Publication Date:
2021-03-10
Description:
This article presents findings from two episodes of seismicity and gas emission that
occurred on 7 October 2015 and 6 December 2019 in Campi Flegrei caldera. This caldera
has been affected by long-term unrest since 2004. The 6 December 2019 episode, consisting
of a swarm of 38 earthquakes (maximum duration magnitude 3.1, the largest
between 1984 and March 2020), occurred at the end of a one month period characterized
by an increase in the ground uplift rate from 0:19 0:01 to 0:72 0:05 mm= day. A
sudden increase in the fumarolic tremor amplitude, which is a proxy of gas emissionrelated
parameters recorded at Solfatara–Pisciarelli hydrothermal area (e.g., CO2 air
concentration), was observed during the seismicity episode. The uplift rate decreased
immediately after the swarm (0:10 0:01 mm= day), whereas the fumarolic tremor
amplitude remained higher than that observed prior to the swarm. Through analyzing
the time series of uplift recorded in Pozzuoli (central area of the caldera) from differential
measurements on tide gauges, we were able to identify the 2015 episode. This
episode was characterized by increasing uplift rates that culminated in a seismic swarm
of 33 earthquakes on 7 October, which was followed by decreasing uplift rates. We
computed double-difference locations of earthquakes from the two swarms and found
that they located along a conduit-like path, coinciding with a high-resistivity contrast
zone, previously identified by audiomagnetotelluric measurements. The focal mechanisms
of the major earthquakes of both swarms indicate fault planes radial with respect
to the maximum uplift area. These phenomena can be interpreted as episodes of the
volcanic and (or) hydrothermal system pressurization that culminate in an injection of
fluids along the conduit-like path, which behaves as a valve that allows fluid discharge
and the temporary depressurization of the source region.
Description:
Published
Description:
965–975
Description:
4V. Processi pre-eruttivi
Description:
JCR Journal
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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