Towards Earthquake-resilient Buildings: Rupture Process & Exposure/Damage Analysis of the 2013 M7.1 Bohol Philippines Earthquake

Abstract

The strong ground shaking due to the Mw7.1 Bohol Philippines earthquake left a significant imprint on its built environment. Two key factors defining this event include the wide spread of seismic intensities inferred to have shaken the island and the extensive building damage. These make the Bohol Earthquake an important opportunity to improve knowledge on building fragility and vulnerability. However, this entails a statistical description of building damage and a reliable source model for accurate estimation of earthquake ground motion. To this end, an extensive survey was conducted leading to a robust description of over 25,000 damaged and undamaged structures. This comprehensive database represents a mix of construction types at various intensity levels, in both urban and rural settings. For the ground motion estimation, the geometry and slip distribution of the finite source models were based on the analysis of SAR data, aftershocks and tele-seismic waveforms. Ground motion fields were simulated and compared using two methods including the stochastic modeling and a suite of ground motion prediction equations. The intensity-converted ground motions were calibrated and associated with the exposure-damage database to derive the empirical fragility and vulnerability models for typical building types in Bohol. These newly-derived models were used to validate the building fragility and vulnerability models already in use in the Philippines.

This post-event assessment emphasizes the importance of assembling an exposure-damage database whenever damaging earthquakes occur. The sensitivity of fragility functions to ground motion inputs is also highlighted. Results indicate that the pattern of damage is best captured in the stochastic finite-fault simulation, although the Zhao et al. (2006) ground motion model registers a comparable range of ground motions. Constraints were placed on seismic building fragility and vulnerability models, which can promote more effective implementation of building regulations and construction practices as well as to deliver credible impact forecasts. Show more