Ground deformation measurements at the Soufriere Hills volcano, Montserrat:II: Rapid static GPS measurements June 1996 June 1997

We describe measurements of ground deformation around the erupting Soufriere Hills volcano made between June 1996 and June 1997 using Rapid Static GPS. The measurements define a lateral displacement field which is approximately radially symmetrical about the growing dome. No significant sustained vertical displacements have been identified. Radial displacements have generally increased steadily during this period of observation. The rate of displacement decreases from 43 cm per year at a distance of 0.6 km from the centre of the dome to about 1 cm/year at a distance of 3.8 km. Strains within one km of the dome itself are greater than 10(-3). The rate of variation of strain with distance indicates a causative centre of pressure at a depth of not greater than 750 meters below the summit of the dome

Real-time monitoring for fast deformations using GNSS low-cost receivers

Landslides are one of the major geo-hazards which have constantly affected Italy especially over the last few years. In fact 82% of the Italian territory is affected by this phenomenon which destroys the environment and often causes deaths: therefore it is necessary to monitor these effects in order to detect and prevent these risks. Nowadays, most of this type of monitoring is carried out by using traditional topographic instruments (e.g. total stations) or satellite techniques such as global navigation satellite system (GNSS) receivers. The level of accuracy obtainable with these instruments is sub-centimetrical in post-processing and centimetrical in real-time; however, the costs are very high (many thousands of euros). The rapid diffusion of GNSS networks has led to an increase of using mass-market receivers for real-time positioning. In this paper, the performances of GNSS mass-market receiver are reported with the aim of verifying if this type of sensor can be used for real-time landslide monitoring: for this purpose a special slide was used for simulating a landslide, since it enabled us to give manual displacements thanks to a micrometre screw. These experiments were also carried out by considering a specific statistical test (a modified Chow test) which enabled us to understand if there were any displacements from a statistical point of view in real time. The tests, the algorithm and results are reported in this paper