Mount Mayon is located in Legazpi City, province of Albay, in the Philippines (see upper right). Coordinates: 13º 16'N and 123º 41'E. It is in the Bicol Volcanic Chain, which includes the 5 provinces (11 large islandes) south-east of Japan. The Bicol Chain rests on a basin which overlays a plethora of folded sedimentary rocks from the Eurasian and Pacific Plates.
The Philippine Fault Zone decouples the northwestward motion of the Pacific with the southwestward motion of the Eurasian Plate. The Eurasian Plate subducts into the western side of Luzon and Mindoro at 3cm/year, but it's the movements along other active faults are responsible for the present-day high seismicity of the Philippine Archipelago.
Figure 3.
This diagram shows the four tectonic plates which surround and squeeze the Philippine Plate.
Mayon is located not only within a volcanic chain, but it is also near the center of the Philippine Fault Zone (PFZ). This zone contains a bundle of parallel to sub-parallel active faults trending NNW and SSW, and is important because it has broken up the Philippine Plate into many micro-plates. Mayon is located on the boundary of one of these micro-plates, which could account for much of the activity. This region also holds the Philippine trench, which marks the position of a subduction zone along the eastern side of Mayon. This active zone produces earthquakes approximately 80km deep, and plays a large role in the creation of the hotspot that is the Philippines. Figure 4. In this figure, the teeth indicate the over-riding plate. The black teeth mean that the area is an active subduction zone, while the white teeth specify an area which is now a passive subduction zone. The arrows point in the direction of movement along the various transform faults found within the Philippine Plate. |
Figure 5. Graphic of a releasing bend in a left-lateral strike-slip fault. Left-lateral strike-slip movement generates transtensional fault splays. The figure is from Lagmay (2005).
Below is a geologic map of Mount Mayon:
Below is a geologic map of Mount Mayon: