← Back to Sessions

Source Mechanism and Catalog Statistics for the Last Decade of Seismicity at the Campi Flegrei Volcanic Complex, Italy.

Description: 

Over the past two years, the rate, spatial extent and magnitude of seismicity affecting the Campi Flegrei volcanic complex (Italy) have increased dramatically, accompanying ground uplift of up to 15 mm/month. Moment tensor solutions for the most significant (Md > 3) earthquakes indicate a dominance of double-couple (DC) and compensated linear vector dipole (CLVD) mechanisms. The statistical significance of these results is however questionable, and for about 80% of the cases a simple DC mechanism is sufficient to explain the data. The clustering properties of the catalog are investigated through the nearest-neighbor distances (NND) in a combined space-time-magnitude metric. The early stages of the sequence are characterized by a bimodal pattern of NNDs, associated with the background seismicity occurring at large inter-event times and distances, and clustered events separated by short temporal and spatial ranges. Such bimodal behavior is typical of environments where seismicity is purely driven by tectonic loading. Conversely, for the most recent seismicity the distribution of NNDs merges into a single-mode pattern, similar to what has been observed at Long Valley Caldera (US) and interpreted in terms of upward migration of volatile-rich volcanic fluids. The b-value of Gutenberg and Richter’s distribution does not vary significantly over time, and the same holds for Vp / Vs ratio. The thickness of the seismogenic layer exhibits significant lateral variations, with no clear correlation with the deformation pattern. All these elements suggest that seismicity is mainly driven by the combination of tensile failure in the central portion of the deforming area, and stress accumulation along pre-existing mechanical discontinuities at its border. The lack of long- and/or very-long-period seismicity, and the significance of double-couple components, indicate that either magmatic or hydrothermal fluids are not playing an active role in the seismogenic process. Nonetheless, fault weakening and/or rupture triggering by fluid pore pressure increase cannot be excluded.

Session: Multidisciplinary Approaches for Volcanic Eruption Forecasting - I

Type: Oral

Date: 5/2/2024

Presentation Time: 03:00 PM (local time)

Presenting Author: Gilberto

Student Presenter: No

Invited Presentation: 

Authors