Active tectonics in Sabah – seismicity and active faults

Abstract

The location of Sabah near the boundaries of three major tectonic plates, the Eurasian, India-Australia and Philippine-Pacific plates, makes it prone to seismic activities. Sabah is currently under a WNW-ESE compressive stress regime due to the effect of plate movements as the Philippine-Pacific plate move westward at the rate of about 10 cm/ year against the southeast moving Eurasian plate at the rate of about 5 cm/year. The WNW-ESE compression is being accommodated by NE-SW trending active thrust faults and NW-SE trending active strike-slip faults present all over Sabah. Evidence of active faults based on geomorphological features, such as linear structures associated with triangular facets, stream offsets, mud volcanoes and hot springs are widespread in Sabah.The WNW-ESE compression resulted in regional folding or warping of the upper crust to produce an uplifted belt trending NE-SW in Western Sabah, currently occupied by the Crocker-Trusmadi Range. The warping and uplift of the upper crust is thought to be driving extensional tectonics, marked by the presence of NE-SW trending active normal faults along the crest and flanks of the Crocker-Trusmadi Range anticlinorium. At least six elongate Quaternary graben-like basins (Tenom, Keningau, Tambunan, Ranau, Timbua and Marak-Parak) occur along the crest of the anticlinorium.