Estimating Earthquake Risks: The Use of Rapid Earthquake Damage Assessment System (REDAS) in the Province of Pangasinan, Philippines

Abstract

The Philippines has 18 regions and Pangasinan is the biggest province in Region I with a land area of
536,819 hectares. It has high risk to earthquakes due to the Manila Trench. This study was conducted to estimate
earthquake risk in the province with the use of Rapid Earthquake Damage Assessment System (REDAS) software. There
were three barangays from Binmaley, one of the 44 towns in the province, where actual building survey was taken to
represent residential, commercial, and mixed commercial and residential sites which were used in creating the
Pangasinan data base for this study. Estimation of earthquake risk using REDAS was based on the 1796 historical earthquake event which had a magnitude of 6.9 and a depth of 35 km. Results show that the total estimated floor area damages in square meters were 5,902,337 and 272,064 for complete damage with no collapse, and complete damage with collapse. Based on number of buildings, the total estimated complete with no collapse and complete with collapse damages were 115,694 and 5,315,
respectively. The total estimated economic loss in millions is 63,069. The number of injuries is 52,382 minor injuries,
10,949 serious injuries, 459 very serious injuries and 1,321 fatalities. The overall result show that the cities of Dagupan,
Urdaneta and San Carlos and the towns of Mangaldan, Malasiqui and Calasiao are the most at risk based on estimated
damage in terms of area in square meters, number of buildings, economic loss, number of injuries and fatalities. Results of the study have shown that REDAS is a valuable tool to estimate the extent of damages from an earthquake. Information from the estimated extent of damages in particular areas in the province can guide those who are involved in disaster risk reduction planning and implementation.