Mapping Philippine Vulnerability to Environmental Disasters

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Geophysical factors also transcend or go beyond administrative boundaries yet vulnerability to these types of disasters may be estimated according to seismic zones and/ or at the provincial level.

RISK TO EARTHQUAKES

Since 1968, PHIVOLCS has recorded twelve destructive earthquakes in the Philippines. This record includes the infamous July 16,1990 Luzon earthquake which caused innumerable injuries and at least 1,100 deaths. Seismicity (geographic and historical distribution of earthquake events) is all over the country except in the Palawan region.

Risk to Earthquakes

Risk to Earthquakes

The top ten provinces that are at risk to earthquakes are:

  1. Surigao Del Sur
  2. La Union
  3. Benguet
  4. Pangasinan
  5. Pampanga
  6. Tarlac
  7. Ifugao
  8. Davao Oriental
  9. Nueva Vizcaya
  10. Nueva Ecija

La Union and Pangasinan are prone to earthquakes, especially the deep-focused ones, due to the Manila Trench while Surigao del Sur and Davao Oriental have earthquake hazards due to Philippine Trench and nearby active faults. Frequency of shallow and left-lateral strike-slip earthquakes in Nueva Vizcaya, Nueva Ecija, Eastern Pangasinan, Benguet and La Union can be attributed to its location along the Philippine Fault Zone.

However, Ifugao, despite having less earthquake occurrences is at risk because of its very high vulnerability to disasters.

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RISK TO EARTHQUAKE-INDUCED LANDSLIDES

Risk to Earthquake-Induced Shallow Landslides

Risk to Earthquake-Induced Shallow Landslides

Most of the provinces, except Palawan, are susceptible to landslide hazards. The top ten provinces that are at risk to earthquake-induced shallow landslides are:

  1. Ifugao
  2. Lanao Del Sur
  3. Sarangani
  4. Benguet
  5. Mountain Province
  6. Bukidnon
  7. Aurora
  8. Davao del Sur
  9. Davao Oriental
  10. Rizal

Ifugao, Lanao del Sur and Sarangani ranked high because of their high vulnerability to disasters while Rizal ranked the lowest. Benguet, despite its low vulnerability, ranked four because of its high exposure factor or population density. Aurora ranked higher than Davao del Sur and Davao Oriental despite its low vulnerability compared with the other two provinces. This is due to the fact that the whole of Aurora is more susceptible to landslide than the other two provinces.

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RISK TO VOLCANIC ERUPTIONS

Philippines lies within the Ring of Fire, a region of subduction zone volcanism surrounding the Pacific Ocean. This explains the distribution of most volcanoes in the Philippines. In 1991, Mt. Pinatubo eruption was well known to be the most violent eruption in the 20th century. Philippine Volcanoes are classified as Active, Inactive and Potentially active. Twenty-two (22) historically active volcanoes are distributed all over the archipelago.

Risk to Volcanic Eruptions

Risk to Volcanic Eruptions

Since volcanoes are not present in some provinces, these particular areas have no risk to volcanic eruptions. The top ten provinces at risk are:

  1. Camiguin
  2. Sulu
  3. Biliran
  4. Albay
  5. Bataan
  6. Sorsogon
  7. South Cotabato
  8. Laguna
  9. Camarines Sur
  10. Batanes

Camiguin has the highest risk because the land area is so small such that a volcanic eruption can affect the whole province. Sulu ranked second because it has the most number of active and potentially active volcanoes.

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RISK TO TSUNAMIS

In November 14,1994, a 7.1 magnitude earthquake in Mindoro triggered a tsunami that left at least 41 persons dead, mostly children and old people.

Risk to Tsunamis

Risk to Tsunamis

Most of the coastal areas have experienced a tsunami or have a tsunami hazard potential. The top ten provinces that are at risk to tsunamis are:

  1. Sulu
  2. Tawi-tawi
  3. Basilan
  4. Batanes
  5. Guimaras
  6. Romblon
  7. Siquijor
  8. Surigao del Norte
  9. Camiguin
  10. Masbate.

Sulu and Tawi-tawi took the top two seats because of their high potential for tsunami owing to their location between two nearby trenches namely, Sulu Trench and Cotabato Trench. Moreover, both provinces are also densely populated and have very high vulnerability. Similarly, most areas in Basilan and Romblon are at high risk especially because they have been previously affected by a tsunami. (PHIVOLCS)

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COMBINED RISK TO GEOPHYSICAL DISASTERS

The composite risk map of all geophysical hazards under consideration is shown below:

Combined Risk to Geophysical Disasters

Combined Risk to Geophysical Disasters

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