Aseismic strain episodes at Campi Flegrei Caldera, Italy

Abstract

Abstract. Since 2004 a research project has been developed to monitor subsurface deformation of Italian volcanoes using borehole strainmeters and long-baseline tiltmeters. Six Sacks-Evertson dilatometers were installed around Campi Flegrei caldera and Vesuvius during 2004–2005 (Scarpa et al., 2007), and in 2008 these instruments were supplemented by two arrays of 28–280 m long water-tube tiltmeters in underground tunnels. Relevant strainmeter and tiltmeter data have been collected and analysed from the instruments installed near Campi Flegrei caldera during the recent unrest episodes. In the period 2004–2005 strain, tilt and GPS data from Campi Flegrei indicate the onset of surface deformation that accompanied a low rate of vertical displacement that continued to 2006, corresponding to an increase of CO2 emission. This strain episode preceded caldera microseismic activity by a few months, as was observed also during a significant inflation episode in 1982. Other transient strain episodes occurred in October 2006, which were accompanied by a swarm of VT (Volcano-Tectonic) and LP (Long Period) events, in 2009, at the time of renewed gas emission activity at Solfatara, and again in March 2010, several minutes before a seismic swarm. The time scale of these transient strain events ranges from some hours to several days, putting tight constraints on the origin of ground uplifts at Campi Flegrei. Their location is compatible with a source inferred from long term deformation signals, located about 4 km beneath Pozzuoli. A proposed mechanism for these aseismic strain episodes is that they are associated with magma growth in reservoirs with occasional pressure relief associated with the leakage of gas.

Fifteen Years of Continuous High-Resolution Borehole Strainmeter Measurements in Eastern Taiwan: An Overview and Perspectives

“…Slow events are now widely observed, often accompanied by earthquake swarms or non-volcanic tremors [48,49], and together contribute to the release of the long-term earthquake strain budget in active regions [50]. Aseismic events are also observed in volcanic regions and are possibly resulting from large rainfall [51].…”

Preface to “Understanding volcanic processes through geophysical and volcanological data investigations: some case studies from Italian sites (EGU2019 GMPV5.11 session, COV10 S01.11 session)”

“…However, the described approaches and techniques are general and can be applied to any other volcanic systems. Falanga et al (2019) proposed a review on the integrated patterns of seismic and deformation observables, with the aim of recovering common relations. The study areas were two volcanic systems that behave in different ways: almost continuous open conduit activity for Stromboli (Italy), and hydrothermal activity and ground deformation for Campi Flegrei (Italy), currently interested by an unrest phase.…”

“…In the framework of the DINEV project (AMRA, Regione Campania PON, Scarpa et al, 2007) started in the Campi Flegrei -Vesuvius volcanic areas (Italy) in 2004, Di Lieto et al (2021) carried out subsurface deformation monitoring by using six Sacks-Evertson dilatometers. In 2008, they also employed two arrays of 28-280 m long water-tube tiltmeters in underground tunnels.…”