Numerical Simulation and Characterization of the Hydrogeomechanical Alterations at the Zafarraya Fault Due to the 1884 Andalusia (Spain) Earthquake

Abstract

The 1884 Andalusia Earthquake, with an estimated Magnitude between 6.2 and 6.7, is one of the most destructive events that shook the Iberian Peninsula, causing around 1200 casualties. Ac-cording to both paleoseismology studies and intensity maps, the earthquake source relates to the normal Ventas de Zafarraya Fault (Granada, Spain). Diverse hydrological effects were registered and later studied: landslides, rockfalls, soil liquefaction, all-around surge and loss of springs, alter-ations in the phreatic level, discharge in springs and brooks, and well levels, along with changes in water properties. Further insight into these phenomena found an interplay between hy-dro-geomechanical processes and crust surface deformations, conditions, and properties. This study focuses on simulating the features involved by the major 1884 event and aims at elucidating the mechanisms concerning the mentioned effects. It encompasses conceptual geological and kinematic models, and a 2D finite element simulation to account for the processes undergone by the Zafarraya Fault. The study focuses on the variability of hydro-geomechanical features and the time evolution of the ground pore-pressure distribution in both the preseismic and coseismic stag-es, matching some of the shreds of evidence found by field studies. This methodology can be ap-plied to other events registered in the National Catalogues of Earthquakes to reach a deeper in-sight, further knowledge, and better understanding of past earthquakes.