C. Y. Huang et al, ), the transition from intraoceanic subduction to continental subduction has migrated southward, and the orogenesis induced by oblique arc‐continent collision has propagated to the SSW at ~60 km/m.y. (C. Y. Huang et al, ; Lewis et al, ).…”

“…Meanwhile, the Huatung-Philippine Sea Plate began subducting beneath the Eurasian Plate toward the NW at a rate of 82 km/m.y. along the Ryukyu Trench (Lewis et al, 2015). Because the boundary between the oceanic and continental crust at the northern margin of the SCS trends differently from both the Manila Trench and the north Luzon arc (C. Y.…”