With the measurement of the seismic tremor generated by the Pisciarelli fumaroles it is possible to monitor the variations in the Campi Flegrei caldera. It is the result of a new study by INGV, conducted in collaboration with the Université Savoie Mont Blanc
The Pisciarelli hydrothermal area is a key site for monitoring the Campi Flegrei, and analysis of seismic tremors from the fumaroles can provide information on the caldera's activity. This is the result of the research "Insight into Campi Flegrei caldera unrest through seismic tremor measurements at the Pisciarelli fumarolic field," conducted by a team of geophysicists and geochemists from theIstituto Nazionale di Geofisica e Vulcanologia (INGV), just published in the journal “Geochemistry, Geophysics, Geosystems” of the American Geophysical Union.
“The Campi Flegrei”, explains Flora Giudicepietro, researcher at the Vesuvius Observatory of the INGV (OV-INGV), “are a volcanic caldera, formed following the emptying of a superficial magma chamber, due to the great eruption of the Campania Ignimbrite of about 40.000 years ago. This area, rich in history, is characterized, like many calderas in the world, by deformations, seismicity and the presence of a vast hydrothermal system”.
Since the XNUMXs in this area there have been episodes of intensification of volcanic phenomena characterized by earthquakes and ground uplift, known as bradyseism.
“In the past”, continues the researcher, “on various occasions we have witnessed an intensification of bradyseism: in particular around 1950, in the period 1968-72 and in the period 1982-85. From 2004 to today, Campi Flegrei has witnessed a moderate but progressive variation of volcanic manifestations such as uplift, seismicity represented by low-energy earthquakes and the activity of the hydrothermal system which has become more intense”.
The variation of these processes between the end of 2012 and the beginning of 2013 led the Department of National Civil Protection (DPC) to raise the alert level from green (basic) to yellow (attention).
“The long-term analysis of the seismic tremor generated by the fumarole in question indicates an increase in the amplitude of the fumarolic tremor between May 2017 and the end of April 2019, an increase which is reflected in the trends of the geochemical parameters recorded in the Campi Flegrei. Seismicity after 2000 provides a clear picture of this process: earthquake locations and hypocentral density delineate the paths of fluids moving from a large area within the hydrothermal system, at a depth of 1-2 km, towards the hydrothermal sites of Pisciarelli-Solfatara, where the events are concentrated at very low depths (<1 km). Analyzing the amplitude of the fumarolic tremor”, concludes the expert, “it was also possible to identify an episode of enlargement of the emission area near the main Pisciarelli fumarole”.
The published research has an essentially scientific value, without immediate implications regarding the aspects of civil protection at the moment.
Figure 1 - Map of the Campi Flegrei caldera (left) and of the Pisciarelli hydrothermal area (right). In the left panel, the red line indicates the rim of the caldera and the orange circle highlights the Solfatara-Pisciarelli hydrothermal area. The right panel shows Pisciarelli's fumarolic field. The blue circles indicate the locations of the seismic stations and the green circle indicates the location of the main fumarole
Figure 2 - Amplitude of the seismic signal of the vertical component of the CPIS station. The blue dots represent the time series published in Chiodini et al. [2017]. The red dots indicate the time series from 1 May 2017 to 23 April 2019. The maximum, in the period studied, is 29 November 2018
Figure 3 - Seismicity in Campi Flegrei since 2000. Left, locations of earthquakes recorded in Campi Flegrei since 2000. Right, hypocentral density. The minimum value (light yellow) is two earthquakes per cell; the maximum (red) is 10 earthquakes per cell. The red arrow indicates the position of the Pisciarelli hydrothermal area. Plots have a vertical exaggeration of 2