Figure 6

Event tree of the different volcano deformation patterns produce by the intrusion of a viscous magma body and the possible catastrophic eruptive scenarios in case of edifice lateral collapse. Map views show the deformation features (lines: faults; dark grey areas: subsidence; light grey areas: uplift) produced with each deformation pattern, together with the qualitative temporal behaviour of two hypothetical GPS stations located at the summit (S) and the flank (F) of the volcano continuously recording vertical (z) and horizontal (x) displacements. Sketched cross-sections show the development of deformation patterns 1 and 2 that do not produce deformation structures which induce the volcano instability, whereas deformation 3 produces a clear unstable situation. If deformation pattern 3 is detected, then two different eruptive scenarios can evolve in relation to the time of the volcano collapse. The “lateral collapse – plinian eruption” scenario is produced when the intrusive body is still located below the slip surface and therefore is not involved in the collapse (Early Collapse). “Bezymianny-type” (lateral collapse - lateral blast - plinian eruption) scenario is produced when part of the magmatic body has intruded inside the sliding block (Late Collapse). In late collapse there is dilation, then exposure of the magma body, producing a magmatic lateral directed blast.