The 1884 Andalusian earthquake, Spain: re-evaluation of seismic intensities and source determination

Abstract

In this work, we present a quantified model of the seismic source for the 1884 Andalusian earthquake (Granada, Spain) that accounts for the dimensions and orientation of the rupture, average slip, focal depth, magnitude, and scalar seismic moment. We undertook archival research to find additional accounts, increasing the number of intensity data points from 157 to 213, which has allowed for a more detailed distribution of European Macroseismic Scale 1998 intensities. The re-evaluated intensity values were converted into peak ground acceleration (PGA) values using an empirical relation and then modeled using rectangular fault models with regular slip and different fault sizes, depths, and geometries. We have used two different approaches to carry out the comparison between synthetic and observed PGAs. The best results correspond to a normal fault with strikes of 270°–330° that steeply dips to the north, with the northern block moving down, and a shallow focus. This geometry agrees with that of the Ventas de Zafarraya fault system, which was proposed by different authors as the origin of the 1884 earthquake.