Island Arc special Publication

"Recent deformation at the junction between the North Luzon block and the Central Philippines, from ERS-1 images"

M. Pubellier (1), F. Garcia (2) , A. Loevenbruck (1) , J. Chorowicz (2)

(1) : CNRS, UMR 8538, Laboratoire de Géologie, Ecole Normale Supérieure, 24 rue Lhomond 75231 Paris Cedex 05 France.

(2) : Département de Géotectonique, CNRS ESA 7072, T 26-16 E1, Université Pierre et Marie Curie, 4 Place Jussieu 75252 Paris France.

Abstract

The transfer of the major part of the motion between the Philippine Sea Plate and the Sunda block is accommodated along a NW shear wide zone partly on the Philippine Fault and partly on the Sibuyan Verde Passage Fault (SVPF) as indicated by GPS and geological data. Given the limited motion along the SVPF and the important motion along the Philippine Fault, as well as the necessity of a connection between these faults and the southern Manila Trench, a transtensional motion along the NE-SW Macolod Corridor may be predicted. We make use of SAR ERS-1 images to analyse the volcano-tectonic features of this area because these images are sensitive to minute textural or topographic contrasts resulting from small effects of recent deformation. In addition they allow to determine accurately the shape of the base of volcanic edifices and to detect linear clusters of very small adjascent cones (Chorowicz et al., 1997).

The results presented herein allow us to extend the features recognized earlier to a larger Macolod Corridor. Large faults actually connect the Philippine Fault to the Sibuyan Verde Passage Fault all accross the Taal Volcanic Field. In addition to extension along NE faults, we identify an important component of left-lateral strike-slip underlined by fault scarps, dykes, alignments of volcanoes and pull-apart basins, accompanied by extension along N-S faults. A relative chronology of the fractures and volcanic edifices is proposed. When compared to the existing ages of the volcanics, an evolution scheme of the area may be proposed, according to which extension shifted from a nearly N-S opening between 5 and 2 my to a direction close to E-W at Present. The early N-S extension existed in the Marinduque Basin and may have migrated northward and rotated to the present Macolod Corridor.