1. A computer system for determining a regional impact of earthquake events, the system comprising: means for associating each geographical region from a set of defined geographical regions with a group of reference measuring stations selected from a plurality of seismological measuring stations distributed in the respective geographical region; a data capturing module configured to receive from the reference measuring stations, for an earthquake event, instrumental intensity values indicative of a local strength of seismic motion; and an indexing module configured to determine earthquake indices indicative of the regional impact of the earthquake event, the earthquake indices including at least a regional index for each of the geographical regions, each regional index being determined from the instrumental intensity values received from the reference measuring stations associated with the respective geographical region, and each of the instrumental intensity values being weighted with a weighting factor assigned to the reference measuring station having provided the instrumental intensity value.