Page 415 - Caldera Volcanism Analysis, Modelling and Response

390 Claudia Troise et al.

anyway related to arrival of the new magma in the chamber (as also the CO 2
increase suggests), then each overpressure pulse adds up to increase the magma
chamber total pressure bringing the system progressively closer to the critical point
for rock failure and eruption (see De Natale et al., 2006).
The present results suggest that continuous monitoring of horizontal to vertical
displacement ratios with CGPS should be considered one of the best methods to
detect intrusive phenomena at volcanoes. At Campi Flegrei caldera, we have shown
that this method is easily applicable with relatively few continuous monitoring
points, due to the remarkable stability of the source axis as revealed by the constancy
of the vertical ground deformation pattern. However, in general, CGPS sampling
should be dense enough to detect all possible changes in source location.
Furthermore, the new frontier of volcanic surveillance and forecast should be
continuous monitoring of different strain components with directional strain meters
in deep wells, where noise is drastically lower and measurements are generally
sensitive enough to allow detection of the smallest signals of volcanic unrest and
magma migration.

ACKNOWLEDGMENTS

We thank the reviewers A. Gudmundsson and A. Newman for their helpful suggestions and Janine
Kavanagh for her correction of English grammar. This work has been partially supported by MIUR-
PON Petit-Osa, and SIMONA funds and MIUR-FIRB RBAU01M72W_001.

REFERENCES

Barberi, F., Hill, D.P., Innocenti, F., Luongo, G., Treuil, M., 1984. The 1982–1984 bradyseismic crisis
at Phlegrean Fields (Italy). Bull. Volcanol., 47, 173–411.
Battaglia, M., Troise, C., Obrizzo, F., Pingue, F., De Natale, G., 2006. Evidence for fluid
migration as the source of deformation at Campi Flegrei caldera (Italy). Geophys. Res. Lett.,
33(L01307-10), doi:10.1029/2005GL024904.
Beauducel, F., De Natale, G., Obrizzo, F., Pingue, F., 2004. 3-D modelling of Campi Flegrei ground
deformations: role of caldera boundary discontinuities. Pageoph, 161, L01307, doi:10.1007/
S00024-004-2507-4.
Bellucci, F., Woo, J., Kilburn, C.R.J., Rolandi, G., 2006. Ground deformation at Campi Flegrei,
Italy: implications for hazard assessment. In: Troise, C., De Natale, G.Kilburn, C.R.J. (Eds),
Mechanisms of Activity and Unrest at Large Calderas. Geological Society, London Special
Publication, Vol. 269, pp. 141–157.
Beutler, G., Bock, H., Brockmann, E., Dach, R., Fridez, P., Gurtner, W., Hugentobler, U., Ineichen,
D., Johnson, J., Meindl, M., Mervart, L., Rotacher, M., Schaer, S., Springer, T., Weber, R.,
2001. Bernese GPS Software Version 4.2, AIUB, University of Berne.
Capuano, P., Achauer, U., 2003. Gravity field modelling in the Vesuvius and Campanian area. In:
Zollo, A., Bobbio, A., Gasparini, P., Casale, R.Yeroyanni, M. (Eds), TomoVes Seismic Project:
Looking Inside Mt. Vesuvius. Cuen, Napoli, under sponsorship of European Commission,
project ENV4-980698, e-book.
Chiodini, G., Todesco, M., Caliro, S., Del Gaudio, C., Macedonio, G., Russo, M., 2003. Magma
degassing as a trigger of bradyseismic events: the case of Phlegrean Fields (Italy). Geophys. Res.
Lett., 30(8), 1434, doi:10.1029/2002GL016790.