Empirical fragility curves for masonry houses using data from two earthquakes in Chile

Abstract

Chile is a country constantly affected by large-scale seismic events, among which are those that occurred in Valdivia 1960 (Mw=9.5) and Maule 2010 (Mw = 8.8). According to official Chilean records, the 2010 Maule earthquake caused damages in 370,051 houses. The possible consequences that future earthquakes may cause should be estimated using seismic risk concepts. Seismic risk can be defined as the material, economic and human losses due to the seismic hazard. To estimate the seismic risk, a seismic hazard, an exposure model and fragility curves need to be considered. Empirical fragility curves for reinforced masonry houses in Chile are determined in this study using data from the Iquique 2014 (Mw = 8.2), and Illapel 2015 (Mw = 8.4), earthquakes. The official cadastre of houses damaged during those earthquakes are used to estimate these fragility curves. The databases contain the damage states of 4,338 and 764 masonry houses for the 2014 and 2015 earthquakes, respectively. Peak ground acceleration values from shake maps estimated by the United States Geological Survey (USGS) are used as the intensity measure type (IMT) to express the ground shaking. The fragility curves are computed for four damage states (slight, moderate, extensive and complete) and for the two earthquakes by adjusting lognormal functions to the damaged houses data. The developed fragility curves are compared with those proposed by Hazus. As expected, the proposed fragility curves for reinforced masonry houses return better prediction of the damage for these earthquakes than the fragility curves available in Hazus.