Analogue Modeling of the Philippine Fault Bend


Cielo F. Bastero and Alfredo Mahar Francisco A. Lagmay

National Institute of Geological Sciences, College of Science,
University of the Philippines, Diliman, Quezon City 1101 Philippines




The Philippines is traversed along its length by a 1200 km fault zone, which is a result of the accommodation of stress created by the accumulation of oblique convergence between the Philippine Sea Plate and the Philippine archipelago. Analog models were made to simulate the movement of the left-lateral Philippine Fault along the bend of its central segment. The aim was to view features that result from the movement along this bend and to compare them with known tectonic and physiographic features of the Philippines. The modelling results indicate that ma- jor left-lateral faults splaying from the Philippine Fault (e.g. Legaspi, San Miguel, Verde Island, and Sibuyan Sea Faults) near its central segment can be reasonably explained by movement along a strike-slip bend. These fault splays generate major graben-forming structures and border several of the major basins of the Philippines. Another feature evident from analog models is the presence of a lens-shaped basin, which grows larger with continuous movement along the strike-slip bend. This is re- markably comparable to the lens-shaped basin (approximately 163,500 km2) found at the central part of the Philippine archipelago. Other aspects of Philippine tectonics such as subsidence, distribution of volcanic arcs and earthquakes and contemporary stress directions may be viewed in new light. The analog model of the Philippine Fault bend offers insights and a novel framework that can be tested in the field and used to interpret large-scale tectonics in the Philippines.


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