MEDUSA: a real-time multi-parameter marine monitoring research infrastructure

Abstract

MEDUSA stands for Multiparametric Elastic-beacon Devices and Underwater Sensors Acquisition system. It is a marine monitoring research infrastructure based on instrumented geodetic-buoys with cabled seafloor multi-parametric modules operating in the Gulf of Pozzuoli (Naples, Italy) within the Campi Flegrei caldera. It mainly monitors the local seismicity and the seafloor movements (bradyseisms). MEDUSA consists of four buoys and as many submarine cabled modules, at water depth ranging from 38 to 96 meters, equipped with geophysical and oceanographic sensors. The infrastructure has been present since 2016 and allows the acquisition and transmission of all data in real time at the INGV (Istituto Nazionale di Geofisica e Vulcanologia, Italy) monitoring center in Naples, where they are integrated with those acquired by the on land networks. This new and augmented implementation is based on the previous experience gained during the realization of CUMAS (Cabled Underwater Multidisciplinary Acquisition System), the first prototype of instrumented buoy operating in the Gulf of Pozzuoli since 2008. CUMAS has allowed the acquisition of new skill in the design and management of fixed marine monitoring systems in shallow waters, making possible to reach precious reference points in the field of geophysical monitoring technologies. Each of buoys is equipped with a standard geodetic GNSS receiver (Leica GR10 and AR10 radome antenna), a heading (±1°), pitch and roll (±0.1°) monitoring system, the power-supply monitoring of the overall system (current, voltage and PV panel’s power), and, for only-one of this, a meteorological station (air pressure and temperature, wind velocity and direction), an IP web-enabled camera (nel visibile), and a pulsed K-band radar tide-gauge. Each seafloor modules is equipped with a Bottom Pressure Recorder (Paroscientific, 8CDP-130I), a low-frequency and broad-band Hydrophones, a tri-axial broad-band (120s ÷ 25Hz) Ocean Bottom Seismometer with auto-leveling system, a tri-Axial Micro Electro-Mechanical Systems accelerometer (DC ÷ 100Hz), the clock synchronization (1PPS and NMEA) with absolute GPS time reference on RS-422 interface, a heading, pitch and roll monitoring system, the power-supply monitoring system (current, voltage, water detector and on-off power control), and, for only-one of this, a 3-D Current-meter with water temperature sensor . Recently, a sea floor borehole precision tiltmeter (LILY, Jewell Instruments) has been installed to extend to the Gulf of Pozzuoli the on land tiltmeter network. The overall marine monitoring research infrastructure therefore acquires 152+ channels with sampling frequencies variable from 60 seconds to 200 Hz. All the data are stored in a relational database and the complete time series are visible on a dedicated website, where all data can be downloaded as files, in various formats available.