Signature of magmatic processes in strainmeter records at Campi Flegrei (Italy)

Abstract

Volcanic unrest at Campi Flegrei caldera, Southern Italy, is characterized by episodes of ground deformation, seismicity, and enhanced fumarolic activity; whether its origin is purely hydrothermal or magmatic is highly debated. We have identified ground deformation patterns in strainmeter records from a heightened unrest period in late 2006, closely resembling synthetic signals from numerical simulations of shallow magma chamber replenishment and mixing. Together with other recent findings, our results depict a situation whereby periodic arrivals of deep magma feed a shallow intrusion at 3–4 km depth. These results suggest that the analysis of strainmeter records, coupled with advanced numerical simulations of magma dynamics, could lead to new approaches in imaging subsurface dynamic processes in volcanic areas.

Increasing CO<sub>2</sub> flux at Pisciarelli, Campi Flegrei, Italy

“…Our results related to the CO 2 degassing are compatible with findings which state that the elastic rock matrix of CF is transitioning to inelastic behavior under long-term stress accumulation, accompanied by a permeability increase in the shallow crust, disguising any direct indicator of unrest, such as rapid ground uplift or enhanced seismicity (Bodnar et al, 2007;Di Luccio et al, 2015;Kilburn et al, 2017). In line with this prospect is a clear seismic velocity decrease since 2012 (Zaccarelli and Bianco, 2017), which could be due to, for instance, a softening bulk or increase in CO 2 saturation in the CF aquifer (Queißer and Singh, 2012) that may also explain the strong seismic attenuation observed (De Siena et al, 2017b).…”

“…As all calderas, CF represents a complicated makeup that includes a magmatic plumbing system with a depth of up to ∼ 8 km (Bodnar et al, 2007;Zollo et al, 2008;Vitale et al 2014;Moretti et al, 2017), feeding the overlying hydrothermal system (Chiodini et al, 2010;Troiano et al, 2011;De Siena et al, 2017a) through an intricate network of fractures (Zollo et al, 2008;De Siena et al, 2010;Byrdina et al, 2014). A clear picture of the feeding mechanisms and its dynamics is one of the central open questions regarding CF and is subject to ongoing debate.…”

“…An increase in the supply of fluids and associated thermal energy into the hydrothermal system for depressurization of the magmatic source (Allard et al, 1991;Chiodini et al, 2016). This increased supply is thought to stem from either the ∼ 8 km deep main magma reservoir (Bodnar et al, 2007;Zollo et al, 2008;Moretti et al, 2017) or from a contribution of a magma batch that intruded into the shallow subsurface (∼ 3-4 km depth) concomitantly with the 1982-1984 unrest episode (Chiodini et al, 2010;Caliro et al, 2014) and is periodically rejuvenated by arrivals of deep, more primitive magma (Bagagli et al, 2017).…”

Aseismic strain episodes at Campi Flegrei Caldera, Italy

“…Approximately 74 cm of uplift occurred between 1950and 1952(Del Gaudio et al, 2010, but without any report or record of associated seismic activity. Slow subsidence followed this period of uplift interrupted in 1970-1972 and in 1982-1984 by rapid (≈ 1.5 m) inflation episodes, the first accompanied by moderate low seismicity (Corrado et al, 1977) with only few events felt by residents, whereas the second was accompanied by relatively intense swarms of volcano tectonic (VT) earthquakes (Barberi et al, 1986). This seismic activity caused alarm in the population and a spontaneous partial evacuation of the city of Pozzuoli (44 000 residents).…”

Magma Mixing: History and Dynamics of an Eruption Trigger

“…Vesiculation induced by convection increases magma pressure and may fracture the volcanic edifice triggering an explosive eruption. The injection and mixing process is accompanied by geophysical signals, such as earthquakes, gravity changes and ultralong-period ground oscillations, that can now be accurately detected (Williams and Rymer 2002;Longo et al 2012;Bagagli et al 2017). The knowledge of the time elapsing between the beginning of mixing (and associated geophysical signals) and eruption is thus of greatest importance in forecasting the onset of a volcanic eruption.…”