1. A computer system for determining an impact index indicative of impact or damage caused by an earthquake to a portfolio of values or objects associated with different geographical locations, the system comprising: at least one hardware processor; means for storing an equation defined for calculating for a geographical location a local earthquake intensity based on a given distance of the geographical location from a hypocenter of an earthquake, and a given earthquake magnitude of the earthquake; at least one impact ratio table for storing for the geographical locations in each case impact ratios for different earthquake intensity levels; a portfolio data store including geographical locations and individual weighting factors assigned to the geographical locations, wherein the weighting factors are indicative in each case of a nominal value associated with the geographical location, the impact ratios weighted by the weighting factors are indicative in each case of a nominal loss at a geographical location, the impact index is indicative of a total nominal event loss, and the portfolio data store further includes a minimum total nominal event loss and a maximum total nominal event loss for a portfolio; an intensity calculation module, implemented by the at least one hardware processor, configured to calculate geometric distances of the geographical locations from a hypocenter of an earthquake event, and to calculate local intensity values for the geographical locations by applying in each case the equation to the magnitude of the earthquake event and the geometric distance of the respective geographical location from the hypocenter; and an index calculation module, implemented by the at least one hardware processor, configured to calculate the impact index for the geographical locations by determining in each case from the impact ratio table the impact ratio for the local intensity at the respective geographical location, and adding up the impact ratios weighted in each case by the weighting factor assigned to the respective geographical location, and further configured to calculate an event loss factor as a ratio of an event loss exceeding the minimum total nominal event loss, but not exceeding the maximum total nominal event loss, and a difference of the maximum total nominal event loss and the minimum total nominal event loss.