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Land subsidence associated with overexploitation of aquifers is a hazard that commonly affects large areas worldwide. The Lorca area, located in southeast Spain, has undergone one of the highest subsidence rates in Europe as a direct consequence of long-term aquifer exploitation. Previous studies carried out on the region assumed that the ground deformation retrieved from satellite radar interferometry corresponds only to vertical displacement. Here we report, for the first time, the two- and three-dimensional displacement field over the study area using synthetic aperture radar (SAR) data from Sentinel-1A images and Global Navigation Satellite System (GNSS) observations. By modeling this displacement, we provide new insights on the spatial and temporal evolution of the subsidence processes and on the main governing mechanisms. Additionally, we also demonstrate the importance of knowing both the vertical and horizontal components of the displacement to properly characterize similar hazards. Based on these results, we propose some general guidelines for the sustainable management and monitoring of land subsidence related to anthropogenic activities, Ministerio de Economía y Competitividad (MINECO), Fac. de Ciencias Matemáticas, TRUE, pub

The natural hazards, like volcanic landslides and seismic activity, or induced by human activity (e.g. water extraction, mining,...), can have important effects in infrastructures and environment, producing great economic losses and threatening human lives. The occurrence of these phenomena are mostly related to areas that are susceptible to subsidence. Subsidence can result in permanent land loss, damage to infrastructure and buildings, and damage to the environment. Therefore, improving our understanding of the processes associated with hazards is crucial for developing systems that monitor, evaluate and predict hazards, and that aid decision makers during a crisis. Many of these hazards manifest themselves previously through deformations of the land and infrastructures. Synthetic Aperture Radar Interferometry (DInSAR) has been proved its unprecedented ability to detect millimetric displacements on the Earth surface over time scales of decades. An advanced interpretation tool Defsour, developed by the group in IGEO-CSIC, can model InSAR time series deformation data to constrain the location and geometry of the deformation sources as well as its temporal evolution. 3-D arbitrary sources for pressure and fractures/dislocations (strike-slip, dip-slip, and tensile) are adjusted. The Defsour software can automatically determine the number, nature, position, and 3D geometry of the causative source structures. In this presentation, the basic principles and case studies of the applications related to the deformation monitoring (InSAR) and deformation intepretation tool (Defsour) will be discussed and presented.

La Palma island is one of the highest potential risks in the volcanic archipelago of the Canaries and therefore it is important to carry out an in-depth study to define its state of unrest. This has been accomplished through the use of satellite radar observations and an original state-of-the-art interpretation technique. Here we show the detection of the onset of volcanic unrest on La Palma island, most likely decades before a potential eruption. We study its current evolution seeing the spatial and temporal changing nature of activity at this potentially dangerous volcano at unprecedented spatial resolutions and long time scales, providing insights into the dynamic nature of the associated volcanic hazard. The geodetic techniques employed here allow tracking of the fluid migration induced by magma injection at depth and identifying the existence of dislocation sources below Cumbre Vieja volcano which could be associated with a future flank failure. Therefore they should continue being monitored using these and other techniques. The results have implications for the monitoring of steep-sided volcanoes at oceanic islands., Ministerio de Ciencia e Innovación (MICINN), Ministerio de Economía y Competitividad (MINECO), Consejo Superior de Investigaciones Científicas (CSIC), Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

GROWTH 3.0 is a software package to determine the subsurface 3D density distribution that adjust discrete gravity anomaly values determined from gravity observations. The software uses very general assumptions and quite automatically determines the 3D density structures described by the aggregation of thousands of small rectangular prisms. A previous version of the software was published in 2011. However, methodological developments and computational technical evolution made it necessary to upgrade the software to include new advances and recent improvements in the inversion methodology (automatic determination of density contrasts, background medium with downward density increase, etc.), and a change in the computer operating system (from Windows XP, which was compatible with the 2011 version, to Windows 10 Pro for the current version). Here we describe the new upgraded version of the software package (which can be downloaded free), its use and application, using the study of El Hierro (Canary Islands) as a test case from which to obtain a 3D density model of its crustal structure. We also give a brief geological and volcanological interpretation., Ministerio de Ciencia e Innovación (MICINN), Consejo Superior de Investigaciones Científicas (CSIC), Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

La Palma island is one of the highest potential risks in the volcanic archipelago of the Canaries and therefore it is important to carry out an in-depth study to define its state of unrest. This has been accomplished through the use of satellite radar observations and an original state-of-the-art interpretation technique. Here we show the detection of the onset of volcanic unrest on La Palma island, most likely decades before a potential eruption. We study its current evolution seeing the spatial and temporal changing nature of activity at this potentially dangerous volcano at unprecedented spatial resolutions and long time scales, providing insights into the dynamic nature of the associated volcanic hazard. The geodetic techniques employed here allow tracking of the fluid migration induced by magma injection at depth and identifying the existence of dislocation sources below Cumbre Vieja volcano which could be associated with a future flank failure. Therefore they should continue being monitored using these and other techniques. The results have implications for the monitoring of steep-sided volcanoes at oceanic islands., This research was mainly funded by the Spanish Ministerio de Ciencia, Innovación y Universidades research project DEEP-MAPS, Grant Agree-ment Number RTI2018-093874-B-I00. It was also partially supported by the CSIC project 201530E019, and the project GEOSIR, Grant Agreement AYA2010-17448 from the Spanish Ministerio de Ciencia e Innovación and the MINECO research project CGL2017-86241-R. This work represents a contribution to CSIC Thematic Interdisciplinary Platform PTI TELEDETECT., Peer Reviewed, Postprint (published version)

La Palma is one of the youngest of the Canary Islands, and historically the most active. The recent activity and unrest in the archipelago, the moderate seismicity observed in 2017 and 2018 and the possibility of catastrophic landslides related to the Cumbre Vieja volcano have made it strongly advisable to ensure a realistic knowledge of the background surface deformation on the island. This will then allow any anomalous deformation related to potential volcanic unrest on the island to be detected by monitoring the surface deformation. We describe here the observation results obtained during the 2006–2010 period using geodetic techniques such as Global Navigation Satellite System (GNSS), Advanced Differential Synthetic Aperture Radar Interferometry (A-DInSAR) and microgravimetry. These results show that, although there are no significant associated variations in gravity, there is a clear surface deformation that is spatially and temporally variable. Our results are discussed from the point of view of the unrest and its implications for the definition of an operational geodetic monitoring system for the island, Ministerio de Ciencia e Innovación (MICINN), Consejo Superior de Investigaciones Científicas (CSIC), Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

The deep roots of oceanic island volcanoes are poorly known and geophysical models can help to constrain processes such as magma storage and transport before and during eruptions. Lanzarote, Canary Islands, is a volcanic island in post-erosional phase where, in the 18th century, one of the most important historical eruptions, considering duration and volume, of the Canary Islands took place in the Timanfaya area. To improve the knowledge on the structure of Lanzarote and in Timanfaya area, we carry out a gravity determination of the subsurface anomalous 3D density structure, using an improved quasi-automatic inversion methodology. The obtained model presents a 3D morphology of anomalous density bodies. We describe the improvements of the inversion methodology, the adjusted model and interpretative conclusions corresponding to the structure and the long-term cumulative magmatic plumbing system of the island. Three high-density sources are described as resulting in the inference of three main volcanic complexes: a large central complex (San Bartolomé) and two smaller complexes, one in the NE and a third smaller one located in the SW close to the Timanfaya area. The outcrops of Miocene lava flows from the center of the Island can be attributed to the top of the central intrusive model. We infer the local plumbing system for Timanfaya volcano area by means of strongly tilted successive branches of magma departing from the SW intrusive body. The structural results show no evidence of any magma chamber below Timanfaya as proposed by previous works. We also present a comparison of the gravity results and geological observations, showing different cases of correlation in the Island. They go from a good match between the gravity anomaly and the position of the central volcanic structure, to no anomaly associated to the fissural Quaternary volcanic activity., MINECO, CSIC, Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

This paper presents a thorough description of Nyamulagira’s January 2010 volcanic eruption (North Kivu, Democratic Republic of Congo), based on a combination of field observation and ground-based and space-borne data. It is the first eruption in the Virunga Volcanic Province that has been described by a combination of several modern monitoring techniques. The 2010 eruption lasted 26 days and emitted ∼45.5 × 106 m3 of lava. Field observations divided the event into four eruptive stages delimited by major changes in effusive activity. These stages are consistent with those described by Pouclet (1976) for historical eruptions of Nyamulagira. Co-eruptive signals from ground deformation, seismicity, SO2 emission and thermal flux correlate with the eruptive stages. Unambiguous pre-eruptive ground deformation was observed 3 weeks before the lava outburst, coinciding with a small but clear increase in the short period seismicity and SO2 emission. The 3 weeks of precursors contrasts with the only precursory signal previously recognized in the Virunga Volcanic Province, the short-term increase of tremor and long period seismicity, which, for example, were only detected less than 2 h prior to the 2010 eruption. The present paper is the most detailed picture of a typical flank eruption of this volcano. It provides valuable tools for re-examining former—mostly qualitative—descriptions of historical Nyamulagira eruptions that occurred during the colonial period.