Vertical ground movements in the Colli Albani area (central Italy) from recent precise levelling

Abstract

The levelling data at Colli Albani volcanic area in the period 1950–2006, describing the main results obtained in the last 60 years are analysed. In particular, the focus is on the last two double run levellings, carried out in 2002 and 2006 respectively. Before performing these surveys, the levelling network configuration had been improvedwith the installation of new benchmarks, taking into account the ground movements inferred fromprevious studies. The data analysis shows that the strong uplift (with a maximum value of about 30 cm), occurred in the period 1950–1994 along the NW–SE levelling line bordering the SW sector of the Colli Albani caldera — Amato and Chiarabba (Geophys Res Lett 22:1985–1988, 1995); Chiarabba et al. (Bull Volcanol 59:161–170, 1997); Feuillet et al. (J Geophys Res 109:B02308, 2004); Salvi et al. (Geophys Res Lett 31:L12606, 2004); Anzidei et al. (J Volcanol Geother Res 80:55–65, 1998); Riguzzi et al. (Phys Earth Plan Inter 177:79–87, 2009) seems to have stopped after 1994. In fact, at least for the areas covered by the 1997/1999 and 2002 levelling surveys, a subsidence was highlighted in the same area previously affected by the uplift, with maximum rates similar in modulus. On the other hand, from 2002 to 2006 there is evidence of a substantial stability in the southern part of the investigated area, while in the northern area from Albano Lake to Rome, a sharp uplift (maximum value of about 3 cm) is registered.