Isola di Vulcano (Isole Eolie) movimenti verticali del suolo: livellazione di precisione ottobre 2003

Abstract

The levelling network installed and managed by the Osservatorio Vesuviano for monitoringvertical ground movements on Volcano island is currently made up of 100 benchmarks(bm) and extends about 24 km as a whole. The reference benchmark for calculating height variations is benchmark 1A located at Volcano Piano, which is a relatively stable area as compared with the northern part of the island. The presently operating network has been enlarged and thickened several times since June 1976, when the first levelling line was installed and surveyed. Twentyseven surveys has been conducted between June 1976 and October 2003. Actually, the configuration of the network presents a greater density of benchmarks in the center-northern sector of the island. The measurement tecnique used is precise levelling. The surveys are performed with autolevelling instruments (Wild NA2) equipped with optical micrometers and invar rods. The last levelling survey has been carried out in the first two weeks of October 2003. The comparison of September 1999 (previous levelling) with October 2003 data indicates a significant subsidence of the center-northern area of the island