GEOLOGICAL SOCIETY OF THE PHILIPPINES

DISTRIBUTION OF DEFORMATION ACROSS THE SUNDALAND/PHILIPPINE SEA PLATE BOUNDARY FROM GPS RESULTS AND TOMOGRAPHIC STUDIES

 

Rangin Claude, and Manuel Pubellier
CNRS and Laboratoire de Géologie, Ecole Normale Supérieure
24 rue Lhomond, 75231 Paris, France,
Paris France.


ABSTRACT

        Convergence between rigid Sundaland (SU) and the Philippine Sea plate (PH) is distributed across a 600 km-wide zone including in the Philippines the Sundaland stretched continental margin in Palawan/Borneo and the newly accreted exotic Island arc extending from Luzon to the Molucca Sea. GPS results indicate PH/SU convergence is mainly absorbed along main plate boundaries, but also within Sundaland where major sedimentary basins were developed. Excluding motion along the Philippine Fault, the balanced budgets of active shortening in the PMB shows the Luzon Visayas and Mindanao islands belong to rather rigid blocks.

        A new tomographic model built across the Philippine Mobile Belt was used to image the subducted slabs in the mantle, providing a guideline for the subduction history of the Philippines. When compared with the timing of the island arc volcanism related to these subductions in the Philippines, the tomographic images of the slabs help constrain average the finite motion along the main PMB convergent boundaries.

        The obtained velocities are then compared to the instantaneous rates of deformation provided by the GPS results of the GEODYSSEA (EC/ASEAN) project across the same plate boundaries. We discuss the fit that exists between the active convergence rates across the main trenches on both sides of the PMB, and the long term subduction velocities obtained from geologic data and tomographic images.

 
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