Geodetic Study of the 2006–2010 Ground Deformation in La Palma (Canary Islands): Observational Results

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 islan

Shallow magmatic intrusion evolution below La Palma before and during the 2021 eruption

La Palma, Canary Islands, underwent volcanic unrest which culminated in its largest historical eruption. We study this unrest along 2021 using Interferometric Synthetic Aperture Radar (InSAR) and a new improved interpretation methodology, comparing achieved results with the crustal structure. We reproduce the final phase of La Palma volcanic unrest, highligthing a shallow magma accumulation which begins about 3.5 months before the eruption in a crustal volume charactherized by low density and fractured rocks. Our modeling, together with our improved pictures of the crustal structure, allows us to explain the location and characteristics of the eruption and to detect failed eruption paths. These can be used to explain post-eruptive phenomena and hazards to the local population, such as detected gases anomalies in La Bombilla and Puerto Naos. Our results have implications for understanding volcanic activity in the Canaries and volcano monitoring elsewhere, helping to support decision-making and providing significant insights into urban and infrastructure planning in volcanic areas

Detection of volcanic unrest onset in La Palma, Canary Islands, evolution and implications

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

GNSS 3D displacement field determination in Lorca (Murcia, Spain) subsidence area

Trabajo presentado en el AGU (American Geophysical Union) Fall Meeting: Advancing Earth and Space Science, celebrado en San Francisco (Estados Unidos), del 12 al 16 de diciembre de 2016Land subsidence associated to the overexploitation of aquifers represents a common hazard impacting extensive areas worldwide. Recently, González and Fernández (20101) revealed that the Alto Guadalentín Basin, located in southern Spain, is affected by the highest subsidence rates measured in Europe (about 10 cm/yr) as a direct consequence of long-term aquifer exploitation. They used ERS and ENVISAT radar data spanning the 1992¿2007 period. They identify a delayed transient nonlinear compaction of the Alto Guadalentín aquifer due to the 1990¿1995 drought period. Bonì et al. (2015) extend the previous studies using advanced DInSAR techniques to process ALOS PALSAR (2007¿2010) and COSMO-SkyMed (2011¿2012) radar images. The combination of multi-sensor SAR images with different resolutions allows for a wider monitoring time span of 20 years (1992¿2012) over the Alto Guadalentín Basin. All regional studies of the area to date are based on satellite radar interferometry using just ascending or descending acquisitions, without any combination among them to obtain vertical and horizontal (E-W) components. It is important to obtain the 3D motion field in order to perform a correct interpretation of the observations, as well as an advanced model of the aquifer evolution, to be consider for sustainable management plans of groundwater resources and hazard assessments. With this objective, a GNSS network has been defined and two surveys have been carried out in November 2015 and July 2016. Despite the limited time interval covered by the surveys, the results allow us to obtain, for the first time, the regional 3D displacement field associated to the exploitation of the aquifer. These results, although in a preliminary form, confirm previous observations and suggest that the ad-hoc establishment of small GNSS networks represent a valuable technique for the spatio-temporal monitoring of the 3D displacement field of areas subjected to extensive groundwater extraction.Peer reviewe

Modeling the two- and three-dimensional displacement field in Lorca, Spain, subsidence and the global implications

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 activitie

Results obtained from the multiple geodetic observations at Lorca (Murcia, Spain) subsidence area

Trabajo presentado en el AGU (American Geophysical Union) Fall Meeting: Advancing Earth and Space Science, celebrado en Washington D.C. (Estados Unidos), del 10 al 14 de diciembre de 2018The Lorca region, located in the Alto Guadalentín Basin, southern Spain, shows the highest subsidence rates recorded in Europe (about 10 cm/yr). It is produced by a long-term aquifer exploitation (González and Fernández, 2011; Bonì et al., 2014). This process has been studied in various works using interferometric synthetic aperture radar (InSAR) with images acquired from different satellites (ERS and ENVISAT radar data spanning the 1992 – 2007 period; ALOS PALSAR data for the period 2007–2010; and COSMO-SkyMed data for the period 2011–2012). González et al. (2012) established a relationship between the crustal unloading produced by the groundwater overexploitation and the stress change on the regional active tectonic faults in relation with the May 2008 Lorca earthquake. Those previous studies, based on InSAR and using either ascending or descending acquisitions, assumed that the surface displacement direction is entirely vertical. However, it is important to obtain the complete 3D motion field in order to perform a correct interpretation of the observations, as well as to carry out an advanced numerical model of the aquifer evolution, to be considered for sustainable management plans of groundwater resources and hazard assessments. To achieve this goal, GNSS surveys have been carried out from 2015 to 2018, showing the regional 3D displacement field associated to the exploitation of the aquifer (Prieto et al., 2016; Fernández et al. 2017). Also, simultaneous ascending and descending InSAR observations have been used, along with structural gravimetry (Camacho et al., 2015) and microgravity to study the subsidence area in a more complete geodetic way. We present the results obtained from all those techniques, their comparison, and the interpretation results using different inversion techniques (Tiampo et al., 2011; Camacho et al., 2011, 2015; Cannavò et al., 2015).Peer reviewe

Radar Interferometry as a Monitoring Tool for an Active Mining Area Using Sentinel-1 C-Band Data, Case Study of Riotinto Mine

Soil instability is a major hazard facing the mining industry in its role of supplying the indispensable mineral resources that our societal challenges require. Aiming to demonstrate the monitoring potential of radar satellites in the mining sector, we analyze the deformation field in the Riotinto mine, Spain. We propose a new method for combining ascending and descending results into a common dataset that provides better resolution. We project the LOS measurements resulting from both geometries to a common reference system without applying any type of geometric restriction. As a projection system, we use the vertical direction in flat areas and the slope in steep topographies. We then identify and remove outliers and artifacts from the joint dataset to finally obtain a deformation map that combines the two acquisition perspectives. The results in the Atalaya pit are consistent with GNSS measurements. The movements observed in the rock dumps were unknown before this study. We demonstrate the great potential of the Sentinel-1 satellite as a complementary tool for monitoring systems in mining environments and we call for its use to be standardized to guarantee a safe and sustainable supply of mineral resources necessary for a just technological transition

Sensores remotos

Curso Observando los polos: pasado, presente y futuro, organizado por la Plataforma Temática Interdisciplinar (PTI) POLARCSIC en colaboración con la Universidad Internacional Menéndez Pelayo (UIMP) y celebrado del 4 al 8 de noviembre de 2019 en BarcelonaPeer reviewe

La investigación polar como motor de la innovación tecnológica

Curso Observando los polos: pasado, presente y futuro, organizado por la Plataforma Temática Interdisciplinar (PTI) POLARCSIC en colaboración con la Universidad Internacional Menéndez Pelayo (UIMP) y celebrado del 4 al 8 de noviembre de 2019 en Barcelona.-- Mesa redonda moderada por Jordi FelipePeer reviewe

Observando los polos: Consecuencias del cambio climático

Curso Observando los polos: pasado, presente y futuro, organizado por la Plataforma Temática Interdisciplinar (PTI) POLARCSIC en colaboración con la Universidad Internacional Menéndez Pelayo (UIMP) y celebrado del 4 al 8 de noviembre de 2019 en Barcelona.-- Mesa redonda moderada por Santiago GiraltPeer reviewe