Four Years of Continuous Seafloor Displacement Measurements in the Campi Flegrei Caldera

We present 4 years of continuous seafloor deformation measurements carried out in the Campi Flegrei caldera (Southern Italy), one of the most hazardous and populated volcanic areas in the world. The seafloor sector of the caldera has been monitored since early 2016 by the MEDUSA marine research infrastructure, consisting of four instrumented buoys installed where sea depth is less than 100 m. Each MEDUSA buoy is equipped with a cabled, seafloor module with geophysical and oceanographic sensors and a subaerial GPS station providing seafloor deformation and other environmental measures. Since April 2016, the GPS vertical displacements at the four buoys show a continuous uplift of the seafloor with cumulative measured uplift ranging between 8 and 20 cm. Despite the data being affected by environmental noise associated with sea and meteorological conditions, the horizontal GPS displacements on the buoys show a trend coherent with a radial deformation pattern. We use jointly the GPS horizontal and vertical velocities of seafloor and on-land deformations for modeling the volcanic source, finding that a spherical source fits best the GPS data. The geodetic data produced by MEDUSA has now been integrated with the data flow of other monitoring networks deployed on land at Campi Flegrei

IXPE and XMM-Newton observations of the Soft Gamma Repeater SGR 1806-20

Recent observations with the Imaging X-ray Polarimetry Explorer (IXPE) of two anomalous X-ray pulsars provided evidence that X-ray emission from magnetar sources is strongly polarized. Here we report on the joint IXPE and XMM-Newton observations of the soft {\gamma}-repeater SGR 1806-20. The spectral and timing properties of SGR 1806-20 derived from XMM-Newton data are in broad agreement with previous measurements; however, we found the source at an all-time-low persistent flux level. No significant polarization was measured apart from the 4-5 keV energy range, where a probable detection with PD=31.6\pm 10.5% and PA=-17.6\pm 15 deg was obtained. The resulting polarization signal, together with the upper limits we derive at lower and higher energies 2-4 and 5-8 keV, respectively) is compatible with a picture in which thermal radiation from the condensed star surface is reprocessed by resonant Compton scattering in the magnetosphere, similar to what proposed for the bright magnetar 4U 0142+61.Comment: 11 pages, 3 figures, accepted for publication in Ap

XIPE: the x-ray imaging polarimetry explorer

XIPE, the X-ray Imaging Polarimetry Explorer, is a mission dedicated to X-ray Astronomy. At the time of writing XIPE is in a competitive phase A as fourth medium size mission of ESA (M4). It promises to reopen the polarimetry window in high energy Astrophysics after more than 4 decades thanks to a detector that efficiently exploits the photoelectric effect and to X-ray optics with large effective area. XIPE uniqueness is time-spectrally-spatially- resolved X-ray polarimetry as a breakthrough in high energy astrophysics and fundamental physics. Indeed the payload consists of three Gas Pixel Detectors at the focus of three X-ray optics with a total effective area larger than one XMM mirror but with a low weight. The payload is compatible with the fairing of the Vega launcher. XIPE is designed as an observatory for X-ray astronomers with 75 % of the time dedicated to a Guest Observer competitive program and it is organized as a consortium across Europe with main contributions from Italy, Germany, Spain, United Kingdom, Poland, Sweden

Un metalinguaggio versatile per strumentazione con interfaccia di comunicazione seriale

INGVPublished7TM. Sviluppo e Trasferimento Tecnologic

GAMbUSIA - a GenerAl purpose Metalanguage for instrUments with Serial InterfAce

Monitoring system designed for biological and marine environment observation are equipped with different types of sensors related to different disciplines. For each sensor integrated in the system it is necessary to develop a driver (software/firmware) specific to its operation. This kind of approach limits the system flexibility because the addition of a new sensor involves the update of the entire software control . For this reason it is important to reduce the time and simplify the work required to integrate new sensors. This paper present GAMbUSIA (GenerAl purpose Metalanguage for instrUments with Serial InterfAce) wich aim to improve code reuse and system flexibility. GAMbUSIA is a metalanguage, based on eXtensible Markup Language (XML), with which it is possible to describe the communication protocol at a high level and use (and reuse) this description instead to develop an ad-hoc driver. In order to evaluate the proposed solution, Gambusia is used to create an oceanographic sensor description in a data acquisition system.Published7TM. Sviluppo e Trasferimento TecnologicoJCR Journa

Misure di deformazione verticale sul fondo marino in acque costiere con sensore di pressione: applicazione all’area dei Campi Flegreii

The following work represents the first vertical deformation measurement of the ground in coastal waters obtained through the use of a BPR sensor (Bottom Pressure Recorder) installed in shallow water, with an accuracy comparable with that of the measures carried out by a GPS network placed on the mainland. The described measurement method allows the use of pressure sensors - based on quartz technology - as a possible and low cost integration, which allows the extension in the coastal waters of the geodetic monitoring networks located on the mainland. The area under investigation is the caldera of Campi Flegrei (Pozzuoli) in which even the bradyseism is continually monitored by the Vesuvius Observatory surveillance system in Naples. In the Gulf of Pozzuoli, which is the submerged part of the caldera, on-going studies are performing innovative methods for geophysical monitoring at sea bottom, and – in particular – vertical measures of the soil through the use of BPR sensors. Even in the shallow water condition, such as that of the Gulf of Pozzuoli, it is noted that the BPR can provide reliable estimates of vertical movements of the soil at sea bottom, through the correction of the pressure data with environmental data and it comparison with the sea level obtained from the tide gauge network. In the pages that follow, it provides guidance as to the real possibility to use BPR for the vertical movements measure of the ground, at speeds of a few centimetres per year, in the submerged part of an active volcanic area, where the sea depth does not exceed one hundred meters.INGVPublished1-203A. Geofisica marinaN/A or not JC

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

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.PublishedVienna3A. Geofisica marina e osservazioni multiparametriche a fondo mar

Hydrophone as an accelerometer

We present the equivalence of the ground acceleration and water pressure variation induced by earthquakes, using data from co-located seafloor instruments in shallow water. The equivalence is evident from a strong similarity of the waveforms, which completely and persistently overlap along the entire duration of the recordings, and it is supported by a high cross-correlation value. Moreover, the comparison of the amplitude spectra of the acceleration and pressure signals confirms the existence of a frequency range of ‘forced oscillations’, where the pressure variations are proportional to the ground vertical component of the acceleration. We demonstrate the equivalence of the signals for a set of local and regional earthquakes on a wide range of magnitude (2.7<M<6.8), recorded by seismometers and hydrophones operating in a coastal monitoring infrastructure, at less than 80 m of water depth, located in the Gulf of Pozzuoli (Campi Flegrei caldera, Southern Italy). The infrastructure consists of four marine platforms which integrate a wide set of sensors, in particular a seafloor multi-sensor module, hosting a broad-band seismometer (120s – 100 Hz), a low frequency hydrophone (down to 0.01 Hz) and a bottom pressure recorder. The simple linear relation between sea bottom pressure variation and vertical seafloor acceleration measurement is widely reported in the scientific literature and well verified in previous works. All these works use data from low frequency waveforms of large magnitude tsunamigenic earthquakes, recorded by pairs of bottom pressure recorders and accelerometers. Here, for the first time, short period data recorded by pairs of hydrophones and seismometers are used expanding the theory validity to a larger frequency range. The high correlation value between the ground acceleration, derived from the ground velocity, and hydrophone pressure signals allows to calibrate hydrophones by comparison with co-located accelerometers, or seismometers, used as a reference in a range of frequencies that is very difficult to reproduce in lab. The proved similarity of the recordings underpins the possibility that hydrophones can be more extensively used in place of accelerometers in those marine environment, where seismic sensor accurate installation is usually not easy and not always affordable.UnpublishedSan Francisco1IT. Reti di monitoraggio e sorveglianz

Measurement of Seafloor Deformation in the Marine Sector of the Campi Flegrei Caldera (Italy)

We present an assessment of vertical seafloor deformation in the shallow marine sector of the Campi Flegrei caldera (southern Italy) obtained from GPS and bottom pressure recorder (BPR) data, acquired over the period April 2016 to July 2017 in the Gulf of Pozzuoli by a new marine infrastructure, MEDUSA. This infrastructure consists of four fixed buoys with GPS receivers; each buoy is connected by cable to a seafloor multisensor module hosting a BPR. The measured maximum vertical uplift of the seafloor is about 4.2 ± 0.4 cm. The MEDUSA data were then compared to the expected vertical displacement in the marine sector according to a Mogi model point source computed using only GPS land measurements. The results show that a single point source model of deformation is able to explain both the GPS land and seafloor data. Moreover, we demonstrate that a network of permanent GPS buoys represents a powerful tool to measure the seafloor vertical deformation field in shallow water. The performance of this system is comparable to on-land high-precision GPS networks, marking a significant achievement and advance in seafloor geodesy and extending volcano monitoring capabilities to shallow offshore areas (up to 100 m depth). The GPS measurements of MEDUSA have also been used to confirm that the BPR data provide an independent measure of the seafloor vertical uplift in shallow water.Published66-834V. Processi pre-eruttiviJCR Journa