Recording the seismic tremor of the Campi Flegrei fumaroles, through seismic stations located nearby, could improve the continuous monitoring of the hydrothermal emission of the volcano. These conclusions are reached by a study by INGV, University of Palermo, Université Savoie Mont Blanc, Instituto Volcanológico de Canarias, published in Geology of the Geological Society of America
Fumaroles are known to generate a local seismic 'tremor', however the study of long-term recordings of this signal has so far received little attention. According to a study conducted by an international team of geochemists and geophysicists from the National Institute of Geophysics and Volcanology (INGV), University of Palermo, Université Savoy Mont BlancFrance, Instituto Volcanológico de Canarias, Spain. The work, entitled Fumarolic tremor and geochemical signals during a volcanic unrest, was posted on Geology of Geological Society of America
"Normally, one avoids locating permanent seismic stations near fumaroles because the 'tremor' generated by the emission of fluids makes it difficult to recognize earthquakes", explains Giovanni Chiodini, INGV research manager and first author of the publication. “Despite this, following clear increases in hydrothermal activity, in 2010 a seismometer was installed near the main fumarole of Pisciarelli, at Campi Flegrei (Fig. 1)”. The aim of the research was to have a continuous signal somehow linked to the variations in the activity of the fumarole. The data recorded by the seismic station were thus analyzed and compared with the geochemical 'signals' acquired in the same period at the Solfatara di Pozzuoli. The highly multidisciplinary approach and the first of its kind," adds Chiodini, "has highlighted how Pisciarelli's fumarolic tremor (RSAM, real-time seismic amplitude measurement) significantly increased from 2010 to 2017, correlating with the pressures and temperatures of the hydrothermal system that feeds the emission, independently estimated on the basis of the composition of the fumaroles of the Solfatara (Fig. 2)."
“The study, therefore,” concludes Chiodini, “on the one hand confirms the current period of increase in the emission of volcanic fluids at Campi Flegrei (a process already known to the scientific community), on the other it indicates how seismic stations, specifically located near fumarolic emissions, can give an important signal in real time for the purpose of monitoring hydrothermal emissions and monitoring volcanoes.
The research carried out has an essentially scientific value, with no immediate implications regarding the aspects of civil protection at the moment. Please note that since December 2012, the Civil Protection Department has raised the alert level of Campi Flegrei from green to yellow (attention).
Extended
Fumarolic tremor and geochemical signals during a volcanic unrest
- Chiodini, F. Giudicepietro, J. Vandemeulebrouck, A. Aiuppa, S. Caliro, W. De Cesare, G. Tamburello, R. Avino, M. Orazi, and L. D'Auria
Fumaroles are known to generate seismic and infrasonic tremor, but this fumarolic tremor has so far received little attention. Seismic records taken near the Pisciarelli fumarole, a vigorously degassing vent of the restless Campi Flegrei volcano in Italy, reveal a fumarole-sourced tremor whose amplitude has recently intensified. We use independent geochemical evidence to interpret this fumarolic tremor for the first time quantitatively. We find that the temporal increase in fumarolic tremor RSAM (Real-time Seismic-Amplitude Measurement) quantitatively correlates with increases in independent proxies of fumarole activity, including the CO2 concentrations in the fumarole's atmospheric plume, the fumarole composition (CO/CO2 and H2/ H2O ratios), and temperature (T) and pressure (P) conditions of the source hydrothermal system. This association between RSAM and geochemical data suggests that the current escalation in fumarolic tremor is driven by increased gas transport and venting from a hydrothermal system that evolves toward higher TP conditions. More widely, our results suggest that monitoring the tremor generated by fumaroles can pave the way to real-time tracking and interpreting the evolution of an ongoing hydrothermal-magmatic unrest, thus complementing information from periodic gas surveys. Our novel method of fumarole monitoring, based on well-established seismic techniques, is potentially suitable for capturing signals of unrest at any active volcano, including those in remote regions.
Figure 1). Location of the main fumarole of Pisciarelli and of the seismic station (CPIS) used in the work.
Figure 2) A) "Tremor" of the fumarole recorded in the period 2010-2017. The graph (reduced seismogram in the work) was obtained considering representative, of each day of acquisition, the lower value of RSAM (real-time seismic amplitude measurement) measured at night. B) The Pisciarelli seismic "tremor" (Log RSAM) is compared with the pressure and temperature estimates based on the composition of the Solfatara fumaroles.