[S-IT20] New perspectives on accretion and exhumation processes during oblique plate convergence

[SIT20-P03] Oblique convergence in eastern Taiwan and the fate of the Luzon Arc illuminated by stress inversion: accretion and decoupling

*Ban-Yuan Kuo¹、Pei-Ru Jian¹ (1.Institute of Earth Sciences, Academia Sinica)

キーワード：Luzon arc, decoupling, stress inversion

The oblique plate convergence along eastern Taiwan suture zone results in Luzon Arc accretion and subduction. The associated complex deformation is difficult to visualize using conventional 2D stress analyses. We employed a 3D spatial clustering approach in eastern Taiwan to reveal how stress varies along the convergence plate boundary. Results show that the maximum horizontal compression orientation, SH, is parallel to the plate motion throughout the boundary at all depths except in the crust of the northern segment, where SH exhibits a clockwise rotation from convergence-parallel by up to 30 degrees. Concurrent with the SH rotation, the maximum compressive P-axes steepen in the same crustal segment. We interpret this systematic variation along the suture and with depth as resulting from the rotation of the stress regime in the crust of the Luzon Arc forced by the oblique subduction, and likely augmented by the bending of the Ryukyu Arc–Central Range continental sliver. The differential response with depth may signify an initial decoupling of the buoyant volcanic arc from the mantle lithosphere during early subduction. The bending of the Ryukyu Arc–Central Range continental sliver may also be illuminated by the seismogenic structure associated with the 2018-2022 Hualien earthquake sequence.