A Methodology to Detect and Update Active Deformation Areas Based on Sentinel-1 SAR Images

This work is focused on deformation activity mapping and monitoring using Sentinel-1 (S 1) data and the DInSAR (Differential Interferometric Synthetic Aperture Radar) technique. The main goal is to present a procedure to periodically update and assess the geohazard activity (volcanic activity, landslides and ground-subsidence) of a given area by exploiting the wide area coverage and the high coherence and temporal sampling (revisit time up to six days) provided by the S-1 satellites. The main products of the procedure are two updatable maps: the deformation activity map and the active deformation areas map. These maps present two different levels of information aimed at different levels of geohazard risk management, from a very simplified level of information to the classical deformation map based on SAR interferometry. The methodology has been successfully applied to La Gomera, Tenerife and Gran Canaria Islands (Canary Island archipelago). The main obtained results are discussed.Geomatics Division, Centre Tecnològic de Telecomunicacions de Catalunya, EspañaEarth Sciences Department, University of Firenze, ItalyGeohazards InSAR laboratory and Modelling Group, Instituto Geológico y Minero de España, EspañaCentro Nacional de Información Geográfica, Instituto Geográfico Nacional, EspañaUnidad de Granada, Instituto Geológico y Minero de España, Españ

Research Group on Earth Observation, Geological Risks and Climate Change (OBTIER)

[EN] Within the framework of the IGME-CSIC Department of Geological Hazards and Climate Change, the OBTIER research group was created in July 2021 and currently has 22 members, including scientific and technical staff, as well as young people with contracts linked to competitive national and international research projects. The main objective of the group is to provide society with scientific information, methods, tools and solutions to mitigate the impact of geohazards and the effects of Climate Change. OBTIER is currently leading 6 competitive projects (4 European and 2 national), as well as several projects in agreement with other national and international administrations. It is an active member of the EuroGeoSurveys Earth Observation Expert Group and the ASGMI Geological Hazards Group. OBTIER offers society a wide range of capabilities on: earthquakes, tsunamis, landslides, land subsidence, volcanic eruptions, droughts and floods. In 2021, the group published an article in Science entitled: Mapping the global threat of land subsidence with significant media coverage around the world.Peer reviewe

Fast detection of ground motions on vulnerable elements using Sentinel-1 InSAR data

The detection of active movements that could threat the infrastructures and the population is one of the main priorities of the risk management chain. Interferometric Synthetic Aperture Radar (InSAR) techniques represent one of the most useful answers to this task; however, it is difficult to manage the huge amount of information derived from the interferometric analysis. In this work, we present a procedure for deriving impact assessment maps, over a regional test site, using as starting point Sentinel-1 SAR (Synthetic Aperture Radar) images and a catalogue of elements at risk that acts as a second input of the methodology. We applied the proposed approach, named as Vulnerable Elements Activity Maps (VEAM), to the islands of Gran Canaria, La Gomera and Tenerife (Spain), where we analysed SAR images covering the time interval November 2014–September 2016. The methodology, meant to be a powerful tool for reducing the time needed for a complete analysis of a full stack of InSAR data, is ideally suited for Civil Protection Authorities. The application of the methodology allowed to detect 108 areas affected by active deformation that are threatening one or more elements at risk in 25 municipalities of the three islands.Earth Sciences Department, University of Firenze, ItaliaGeomatics Division, Centre Tecnòlogic de Telecomunicacions de Catalunya, EspañaGeohazards InSAR laboratory and Modelling Group, Departamento de Investigación y Prospectiva Geocientífica, Instituto Geológico y Minero de España, Españ

Lichenometry of wandering blocks approaching the landslide surface velocity

20th Congress of the International Union for Quaternary Research (INQUA). Dublin, 25th and 31st July 2019, AbstractLandslides, creep slow movements and rockfalls have been widely studied from modern times by using remote sensing, which goes back up to 20 years by using GPS and INSAR and almost 100 years by using aerial photographs. The use of ancient maps and even old paintings from the 19th century allow going back up to200 years. In this work, we introduce the use of lichenometry of wandering blocks to estimate the velocity of a landslide located at El Portalet (Central Pyrenees, Spain), by using these blocks (decametric size and limestone lithology) as time and spatial markers. To do this, we have used lichenometry to estimate the age of the blocks and determinate the runout distance traveled by the blocks detached from the source area, by geomorphologic markers. We have obtained the annual growth rate (GR) of the calcicolous lichen specie Aspicilia calcarea (Hoffm.) from cemeteries, historical buildings and infrastructures for the last 300 yrs. A lineal GR value of 0.45 mm/yr has been estimated. The oldest block was dated in 600 CE ± 40 yr. and the modernone in 1750 CE ±5 yr. The analysis of aerial orthophotos and field work of the study zone reveals two N- and S-oriented chutes in which wandering blocks were located: the North path (NP) and the South path (SP). Theinventory map had been carried out taking in account the wandering blocks disseminated close to 1 km in length from the source area. The lichenometry analysis yields that the block surface velocity varies from 0.3 m/yr to =0.97 m/yr for the NP and 0.2 to 0.88 m/yr for the SP. However, the behavior of both chutes is opposite. Whereas the NP accelerates during warm climate periods and decelerates in the cold ones, on the contrary, the SP velocity decelerated during Medieval Warm Period and accelerated during the Little Ice Age (LIA). Estimations of the block wandering during the Industrial Era are approximated. INSAR and GPS velocity during the last 20 yrs. shows 0.2 m/yr. Clinometers and thermometers in boreholes indicate that during the last 20 years no permafrost was detected. Instead, the rupture plane for the landslide was estimated between 13 and 14 m depth and even 25 m depth for the SP. Differential behavior of both landslides seems to be related with the presence of water, the flux-direction and the presence of natural obstacles at the foot of the landslide.Instituto Geológico y Minero de España, Españ

Analysis of tailing dam failure based on historical documents: The case Study of "La Luciana", Spain

JTC1 Workshop. Advances in Landslide Understanding (1º. 2017. Barcelona)On 17 August 1960 the biggest disaster by death toll in Spain, related with a tailings dam failure, took place in Reocín (Santander). The tailings dam “La Luciana” failed causing the death of eighteen people, most of them children. The mining company carried out several geotechnical tests in the remaining materials of the tailings dam to understand the failure. In addition, thematic cartography related to the break was elaborated. The results are available to be consulted in the Reocín Mines Documentary Collection, from which we have obtained mechani cal Cone Penetration Test (CPT) data near the fault area as well as diverse maps of the dam pre-failure and post-failure. The processing of such data through current analysis techniques has revealed the relationship between the fault of the tailings dam and static liquefaction phenomena.Departamento de Investigación en Recursos Geológicos, Instituto Geológico y Minero de España, EspañaGeohazard InSAR Laboratory and Modelling Group, Instituto Geológico y Minero de España, EspañaPeer reviewe

Coastal lateral spreading in the world heritage site of the Tramuntana Range (Majorca, Spain): the use of PSInSAR monitoring to identify vulnerability

The Bàlitx area is located on the steep coastal side of the Tramuntana Range (Majorca), a mountainous region which was declared a World Heritage Site by UNESCO in 2011 in the cultural landscape category. The Bàlitx site was occupied by farming areas with dry stone constructions and water storing systems of both Roman and Islamic origin. The coastal landscape is characterised by a large fault escarpment of up to 260 m in height. Lateral spreading processes are favoured by local stratigraphy and tectonics in an energetic coastal dynamics scenario. Block spreading morphologies are identified along the escarpment, with large, rocky blocks of volumes up to 60 × 103 m3 moving very slowly until their collapse. Consequently, a thick and highly karstified breccia deposit is accumulated at the base of the scarp. The lowest, oldest breccia outcrop has been dated (Th/U), and an age of 82.5 ± 5.6 kyr was obtained, reflecting the time span this process has been active. Additionally, numerous geomorphological slope features are identified in the area: landslides, rockfalls, and, more specifically, long and deep cracks in the hanging wall block of the fault, which also reveal active lateral spreading processes. Coastal dynamics have been investigated by interpreting offshore geophysical studies, bathymetry data and borehole information to determine the role of wave energy in the stability of the slope. Additionally, 14 SAR images from the ALOS PALSAR satellite have been exploited for the present work, covering a period spanning from 2007 to 2010, an anomalous rainy period in the region. Images were processed using the Persistent Scattered Interferometry (PSI) technique. PSInSAR results reveal that the rate of movement for the Bàlitx lateral spreading is extremely low (− 5.2 mm/year on average), but major activity has been detected in the NE sector, where velocity rates can reach values of up to − 16 mm/year Coastal dynamics in the area can explain this, as a small island generates wave refraction and reflection determining more intense erosive processes in the NE part, which lead to a greater destabilising effect on the slopes. A simple vulnerability approach has been developed to take the elements of cultural heritage into account. Vulnerability increases from SW to NE, in accordance with landslide activity. The Bàlitx case study could provide a testimony to the effects of mass movements and coastal dynamics in an exceptional example of Mediterranean agricultural landscape.Área de Riesgos Naturales, Instituto Geológico y Minero de España, EspañaGeohazards InSAR Laboratory and Modeling Group, Instituto Geológico y Minero de España, EspañaInstituto Andaluz de Ciencias de la Tierra, Universidad de Granada, EspañaDepartamento de Geodinámica, Universidad de Granada, EspañaUniversitat de les Illes Balears, EspañaDipartmento per il Servizio Geologica d’Italia, Istituto Superiore per la protezione e la Ricerca Ambientale, Itali

Identification and Management of Indirect Volcanic Risks: Citizens’ Rockfall Observatory on the Island of El Hierro

[EN] Secondary volcanic hazards (SVH) are not usually considered in volcanic hazard analysis, nor are they specifically included in volcanic risk management plans. However, SVH may cause more damage than primary volcanic hazards (PVH). The magmatic unrest on El Hierro Island in 2011–2012 is a perfect example of how SVH can be one of the leading causes of damage during magmatic unrest. Rockfalls are common on the island of El Hierro, mainly controlled by the heterogeneous lithology and the steep topography. Heavy rainfall and strong wind are usually the main triggering factors. However, during the 2011–2012 El Hierro Island magmatic unrest most of them were triggered due to earthquakes. Rock falls caused roadblocks and damage to road infrastructure. Two reports analysing rockfall hazards and associated risks during the emergency were based on expert knowledge and highlighted the need for, a comprehensive inventory of rockfalls, their processes characterisation, recurring event timing estimations and an analysis of their triggering factors. The need for better rockfall understanding on El Hierro island and the extensive experience of the local Civil Protection agents that were already working with citizens during the volcanic emergency, led to the development of a Rockfall Citizen’s Observatory. The observatory aims to engage citizens in the study of this geological hazard, hence providing a substantial increase in the amount of high quality data for rockfall risk analysis.Peer reviewe