Collision Complexities in Palawan-Mindoro-Panay: New Insights from GPS and Recent Earthquakes

Mario A. Aurelio^(1,2) and Corné Kreemer⁽³⁾

⁽¹⁾ Lands Geological Survey Division, Mines and Geosciences Bureau,Quezon City, Philippines
⁽²⁾ Mapua Institute of Technology, Manila, Philippines
⁽³⁾ Collège de France, Aix en Provence, France

Abstract

Earlier models of plate interaction between the continental fragment of northern Palawan (NPB), believed to have been derived by rifting from mainland Asia in mid-Neogene times, and the western margin of the Philippine Mobile Belt (PMB), have been developed within the context of straight-forward collisional tectonics involving a buoyant continental mass and a hot volcanic arc. Among the consequent structures modeled are shallow thrust zones that produce shallow focus earthquakes. Frontal interaction between these blocks would manifest in terms of plate motions that are oriented perpendicularly to the collision boundaries.

While such scenarios could have been prevalent at the initial stages of collision (around 16 Ma), recent data (0 Ma) from GPS and earthquakes in the Palawan-Mindoro-Panay (PMP) region suggest that the present-day plate interaction between the NPB and PMB is characterized by processes which are more complex than those expected from a classical collision zone. Plate interaction in the PMP region occurs obliquely, generating transpressive structures manifested as thrust-strike-slip systems that develop far into the PMB. Persistent deep earthquakes indicate a steeply-dipping crust underneath the collision zone, causing a gravitational pull on the NPB. Contemporaneously, the NPB continues to deform sidewards (by buckling? and overthrusting) against the PMB.

Denser and finer GPS and seismic networks are necessary to further understand better these complex collision processes.