THE SEISMIC MONITORING NETWORKS OF CAMPI FLEGREI (SOUTHERN ITALY) CALDERA
The Campi Flegrei caldera is one of the highest-risk volcanic areas in the world due to the large number of people living there (more than 500,000 people would be need involved in a potential evacuation phase), the vulnerability of urban buildings and the volcanic dangerousness.
The Campi Flegrei, where the last eruption occurred in 1538 AD (Monte Nuovo eruption), are characterized by bradyseisms phases showing alternative phases of subsidence and upflit in the central region of caldera. In the last decades two dramatic bradyseismic crisis occurred in the 1969-1972 and 1982-1984 with a fast ground inflation and a important increase in number and intensity of earthquakes. The total uplift measured was of about 3.5m.
Currently the Campi Flegrei are showing a new unrest started in 2005 and from 2012 the Italian Civil Defence Department declared a “yellow state” of attention. Today the total uplift from the 2005 level is about 150cm.
Since the INGV-Osservatorio Vesuviano (INGV-OV) is responsible for monitoring and studying the Campi Flegrei volcano and is the authoritative institution for the volcanic surveillance and monitoring the OV increased his effort to improve all monitoring activities and, at the same time, to strengthening its monitoring networks. The constant improvement of the monitoring networks leads to advances in the techniques and the methods to studying the monitoring data and in a mutual process these studies make it possible to improve monitoring networks in an effective and targeted manner in order to provide better quality parameters.
Due to the complexity of any volcanic systems only a multidisciplinary approach can lead to a complete understanding of its state and its possible evolution. In this context the seismology is the most useful instrument to quickly assess a volcano state change.
Here we present the INGV-OV seismic monitoring network of Campi Flegrei, the actions performed to follow the volcanic unrest and the technological evolution aimed at improving the detection capability.
Currently more than 30 stations are recording seismic data. All of them are equipped with velocimeters (SP, LP, BB and VBB sensors) and, among them, a subset is equipped with accelerometers. Moreover, by using multi channels digitizers, infrasound channels are also recorded.
To better describe the current seismic monitoring network, we will also present the performance in terms of minimum detection magnitude over time and space, and other characteristics, such as the noise power spectral density of some key seismic stations. The technological evolution aimed at improving the detection capability and at lowering the detection threshold are also discussed.