Figure - Ischia's multi-parameter monitoring networks
Figure tiltmetric data - Cosismic, permanent tiltmetric deformations observed at the ISC (red arrow) and FOR (green arrow) stations. The star in blue indicates the epicenter of the earthquake of 21 August (image and elaboration by Ciro Ricco, Vincenzo Augusti, Giovanni Scarpato and Ida Aquino, INGV-Osservatorio Vesuviano).
SEISMIC MONITORING
Seismic monitoring of Ischia is carried out through the joint use of a Permanent Seismic Network and a Mobile Seismic Network, managed by the INGV section of Naples Vesuvius Observatory (Fig. 1). These networks make it possible to identify and classify seismic signals linked to earthquakes or other natural and artificial phenomena. The seismic events detected and localized are then archived in specific catalogues, which can also be consulted online (databases link).
Permanent Seismic Network
The Permanent Seismic Monitoring Network of Ischia has 8 permanent installation sites on the island plus one site on the island of Procida. Different types of stations and sensors can be set up at each site. Overall, the network is made up of 3 analog stations with short-term sensors and 8 broadband digital stations. The digital seismic stations are based on the GILDA data logger, designed and produced at the Vesuvius Observatory, and on Guralp DM24 data loggers. An infrasonic Infracyrus microphone and a Chaparral broadband microphone are added to the sensors of the seismic network. All the signals detected by the indicated sensors are transmitted in real time to the Monitoring Room of the INGV Vesuviano Observatory in Naples, where they are analyzed and processed.
Mobile Seismic Network
On the island of Ischia there are 6 mobile seismic stations, equipped with broadband seismic sensors. Three stations transmit the signals in the Monitoring Room of the Vesuvius Observatory, while the rest of the instruments work in local acquisition mode.
GEODETIC MONITORING
The monitoring of soil deformations on the island of Ischia is based on an integrated approach of continuous measurements and periodic campaigns, carried out with instrumental networks relating to various parameters managed by the Naples Vesuvius Observatory section. The measurement and observation techniques used are GPS, tiltmetry and precision geometric levelling. A fixed GPS network, an altimetric network, a tiltmetric network and a gravimetric network are installed (Fig. 1). Periodically, the staff of the Vesuvius Observatory carries out precision leveling campaigns on an altimetric network made up of about 250 strongholds, and gravimetric measurement campaigns on a network made up of 25 strongholds. The analysis of the acquired data is carried out separately for the signals of the various networks and subsequently integrated into a single database.
GPS network
There are 6 permanent and operating GPS stations on the island of Ischia; a GPS station is also present on the island of Procida. Latest generation Leica GR10 or GRX1200PRO series receivers are used for all sites. The collected data is transmitted to the operational headquarters of the INGV Osservatorio Vesuviano with various technologies, according to the logistics of the site. The transmission systems currently in use use Wi-Fi connections, ADSL, UMTS/4G and GSM lines. Most of these stations are mains powered. Only two sites are powered by solar panels. The management and data transmission system is based on specific software.
Mareometric network
The Mareographic Network of Ischia consists of one station. The tide level is monitored by means of a float sensor (in still-pipe) connected to a digital encoder. The signals, sampled every minute, are acquired and transmitted via GSM modem. The power supply is of the solar type with photovoltaic panels. The station is installed in a metal cabin and fiberglass container. The location in a marine environment considerably affects the accommodation facilities, therefore frequent maintenance is essential.
Tiltmetric network
The Tiltmetric Network of Ischia consists of 3 stations, equipped with digital well sensors model Lily (Jewell Instruments). The stations transmit the recorded data files daily to the Monitoring Room of the Vesuvius Observatory (Fig. 2).
GEOCHEMICAL MONITORING
Geochemical monitoring activities in Ischia consist of the collection and chemical and isotopic analysis of gas and thermal water samples during periodic measurement campaigns. These activities are carried out by the INGV section of Palermo in collaboration with the Vesuvian Observatory. The chemical-physical characteristics of the samples taken allow us to obtain information on the state of the island's geothermal system.
Geochemical networks
There are no networks of continuous stations for the measurement of geochemical parameters. 16 sampling points have been identified for thermal waters (in wells and springs) and 3 points for gaseous emissions. In addition to the sites that are part of the Surveillance Network, the gases emitted by 6 submarine fumaroles are sampled.
VOLCANOLOGICAL MONITORING
The volcanological monitoring activities on the island of Ischia are carried out by the Naples Vesuvius Observatory Section through measurement campaigns carried out with a Mobile Thermal Camera and Thermocouple. Monitoring with thermal cameras has as its main objective the identification of variations in time and space of the temperature values measured on the ground in significant points of the crater area.
Discreet Monitoring with Mobile Thermal Cameras (TTM) and Thermocouple
Thermal surveys are carried out on 9 sites on a monthly basis, at night and in any case in conditions of no solar radiation, using a high resolution and sensitivity FLIR SC640 portable thermal imaging camera. The thermocouple used is type K. The measurements obtained with the thermocamera are compared, when possible, with those performed with a rigid thermocouple.