Seismic Risk Analysis of Urban Non-engineered Buildings: Application to an Informal Settlement in Mérida, Venezuela

Seismic risk scenarios are obtained for an informal settlement in Mérida (Venezuela), which is representative of an important number of urban areas in earthquake-prone regions of the developing world. The vulnerability indices of the buildings range between 0.64 and 0.80 on a scale of 0 to 1. In an intensity IX earthquake scenario, more than 32% of the buildings would suffer damage of grade 4 (extensive) or greater. A structural analysis of the buildings in the study area shows that they are unsafe for gravity loads, and that the seismic demands exceed the strength of the constructions. Simple and comparatively inexpensive measures can improve the seismic performance of these buildings; the vulnerability can be reduced by about 51%. In an intensity IX earthquake scenario the expected economic loss before retrofitting the buildings is US$5.36 million, with 275 fatalities; once retrofit has been carried out, the resulting figures are US$0.39 million and 10 fatalities. Retrofit would cost US$1.04 million, whereas reconstruction would cost US$19 million.