Since 2004 a research project has been developed to monitor subsurface deformation of Italian volcanoes us- ing 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 un- derground tunnels. Relevant strainmeter and tiltmeter data have been collected and analysed from the instruments installed near Campi Fle- grei caldera during the recent unrest episodes. In the period 2004–2005 strain, tilt and GPS data from Campi Flegrei indi- cate the onset of surface deformation that accompanied a low rate of vertical displacement that continued to 2006, corre- sponding 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 com- patible with a source inferred from long term deformation signals, located about 4km 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.

Aseismic strain episodes at Campi Flegrei Caldera, Italy

Roberto Scarpa
2021-01-01

Abstract

Since 2004 a research project has been developed to monitor subsurface deformation of Italian volcanoes us- ing 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 un- derground tunnels. Relevant strainmeter and tiltmeter data have been collected and analysed from the instruments installed near Campi Fle- grei caldera during the recent unrest episodes. In the period 2004–2005 strain, tilt and GPS data from Campi Flegrei indi- cate the onset of surface deformation that accompanied a low rate of vertical displacement that continued to 2006, corre- sponding 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 com- patible with a source inferred from long term deformation signals, located about 4km 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.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11386/4760241
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