Instituto Geográfico Nacional (IGN) is the institution responsible of volcanic monitoring and alert in Spain. The IGN monitoring system has been designed to be able to detect changes in evolution of the data recorded by the surveillance networks (seismic, geodetic, geochemical, geophysical, and thermal networks) and to interpret them in terms of possible changes in the eruptive process, establishing prognosis of future evolution including scenarios of different hazards. IGN has to communicate this information to the volcanic risk managers (Civil Protections), as scientific alerts, reports, and personal communication. This scientific alert triggers the activation of the Civil Protection Emergency Plans.
Deformation is one of the parameters that can reflect a change in the volcanic system, which can potentially lead to an eruption. Products generated by the Volcanic Early Warning System (VEW), described in the following sections, have an important effect on improving the monitoring system of IGN as they provide an excellent spatial coverage of deformation with an updating frequency of six days. VEW aims to generate products of deformation which integrates results coming from different geodetic techniques (InSAR, GPS mainly). These results, together with other geophysical information coming from the monitoring networks, can act as input parameters of volcanic assessment software to hold volcanic hazard and risk management.
The starting point of VEW are the deformation maps generated by InSAR techniques using Sentinel-1 data. The methodology to generate these products is the first part of this WP. In a second stage, those maps are integrated with deformation data coming from IGN monitoring networks. The methodology to generate IGN products and the way they are integrated in the VEW constitute the second and third parts of this WP.
Find here de related deliverbles: WP3 Deliverables
Sentinel-1 processing: Deformation Activity Map & Active Deformation Areas map
The three measured islands, La Palma, Hierro and Tenerife, are covered by a single Sentinel-1 frame. The dataset consisted of 83 Sentinel-1 Wide Swath, covering one year and 8-month period, starting in January 2017 and ending in August 2018.
The S-1 data processing has been done by using and tuning the software tools developed by CTTC in the framework of the European Project Safety ( http://safety.cttc.cat/).
The procedure used in this test site, is based in the direct integration of consecutive interferograms (see Barra et al. 2016). The main goal is to fully exploit the high coherent phase of the 6-day interferograms with two purposes: (i) to obtain a good coverage at regional scale and (ii) to be able to detect relatively fast displacements. With this aims, a new approach has been tuned, based on the split of the interferograms in two components. The phase splitting consists in the application of a space filtering to each interfeogram to discriminate those signals that have a smooth phase changes in space (mainly atmospheric contribution) from those with higher space gradients (ground displacements or topographic errors).
In the image below, are represented the key steps to derive the maps. The input of the procedure is a set of N images, the corresponding N-1 complex-interferograms formed by consecutive image pairs, and a Digital Elevation model.
The main outputs of the procedure are on one hand the deformation time series and the estimated velocities over the selected points (Displacement Activity Map - DAM), on the other hand the low-frequency-component of each interferogram. We refer to the related documents (listed below) for more details about the processing steps and the results.
Based on the DAM, the main Active Deformation Areas have been extracted to generate the ADA map, using the ADAFinder software, developed in the framework of the Safety (http://safety.cttc.cat/) and Mommit (https://www.momit-project.eu/) EU projects (Barra et al. 2017; Navarro et al. 2018).
Integration of U-Geohaz products in the volcano monitoring activities
The main objective is to integrate deformation monitoring from different techniques to have a broader vision of the deformation field in the Volcano Monitoring System and risk management. In this project we have integrate de U-Geohaz products (DIM, DAM and ADA) derived from satellite Differential Interferometry (DInSAR) with GPS data coming from the daily processing of the GPS network that IGN has in Canary Islands. For this integration it is necessary to project GPS date to LOS, in order to be able to compare with InSAR data.
With this aim guidelines, addressed to Civil Protection prevention departments, have been developped for a proper integration, use and interpretation of the products obtained in WP3, as a support to early warning system for volcanic hazards.