COSMO-SkyMed trains its eyes on Etna
The ASI has pointed the system’s radars towards the volcano following a request from the Department of Civil Protection
10 Apr 2010
At 22.04 on 2 April 2010 the seismic monitoring network of the Italian National Institute of Geophysics and Volcanology in Catania (INGV-CT) started registering a seismic swarm in the middle of Etna’s north-eastern slope. The principal event occurred 2 km south of the Piano Pernicana tourist area at 20.04 and had a magnitude of 4.2 (at a depth of 1.1 km). From the morning of 3 April onwards the phenomenon progressively decreased in both the number of events and in their energy.
Between 17.51 and 18.27 on 8 April, the INGV-CT seismic network stations registered a dozen large low-frequency events in the area of Etna’s peak, following which there were no significant variations in the size of the volcanic tremor registered. Coinciding with this event, the crater at the eastern base of the SE Crater produced a plume of ash that rose to a height of about 1 km and dispersed in the atmosphere in a north-easterly direction, causing an ash fall in the area of Rocca Campana, between Milo and Fornazzo. This was followed by a phase of intense outgassing with no ash emission at the pit crater.
The development of these phenomena is constantly monitored by the volcanic risk group of the Department of Civil Protection (DPC), using instrument systems at its specialised centres and by processing satellite information in close collaboration with the Italian Space Agency. The ASI was alerted by the DPC and directed the COSMO-SkyMed radars towards the volcano and activated ASI’s Volcanic Risk System project (ASI-SRV) team, which uses modern satellite data analysis technology to support the volcanic risk management work of the Department of Civil Protection. Thanks to the data archive that the ASI-SRV project has been collecting on Etna for several months it was possible to respond to the request from the Department of Civil Protection in good time. In fact, by combining various radar images using a highly innovative technique developed by the IREA-CNR in Naples, it is possible to measure even very small soil deformations, in the order of centimetres, in detail.
Using these techniques, the data acquired by COSMO-SkyMed on 7 April 2010 was compared with the previously acquired data on the seismic swarm that has been occurring on Etna since the beginning of April, and in particular with data acquired on 30 March 2010. Using this comparison, the IREA-CNR, partner in the SRV project, produced the deformation map (called an interferogram) shown top left. The area affected by deformations due to seismic activity is highlighted by the white rectangle. In the image, each band of colour signifies a soil movement of about 1.5 cm moving closer or moving away from the radar position. The bands indicated by the arrows cannot be immediately attributed: the most plausible theory is that they are the effect of cloud cover over volcano that is partially disturbing the radar signal.
Finally it is important to note that the main partner in the ASI-SRV project is the National Institute of Geophysics and Volcanology (INGV), which is delegated by law to seismically monitor and survey volcanic areas as part of the Department of Civil Protection’s nationwide system. The University of Modena and Reggio Emilia, Advanced Computer Systems SpA and Galileian Plus Srl are all collaborating in the project in addition to the IREA/CNR.
