Mindoro, Philippines

2015-01-12 08:47:14

Mindoro Island is located where the Palawan Continental Block indented into the Philippine Mobile Belt during the Early Miocene and where the Manila Trench terminates, having ceased convergence due to collision. The seismotectonics ofMindoro are crucial to understanding the processes of arc-continent collision and slab dynamic responses of convergence cessation. This study was conducted using data from both the EHB and Global Centroid Moment Tensor catalogues. It is shown that following the southeasterly reduction of convergence rates from the Manila Trench offshore NWMindoro to onshore SWMindoro, the slab dipping angles steepen, were initiated at depth (~200 km) and propagate upwards. The horizontal distances of the trench and slab, as measured from the Wadati–Benioff zone at 200 km depth, also reduce in a southeasterly direction. Observations of intermediate-depth earthquakes that exhibit predominantly down-dip extensional stress patterns attest that the steepening of slab dipping angles is due to the negative buoyancy of the slab. In contrast, a broad region covered by central and south Mindoro, the Romblon group, and NWPanay, is characterized by a sporadic distribution of shallowearthquakes of mostly strike-slip type. Among these, the significantly sized events (Mw N 5.5) tend to distribute around the borders suggesting that the region roughly acts as a unit block, moving or rotating coherently. Events in the vicinity of theWawa–Mamburao valley exhibiting normal faulting of NW–SE horizontal extension suggest rifting of the Macolod Corridor extending southwestward to NWMindoro.

附件1: Paper