3-D plate interactions in central Taiwan: Insight from flexure and sandbox modeling

We have conducted flexure and sandbox experiments to investigate the 3-D plate interactions in Central Taiwan. The abnormally low-surface-slope mountain belt in Central Taiwan fails to account for the large deflection of the underlying lithosphere. We propose that the northward subduction of the Philippine Sea Plate applies additional bending moments and shear forces to the Eurasian Plate at the plate suture. The interactions between the Eurasian Plate and the Philippine Sea Plate in Central Taiwan could have enhanced the deflection of the continental margin and created a deep tear fault identified in an early study. We have conducted flexure and gravity modeling to confirm that additional downward shear forces are exerted on the Eurasian Plate along the suture zone of the two plates. These forces increase northwardly with the subduction of the Philippine Sea Plate. The fact that the Eurasian Plate deflects with the northward bending of the Philippine Sea Plate implies an eastward subduction of the Eurasian Plate in Central Taiwan. In addition, our model suggests that the bending moment changes from positive (bending upward) to negative (bending downward) southwardly along the Longitudinal Valley. This finding implies a transition from a continental crust to an oceanic one or to a transitional crust southward along the plate suture or/and delamination of a light crust during subduction of the southern part of the Eurasian Plate. The spatial variation in bending moment along the plate suture could also result from a break-off of the east leading edge of the Eurasian Plate near the northern end of the Longitudinal Valley.We have also investigated surface structure by incorporating oblique deflection of the continental margin into our sandbox model. Unlike previous extrusion models, our results show that a salient structure with low-surface-slope mountain ranges can develop even without the presence of a rigid basement high.

Research highlights
► Plate interactions in Central Taiwan are simulated by flexure and sandbox modeling.
► Shear force increases northwardly with the subduction of the Philippine Sea Plate.
► Bending moment increases southwardly along the plate suture.
► A salient structure can develop above an obliquely bending decollement.