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| Titel |
Delayed earthquake-volcano interactions at Campi Flegrei Caledra, Italy |
| VerfasserIn |
Matteo Lupi, Marcel Frehner, Erik H. Saenger, Nicola Tisato, Philipp Weis, Sebastian Geiger, Giovanni Chiodini, Thomas Driesner |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250106089
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| Publikation (Nr.) |
 EGU/EGU2015-5742.pdf |
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| Zusammenfassung |
| The Campi Flegrei Caldera near Naples, Italy, is arguably one of the world’s prime examples
of volcanic hazard in a heavily populated area. Over the last centuries the ground of
the caldera went through cyclical phases of inflation and deflation. The inflation
phase consists of rapid vertical ground movements associated with the emission
of volcanic gases marked by a strong magmatic component. Such deformations
are suggested to be caused by pulses of CO2-rich fluids injected into the caldera’s
shallow hydrothermal system or by the intrusion of magmatic bodies at shallow
depths.
We show that since 1945 the uplift crises occurring at the Campi Flegrei Caldera are
caused by large regional earthquakes. Our results point out that maximum uplift rates in the
caldera take place about three years after the occurrence of large earthquakes that imposed a
log10(PGA[cm s-2]) greater than 0.18. These observations are supported by forward seismic
simulations and with a semi-quantitative statistical analysis of ground surface displacements
and Peak Ground Accelerations (PGA).
Our proposed geomechanical model integrates and simplifies previous empirical concepts
of upwelling fluids that pressurize the region beneath the Campi Flegrei causing ground
surface uplift. Numerical simulations indicate that passing seismic body waves impose
high dynamic strains at the upper boundary of the deep magma reservoir as well as
at the brittle/ductile transition at about 3 km depth. Such dynamic strains induce
short-lived brittle failure in nominally ductile regions causing the release of magmatic
fluids. The approximately 3-years time lag between the earthquake and maximum
surface uplift reflects the time during which the lithostatically pressured fluids ascend
through hot, nominally ductile lithologies without expanding. After passing the
brittle/ductile transition at ~3 km depth the H2O-CO2 mixture can expand and
phase-separate, pressurizing the subsurface. This leads to a rapid ground uplift
coupled with increasing magmatic gas concentrations in fumarole discharges. The
self-consistent mechanistic explanation of the time lag may have strong implications
in the predictive aspects of volcanic hazard assessment in the Neapolitan region
contributing to the understanding of unrest-related precursors of large dormant
calderas.
To date, clear triggering correlations could only be established for quasi-immediate
earthquake-volcano interactions (i.e., from seconds to days) with the underlying mechanisms
remaining elusive. Here we provide strong evidence for a much longer time window implying
that earthquake-volcano interactions may be much more common processes than presently
thought. |
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