| dc.description.abstract | The tightly curved Banda Arc (eastern Indonesia) plays a pivotal role in the convergent interaction of the Eurasian, Australian, and Pacific plates. Historically there have been two opposing hypotheses regarding its origin: either the arc has been formed by two opposite-dipping subduction zones joining at the apex, or a single slab has been wrought in its current position by surface kinematics and mantle processes. Using detailed tectonic reconstructions and mantle tomography, the latter view has recently gained substantial support by the work of Spakman and Hall (2010). Through numerical modelling of the instantaneous dynamics of the intricate subducting system, the research presented here aims to determine the factors that control the evolution of the single slab, but also to provide insight into the complexities of instantaneous numerical modelling of subduction in general. To aid the construction of very complex model geometries, we have developed a tool that allows us to digitally draw faults, slab sections, and plate outlines based on tomography, surface topography, and Wadati-Benioff zone geometry. The tool communicates with the finite element mesh generator, which then gives a composite mesh with highly desirable properties. Our results give a basic one-slab-model that satisfies both the predictions of the Spakman and Hall model and the stress state from CMT solutions and seismic fast directions. Better agreement can be attained by varying the buoyancy structure, to which the behavior of the model is found to be rather sensitive. Additionally, we propose that a mantle flow component is required in order to maintain the northern slab limb in the case that it has detached from the surface lithosphere. In the absence of flow-induced resistance, our results suggests that further convergent motion can effect a transition towards large-scale slab detachment progressing southward if there is little buoyant support at the d660 phase transition. | |
