Modelling of the rising phase of the fluid mass from about 9 to 2.5 km depth and following diffusion of the fluids within the carbonate aquifer. (a) Map showing the gravity stations (red squares) and the trace of the profile (red line; see the plot b). The various black circles report the distance reached by the diffusion front of our synthetic models. Coordinate system of map is UTM 33 N. (b) Topographic section of the Vesuvius cone with simplified geological scheme (dots: volcanic units; bricks: carbonate units; dashed area: hydrothermal system and white area: conduit). Red and orange circles locate the position of the fluids during the phases of ascension. Orange is relative to the final depth reached at the end of the rising phase (2.3 km), while red is relative to a possible location of the fluids in 2009–2010 (see the text for further details). The blue dashed arrows illustrate the diffusion process occurring after 2012. (c) Simulation of the increase in gravity due to an ascending sphere with fluids (density 1000 kg m−3) and volume of 9.5 × 107 m3 that is rising from 9 to 2.3 km depth (black lines with different line styles; corresponding depth is reported on the left of each line). The coloured lines report the gravity differences with respect to 2007 November at successive years. (d) Simulation of the gravity reduction due to the diffusion process (continuous lines); the colour code is relative to different phases of the diffusion shown in (a).
