No 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. According to paleoseismology studies and intensity maps, the earthquake source relates to the normal Ventas de Zafarraya Fault (Granada, Spain). Diverse studies registered and later analyzed hydrological effects, such as landslides, rockfalls, soil liquefaction, all-around surge and loss of springs, alterations in the phreatic level, discharge in springs and brooks and well levels, along with changes in physical and chemical parameters of groundwater. Further insight into these phenomena found an interplay between hydromechanical processes and crust surface deformations, conditions, and properties. This study focuses on analyzing and simulating the features involved in the major 1884 event and aims at elucidating the mechanisms concerning the mentioned effects. This ex-post analysis builds on the qualitative effects and visible alterations registered by historical studies. 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 hydromechanical features and the time evolution of the ground pore–pressure distribution in both the preseismic and coseismic stages, matching some of the shreds of evidence found by field studies. This procedure has helped to shed light on the causal mechanisms and better understand some parameters of this historical earthquake, such as its hypocenter and magnitude. This methodology can be applied to other events registered in the National Catalogues of Earthquakes to achieve a deeper insight, further knowledge, and a better understanding of past earthquakes.

The Pico de Navas landslide was a large-magnitude rotational movement, affecting 50x10 6 m 3 of hard to soft rocks. The objectives of this study were: (1) to characterize the landslide in terms of geology, geomorphological features and geotechnical parameters; and (2) to obtain an adequate geomechanical model to comprehensively explain its rupture, considering topographic, hydro-geological and geomechanical conditions.The rupture surface crossed, from top to bottom: (a) more than 200 m of limestone and clay units of the Upper Cretaceous, affected by faults; and (b) the Albian unit of Utrillas facies composed of silty sand with clay (Kaolinite) of the Lower Cretaceous.This sand played an important role in the basal failure of the slide due to the influence of fine particles (silt and clay), which comprised on average more than 70% of the sand, and the high content presence of kaolinite (>40%) in some beds. Its microstructure consists of accumulations of kaolinite crystals stuck to terrigenous grains, making clayey peds. We hypothesize that the presence of these aggregates was the internal cause of fluidification of this layer once wet. Besides the faulted structure of the massif, was an important factor for the occurred landslide. Other conditioning factors of the movement were: the large load of the upper limestone layers; high water table levels; high water pore pressure; and the loss of strength due to wet conditions. The numerical simulation of the stability conditions concurs with our hypothesis. The landslide occurred in the Recent or Middle Holocene, certainly before at least 500 BC and possibly during a wet climate period. Today, it appears to be inactive.Due to mineralogical features of involved material, facies Utrillas, in the landslide, the study helps to understand the frequent slope instabilities all along the Iberian Range where this facies is present.Keywords: deslizamiento rotacional, Cordillera Ibérica, facies Utrillas, Cretácico, simulación numérica Resumen El deslizamiento de Pico de Navas fue un movimiento rotacional de gran magnitud, que involucró 50x10 6 m 3 de rocas. Los objetivos de este trabajo han sido: (1) caracterizar el deslizamiento a partir de la Geología, los elementos geomorfológicos y los parámetros geotécnicos; y (2) obtener un modelo geomecánico que permita explicar adecuadamente la rotura, teniendo en cuenta la topografía, previa y posterior al movimiento, y las condiciones hidrogeológicas y geomecánicas.La superficie de rotura atravesó, de arriba abajo: a) 200 m de calizas y arcillas del Cretácico superior, afectadas a su vez por fallas, y b) la unidad del Albense de facies Utrillas, compuesta de arenas limosas con arcilla (caolinita) del Cretácico Inferior. Las facies Utrillas tuvieron un papel importante en la rotura basal del deslizamiento debido a la influencia de las partículas finas (limos y arcillas) que alcanzan el 70% de media y el alto contenido en caolinita, >40% en algunos niveles. Tienen una microestructura particular: al microscopio electrónico se ven p...

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 paleoseismology studies and intensity maps, the earthquake source relates to the nor-mal Ventas de Zafarraya Fault (Granada, Spain). Diverse studies registered and later analyzed hydrological effects, such as landslides, rockfalls, soil liquefaction, all-around surge and loss of springs, alterations 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 be-tween hydro-geomechanical processes and crust surface deformations, conditions, and properties. This study focuses on analyzing and simulating the features involved in the major 1884 event and aims at elucidating the mechanisms concerning the mentioned effects. This ex-post analysis builds on the qualitative effects and visible alterations registered by historical studies. 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 hy-dro-geomechanical features and the time evolution of the ground pore-pressure distribution in both the preseismic and coseismic stages, matching some of the shreds of evidence found by field studies. This methodology can be applied to other events registered in the National Catalogues of Earth-quakes to achieve a deeper insight, further knowledge, and a better understanding of past earth-quakes.

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.