Tidal and hydrological periodicities of seismicity reveal new risk scenarios at Campi Flegrei caldera

Abstract

The volcano-tectonic seismicity occurring at Campi Flegrei caldera during its present unrest phase, started in 2005, is distributed into time-clustered events emerging from a background composed of earthquakes with higher inter-arrival times. Here, we show that clustered seismicity is cyclically recurrent at time scales from semidiurnal to annual, matching tidal and hydrological periodicities. These results suggest that volcano-tectonic seismicity at Campi Flegrei caldera is driven by both variations in the deep magmatic feeding system and exogenous phenomena, as rainfall or global inflation/deflation cycles of the Earth’s crust, controlled by the lunisolar interaction. Consequently, the role of exogenous triggers in the evolution of the present unrest phase should be properly considered in the elaboration of volcanic risk scenarios, presently limited to the study of surface indicators of deep phenomena.

Characterization of the seismic dynamical state through joint analysis of earthquakes and seismic noise: the example of Ischia Volcanic Island (Italy)

“…The further analysis is aimed to decompose the waveforms into independent components (ICs) which represent the "basic" signals related to the source. To achieve that goal, we applied ICA (Hyvärinen et al, 2001), a technique that led to innovative results in several scientific fields (e.g., Bottiglieri et al, 2007;Palo and Cusano, 2013;De Lauro et al, 2016, 2018. It operates in time-domain and it is able to find underlying sources from multivariate statistical data on the basis of their statistical independence, evaluated by using fourthorder statistics.…”

“…In particular, the coupling between a fluid phase (e.g., magma-gas flow or hydrothermal flux) and the vibrations of the solid matrix (e.g., the volcano edifice) generates those seismic signals typically observed on volcanoes (e.g. low frequency and hybrid events, volcanic tremor; see McNutt, 2005, and references therein) and, at larger time scale, it may induce synchronization mechanisms between seismic signals and solid earth tides (De Lauro et al, 2012, 2018Falanga et al, 2019). Starting from the seminal work of Aki et al (1977) who proposed a fluid-filled crack as resonating source of the volcanic tremor observed at Kilauea, several physical models based on the fluid-rock interaction have been proposed to interpret the seismic signals in volcanic areas (see, e.g., Chouet and Matoza, 2013, and references therein).…”

“…Indeed, depending on the pressurization state, common source processes can generate different styles of activity, from continuous and sustained low-energy tremor up to higher magnitude seismic events (Chouet and Matoza, 2013;Fazio et al, 2017). This interplay between pressure-induced changes in the fluid circulations and variations of the seismic background patterns, thus represents one of the most useful observables in tracking the evolution of volcanic systems (Madonia et al, 2008;Chiodini et al, 2017;Petrosino et al, 2018Petrosino et al, , 2020. In particular, in hydrothermal environments, the fluid-rock interaction assumes a crucial role in controlling the overall dynamics.…”

A New Geospatial Model Integrating a Fuzzy Rule-Based System in a GIS Platform to Partition a Complex Urban System in Homogeneous Urban Contexts

“…The presence of volcanic hills within the municipal area has allowed for urban development, mainly below them and towards the coastal areas. A survey of the seismic activities produced by the Campi Flegrei caldera in densely inhabited areas and the consequent risk for the population was carried out in Reference [28] and recently in Reference [29]. A study of all the different cultural resources present in the Municipality of Pozzuoli performed using GIS technologies is presented in Reference [30].…”

On the link between Earth tides and volcanic degassing

“…prominently manifested in the form of the ocean tides (Ponchaut et al, 2001). 5 Evidences for tidal impacts on volcanism have been gathered by numerous empirical studies which detected a temporal proximity between tidal extrema and volcanic eruptions (Johnston and Mauk, 1972;Hamilton, 1973;Dzurisin, 1980) or seismic events Beavan, 1981, 1984;Ide et al, 2016;Petrosino et al, 2018), or found a correlation between the spring-neap tide cycle and variations in volcanic deformation (De Mendoca Dias, 1962;Berrino and Corrado, 1991) or variations in the volcanic gas emissions. 10 The tide-induced stress variations (∼ 0.1 − 10 kPa) appear to be negligibly small in comparison to tectonic stresses (∼ 1 − 100 MPa) or stresses caused by pressure and temperature gradients within a shallow magmatic system (∼ 1 MPa).…”