Lipari-Vulcano discrete geodetic networks
Lipari-Vulcano discrete geodetic network (reference: Alessandro Bonforte)
Since the late 1970s, a systematic collection of ground deformation data at Vulcano Island has been carried out by the Istituto Nazionale di Geofisica e Vulcanologia (formerly Istituto Internazionale di Vulcanologia – Consiglio Nazionale delle Ricerche).
A first EDM network was installed in 1975 and covers the entire island of Vulcano and the southern part of Lipari island. All benchmark of this network consist in concrete pillars. There are 6 pillars on Lipari and 8 on Vulcano.
GPS technique replaced the EDM one and currently, at least one GPS survey per year is carried out on this network.
Vulcano-Nord network
Successively, in 1987, a new EDM network upgraded the former in the area of the “La Fossa” cone. This new and denser network consisted of four profiles of three benchmarks along the northern, western and southern slopes of the cone. Each benchmark on the cone was measured from two of the stations around the caldera, belonging to the wider network connecting Lipari and Vulcano islands.
From 1987, the EDM network covering the active volcanic structure of “La Fossa” cone was periodically reoccupied at four-monthly intervals until 1997. Now, GPS measurements are carried out on this network, at least yearly. Usually, two fast-static sessions (20-30 mins) are carried out on each benchmark of the Vulcano-Nord network, while static sessions are being carried out on the Lipari-Vulcano stations.
La Forgia network
With the aim of improving the detail of the investigation, in May 1990 a denser array composed of 12 benchmarks was installed in the northern sector of the crater terrace of “La Fossa” and measured by EDM techniques from the northern promontory of the island (Vulcanello). Six benchmarks of the network V3 (already existing), F4, F5, F6, F7, F8 (V3/F4-F8) were positioned above the “La Forgia” depression, characterised by intense fumarolic activity and slope instability. The other benchmarks F1,F2, F3 (F1-F3) and F10, F11, F12 (F10-F12) were installed in relatively more stable bordering areas along the rim in order to control the extension of the deforming area and verify any bias affecting the measurements.
