Earthquake Performance of Structures in the Philippines: A Post-event Assessment of the M7.2 October 2013 Bohol Earthquake

Abstract:

A M7.2 inland earthquake occurred in Bohol, Philippines on the 15th of October 2013, associated with rupture along a newly-discovered thrust fault called the North Bohol Fault. While secondary hazards including lateral spreading, landslides, sinkholes, liquefaction, coastal uplift and subsidence have been observed, the impact was dominated by strong ground shaking that killed about 230 people and damaged over 70,000 buildings. Because of the extensive damage and the wide spread of intensities inferred to have shaken the island, the Bohol earthquake presents an important opportunity to improve knowledge of building fragility for the Philippines and similar countries. To this end we undertook a statistical building survey of over 18,000 damaged and undamaged structures located in urban and rural settings and at various inferred ground motion intensity levels. Building typology developed by structural engineers in the Philippines has been considered in classifying the structures based on structural materials and era of construction. The vast majority of the buildings are residential houses with wall types made of wooden materials, concrete hollow blocks or confined masonry. Tailored to assess the vulnerability of structures to earthquake loadings, this post-event analysis aims to validate and constrain the building fragility curves for seismic risk assessment. This can lead to more robust impact forecasts and higher priorities on seismic regulations and construction practices, applicable not only in Bohol but in other areas in the Philippines as well.