Methods, systems, and computer programs are presented for estimating the differences, due to building retrofitting, in damage caused to a building by an earthquake. One method includes operations for accessing a database to retrieve current fragility functions for predicting structural damage to a building, and for identifying features of the building. The method further includes operations for identifying a retrofit measure having a cost to improve the building structure, and for estimating a first building damage after a simulated earthquake utilizing a machine-learning program and the current fragility functions. The method further includes operations for determining new fragility functions for the building based on the retrofit measure and the current fragility functions, for estimating a second building damage after the simulated earthquake utilizing the new fragility functions, and for determining the difference in damage resulting from the retrofit measure based on the first and the second building damage.