Page 317 - Caldera Volcanism Analysis, Modelling and Response

292 Valerio Acocella

Figure 3 Experiments from Marti et al.,1994. (a) Adopted apparatus; (b) section view of a col-
lapse experiment, characterised by subvertical normal faults and outward dipping reverse faults
(modi¢ed after Marti et al.,1994).

Figure 4 Experiments from Roche et al., 2000. (a) Adopted apparatus, section view; (b) sec-
tion view of three experiments characterised by di¡erent aspect ratios of the chamber roof;
(c) 3D structure of the experimental collapses with di¡erent roof aspect ratios (modi¢ed after
Roche et al., 2000).

lowering the height of the top-level of silicone in a tube connected to the main
5
reservoir (Figure 4a). The length ratio between model and nature is L B10 and
the experiments last hours to days. Several tens of experiments were performed in
2D and 3D, using a wide range of roof aspect ratios (thickness/width 0.2–4.5)
(Figure 4b). For low roof aspect ratios (r1, type A), subsidence occurs through a
broad flexure at surface and the subsequent formation of outward dipping reverse
faults (Figure 4c). When these reach a certain threshold of displacement, peripheral