Philippine Fault System

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The Philippine Fault System is an inter-related system of faults throughout the whole of the Philippine Archipelago,[1] primarily caused by tectonic forces compressing the Philippines into what geophysicists call the Philippine Mobile Belt.[2]

Philippine Mobile Belt

The Philippine Mobile Belt is composed of a large number of accretionary blocks and strips. Most strips are long and narrow like the Zambales ophiolites which is at least 400 km long and 50 km wide. The strips generally run north-south and the zones of convergence are usually demarcated by fault lines. The Philippine Mobile Belt is compressed on the west by the Eurasian Plate and two arms of the Sunda Plate, and on the east by the Philippine Sea Plate. These tectonic plates have compressed and lifted parts of the Philippines causing extensive faulting, primarily on a north-south axis. All faults in the Philippines are inter-related by the tectonic forces of the Philippine Mobile Belt, or its tectonic induced volcanism. A more complete understanding can be gained by viewing the faults in the Philippines as an inter-related Philippine Fault System.

Philippine Fault

The main fault runs most of the length of the Philippines and is called the Philippine Fault. It extends from Davao Gulf in the south, bisects the Caraga region at the Agusan River basin, crosses to Leyte and Masbate islands, and traverses Quezon province in eastern Luzon before passing through Nueva Ecija up to the Ilocos region in northwest Luzon. Here, the fault has become braided and is no longer single. The Philippine Fault, probably active since the Middle Miocene is a recent example of the north-south strike-slip fault zones of Luzon. The N150°E segment, which breaks the meridian continuity of the Philippine Fault system in Luzon, is located to the west of Benham Plateau on the western edge of the Philippine Sea Plate. The N150°E fault probably has a recent genesis and could be a mechanism to absorb backwards the convergence between Benham Plateau and the east Luzon arc.[3]

Following the major 1990 Luzon earthquake, scientists reconsidered their fault models and following the lead of Pinet and Stephan (1989), thought it likely that Benham Plateau is still displacing central Luzon and the Philippine Fault System to the west, and so caused the 1990 Luzon earthquake. The 20 second or 50 second wave in the 1990 quake developed a new east-west sub-fault, which terminated disastrously at Baguio.

Gallery

  • Tectonic Map of Far Northern Philippines including the Philippine Fault System

  • Tectonic Map of Northern Central Philippines including the Philippine Fault System

  • Tectonic Map of Central Philippines including the Philippine Fault System

  • Tectonic Map of Southern Philippines including the Philippine Fault System

  • Tectonic Map of Far Southern Philippines including the Philippine Fault System

  • Tectonic diagram of the Philippines, showing Philippine Fault System generally

  • Diagram of Northern and central sections of the Philippine Fault System

  • Diagram of Northwest Luzon section of Philippine Fault System

See also

References

  1. ↑ Nicolas Pinet and Jean Francois Stephan (1989) in Tectonics of Circum-Pacific Continental Margins ISBN 90-6764-132-4 p170
  2. ↑ Rangin and Pubellier (1990) in Tectonics of Circum-Pacific Continental Margins ISBN 90-6764-132-4 p140 ff
  3. ↑ Nicolas Pinet and Jean Francois Stephan (1989) in Tectonics of Circum-Pacific Continental Margins ISBN 90-6764-132-4 p.179

External links


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