1. A computer system for determining a damage index indicative of the damage caused by an earthquake to a portfolio of objects associated with a geographical area, the system comprising: means for storing local portfolio replacement value indices assigned to coordinates of the geographical area; means for receiving and storing location, depth and magnitude data associated with the earthquake; means for calculating a local damage index for each coordinate having a local portfolio replacement value index assigned to it, the local damage index being calculated from the location, depth and magnitude data and from the local portfolio replacement value index; and means for calculating the damage index by aggregating the local damage indices for the coordinates.