Some Investigations on a Possible Relationship between Ground Deformation and Seismic Activity at Campi Flegrei and Ischia Volcanic Areas (Southern Italy)

Abstract

In the present paper, we analyse ground tilt and seismicity at Campi Flegrei caldera and Ischia Island, two volcanic areas located in the south of Italy. These areas have been well studied for many years from a petrological, volcanological and geophysical view point. Moreover, due to the high seismic and volcanic risk for the populations living there, they are continuously monitored by networks of geophysical and geochemical sensors. We summarize the most important results that we obtained so far, concerning the observations of relationships between seismic activity and ground tilt anomalies, focusing on the time interval 2015–2018. First, we present a detailed description of the tiltmeter and seismic networks in both the investigated areas, as well as their development and improvement over time that has enabled high quality data collection. From the joint analysis of the seismic and borehole tiltmeter signals, we often notice concurrence between tilt pattern variations and the occurrence of seismicity. Moreover, the major tilt anomalies appear to be linked with the rate and energy of volcano-tectonic earthquakes, as well as with exogenous phenomena like solid Earth tides and hydrological cycles. The analysis that we present has potential applicability to other volcanic systems. Our findings show how the joint use tilt and seismic data can contribute to better understanding of the dynamics of volcanoes.

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

“…The northern part of the resurgent block, between Casamicciola and Lacco Ameno, is marked by E-W and SW-NE faults and corresponds to the main source area of the historical seismicity (Rovida et al, 2019). In the last years, the seismic activity has been low, but on 21 August 2017 (18:57 UTC) a M d 4.0 (M w 3.9) earthquake struck the northern sector of the island, causing two fatalities and many damages in the Casamicciola area.…”

“…In the last years, the seismic activity has been low, but on 21 August 2017 (18:57 UTC) a M d 4.0 (M w 3.9) earthquake struck the northern sector of the island, causing two fatalities and many damages in the Casamicciola area. The earthquake (hereinafter referred to IE17) triggered a significant ground displacement (Devoti et al, 2018) and tilting (Ricco et al, 2019) and it was followed by a sequence of about 20 aftershocks (Nappi et al, 2018) located at shallow depths (< 2.5 km b.s.l.). The interpretation of the source process of the IE17 is still controversial: re-activation caused by tectonic stress of an E-W striking fault with south (De Novellis et al, 2018) or north (Nappi et al, 2018) dipping, or complex rupture involving a normal faulting event triggering a shallow underground collapse (Braun et al, 2018), are some of the possi-ble generation mechanisms that have been proposed.…”

Analysis and Classification of Natural and Human-Induced Ground Deformations at Regional Scale (Campania, Italy) Detected by Satellite Synthetic-Aperture Radar Interferometry Archive Datasets

“…In fact, at Campi Flegrei, after a strong uplift (about +3.30 m in Pozzuoli city center) occurred during the two 1970-1972 and 1982-1984 bradyseismic crises, a general subsidence (about −1.00 m in city center) between 1985 and 2004 has been followed by still growing uplift phases (about +0.60 m in city center). This assessment is based on levelling and GPS surveys made by INGV-Osservatorio Vesuviano [38].…”

“…Referring to the time interval of SAR acquisition (June 1992-July 2010), the Pozzuoli city center experienced a subsidence of about 30 cm from mid-1992 to late-2004 followed by an uplift of about 10 cm from early 2005 to mid-2010, causing a net subsidence of about 20 cm if referring to the whole period 1992-2010 (see benchmark 25A in [38]). This ground deformation pattern is representative of the whole caldera area, even if with lower magnitudes in peripheral sectors.…”

“…Available leveling lines and GPS data evidence subsidence at Vesuvius and Ischia [35,36] and show current southwestward velocities between 2 and 4 mm/yr at the southwestern corner of the Campanian plain [37]. At Campi Flegrei, a general subsidence between 1985 and 2007 has been interrupted by a still growing uplift phases [38].…”