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This work is focused on the Almonte-Marismas aquifer located within Doñana Natural Space (SW Spain); this aquifer is threatened by droughts, irrigation-driven groundwater overexploitation, urban use, and the potential reactivation of gas extraction and storage projects. We present ground deformation measurements from Sentinel-1 Interferometric Synthetic Aperture Radar (InSAR) data ranging from 1 to 2.5 cm, covering ∼2,500 km2 from 2014 to 2020. Detecting spatially distributed ground deformation over this agricultural area is challenging due to the low-coherence radar signals; consequently, the ground movement results are on the same order of magnitude as the errors associated with InSAR data. We have approached this issue by considering auxiliary information such as groundwater levels, climatic time series, and pumping rates and analyzing their spatio-temporal connections to ground displacements. We correlate InSAR and hydrogeological information through wavelet analysis, developing a Python package that allows applying the same methodology in other similar study areas. For the first time in the Doñana area, a significant relationship between distances to pumping wells and the displacement extent is detected. Moreover, other subsidence-related triggering factors are identified, such as the soil moisture balance, clay shrinking-swelling processes, and creep of geological formations. These results are highly valuable to support aquifer management decisions in the Doñana Natural Space; in this border region, three groundwater bodies were officially declared overexploited in 2020. Our findings provide a ground motion baseline assessment to help differentiate historical variations from any future anthropogenic effect in this complex marsh land ecosystem., National Youth Guarantee System, Tripartite Foundation for Training in Employment, Youth Employment Initiative (YEI), European Social Fund (ESF), European Union, Ministry of Ciencia e Innovación, IGME-CSIC, Depto. de Geodinámica, Estratigrafía y Paleontología, Fac. de Ciencias Geológicas, TRUE, pub

[EN] The El Salvador Fault Zone (ESFZ) comprises a set of a strike-slip faults, extending through the Central American Volcanic Arc within El Salvador, where the Cocos plate subducts under the Caribbean plate. These structures act as a boundary between the forearc sliver and the western margin of the Chortís block, accommodating the relative movement between them. The ESFZ has been responsible for several shallow, destructive earthquakes in El Salvador, thus posing a serious threat for millions of inhabitants. Understanding its seismic potential and the behaviour of its different segments results of great importance for the assessment and mitigation of seismic risk in the region. Geodetic techniques, such as GNSS and InSAR, are useful tools for measuring surface deformation related to tectonic activity. We are in the process of updating and densifying the existing GNSS velocity field in El Salvador, aiming to characterise the individual faults in the region by determining their slip rates and locking depth. Additionally, we will process InSAR data, trying to obtain a continuous measurement of the interseismic deformation. The combination of this information with other data (e.g. seismological and geological) through kinematic models will allow us to better understand the factors controlling the seismogenic behaviour of the ESFZ faults, evaluate their seismic potential and improve the seismic hazard assessment., [ES] La Zona de Falla de El Salvador (ESFZ) comprende un conjunto de fallas de deslizamiento extendiéndose a través del Arco Volcánico Centroamericano en El Salvador, donde la placa del Coco subduce bajo la placa Caribe. Estas estructuras actúan como límite entre el antearco volcánico y el margen occidental del bloque Chortís, acomodando el movimiento relativo entre ambos. La ESFZ ha sido responsable de varios terremotos someros destructivos en El Salvador, lo que representa una seria amenaza para millones de habitantes. Comprender su potencial sísmico y el comportamiento de sus diferentes segmentos resulta de gran importancia para la evaluación y mitigación del riesgo sísmico en la región. Las técnicas geodésicas, como GNSS e InSAR, son herramientas útiles para medir la deformación de la superficie relacionada con la actividad tectónica. Actualmente estamos actualizando y densificando el campo de velocidad GNSS existente en El Salvador, con el objetivo de caracterizar las fallas individuales en la región, determinando sus tasas de deslizamiento y profundidad de bloqueo. Además, procesaremos datos InSAR, tratando de obtener una medición continua de la deformación intersísmica. La combinación de esta información con otros datos (por ejemplo, sismológicos y geológicos) a través de modelos cinemáticos nos permitirá comprender mejor los factores que controlan el comportamiento sismogénico de las fallas de ESFZ, evaluar su potencial sísmico y mejorar la evaluación de la amenaza sísmica.

Different kinematic models have been proposed for the triple junction between the North American, Cocos and Caribbean plates. The two most commonly accepted hypotheses on its driving mechanism are (a) the North American drag of the forearc and (b) the Cocos Ridge subduction push. We present an updated GPS velocity field which is analyzed together with earthquake focal mechanisms and regional relief. The two hypotheses have been used to make kinematic predictions that are tested against the available data. An obliquity analysis is also presented to discuss the potential role of slip partitioning as driving mechanism. The North American drag model presents a better fit to the observations, although the Cocos Ridge push model explains the data in Costa Rica and Southern Nicaragua. Both mechanisms must be active, being the driving of the Central American forearc towards the NW analogous to a push-pull train. The forearc sliver moves towards the west-northwest at a rate of 12–14 mm/yr, being pinned to the North American plate in Chiapas and western Guatemala, where the strike-slip motion on the volcanic arc must be very small., Ministerio de Economía y Competitividad (MINECO), Depto. de Geodinámica, Estratigrafía y Paleontología, Fac. de Ciencias Geológicas, TRUE, pub

It has long been recognized that earthquakes change the stress in the upper crust around the fault rupture and can influence the behaviour of neighbouring faults and volcanoes. Rapid estimates of these stress changes can provide the authorities managing the post-disaster situation with valuable data to identify and monitor potential threads and to update the estimates of seismic and volcanic hazard in a region. Here we propose a methodology to evaluate the potential influence of an earthquake on nearby faults and volcanoes and create easy-to-understand maps for decision-making support after large earthquakes. We apply this methodology to the Mw 7.8, 2016 Ecuador earthquake. Using Sentinel-1 Interferometric Synthetic Aperture Radar (InSAR) and continuous GPS data, we measure the coseismic ground deformation and estimate the distribution of slip over the fault rupture. We also build an alternative source model using the Global Centroid Moment Tensor (CMT) solution. Then we use these models to evaluate changes of static stress on the surrounding faults and volcanoes and produce maps of potentially activated faults and volcanoes. We found, in general, good agreement between our maps and the seismic and volcanic events that occurred after the Pedernales earthquake. We discuss the potential and limitations of the methodology., European Commission, Directorate-General Humanitarian Aid and Civil Protection, Ministerio de Economía y Competitividad (MINECO), Depto. de Geodinámica, Estratigrafía y Paleontología, Fac. de Ciencias Geológicas, TRUE, pub

Ground subsidence is a critical problem in populated areas, which requires attention and routine monitoring. Specifically, subsidence related to the exploitation of aquifer systems is of particular interest in terms of risk for the possible damage to buildings and availability of water resources. We propose to realise a survey of the aquifer systems near the city of Lorca, southern Spain, using Synthetic Aperture Radar Interferometry (InSAR) with a light method necessitating a small number of interferograms rather than analysing hundreds of radar images. We computed nine interferograms with good coherence over the years 2004 and 2005. We analysed them by a two-step filtering process in order to characterise the atmospheric contribution and the ground deformation. We are then able to identify two deforming areas and quantify subsidence rates at 0.20 ± 0.02 mm/day south of Lorca and southeast to the city of Alhama de Murcia with the same efficiency as the studies using sophisticated InSAR methods. Using continuous records of water levels in boreholes, we deduced a mean storage coefficient (Sk) at 4.1 × 10− 3 which is very close to the previous published values, and coincides in this case to an inelastic deformation mode of all the system. With this value, we determine the groundwater level variations from the measurements of the ground subsidence., Depto. de Geodinámica, Estratigrafía y Paleontología, Fac. de Ciencias Geológicas, TRUE, pub

On May 11th 2011, a Mw 5.2 earthquake stroke the city of Lorca in the SE Spain. This event caused 9 fatalities, 300 injuries and serious damage on the city and the surrounding areas. The Lorca earthquake occurred in the vicinity of a region bounding two well-known segments of a large active fault, the Alhama de Murcia fault (AMF). The Lorca earthquake offers a unique opportunity to study how strain is accommodated in an intersegment region of a large strike slip fault. We map recent tectonic structures in the epicentral region and we use radar interferometry to analyze the coseismic deformation. Combining these data with seismological observations of Lorca seismic sequence we first model the source of the earthquake. Then we analyze the influence of our preferred model in the adjacent segments by Coulomb failure stress modeling. The proposed earthquake source model suggests that this event ruptured an area of ~4×3 km within the complex structure that limits the Goñar–Lorca and Lorca–Totana segments of the AMF. The induced static stress change on the adjacent segments of the fault represents a seismic cycle advance equivalent to 200 to 1000 years of tectonic loading., Depto. de Geodinámica, Estratigrafía y Paleontología, Fac. de Ciencias Geológicas, TRUE, pub

This work describes the coseismic ceiling block collapse within Benis Cave (−213 m; Murcia, SE Spain), associated with the 1999 Mula earthquake (mb=4.8, MSK VII). The collapse occurred at −156 m into the Earthquake Hall, and as a consequence one small gallery became blind. We studied the geology, topography and active tectonic structures relevant to the cave. In addition, we carried out a seismotectonic analysis of the focal mechanism solutions, and also a fault population analysis on slickensides measured in fault planes in the cave. The stress and strain regime is interpreted as being congruent with the palaeoseismic evidence, and agrees with the fault kinematics established for cave galleries developed within fault planes and growth anomalies of coral flowstone. Our analysis suggests that one active segment (NNE–SSW) determined the morphology and topography of the Benis Cave, where strong to moderate palaeoearthquakes (6≤M≤7) took place. As a consequence of this intense seismic activity a small gallery collapsed. A new palaeoseismic structure, or seismothem, has been recognized, namely the effect of palaeoearthquakes affecting the pattern of development of the spatial coral flowstone distribution located at the bottom of the cave., Ministerio de Educación y Ciencia (MEC), Depto. de Geodinámica, Estratigrafía y Paleontología, Fac. de Ciencias Geológicas, TRUE, pub

In this work we present the first conclusions obtained from the morphotectonic and seismotectonic analysis of the Benis Cave (Cieza, SE of Spain). Both analyses provide new descriptions of seismic structures formed during a known instrumental earthquake and a new type of paleoseismic feature or seismothem (a migrating coral flowstone). From the last seismothem, at least two paleoearthquakes have been identified within the cave. During the Mula earthquake (mb = 4.8, MSK VII, 1999), a massive collapse of metric blocks at -156m was reported. This direct effect caused by a low magnitude earthquake shows the high sensitivity of caves to seismic shaking in this area.