IMPIEGO DELL’INTERFEROMETRIA A LARGA BANDA NELLO STUDIO DEI SEGNALI ELETTROMAGNETICI DI ORIGINE INTERNA ALLA TERRA NEL PROGETTO FIRB-ABRUZZO

Il terremoto di L’Aquila del 2009 ci ha resi consapevoli che occorre fare un salto qualitativo nella osservazione dei campi magnetici naturali se vogliamo estendere le nostre indagini ai fenomeni elettromagnetici che accompagnano in generale i processi geodinamici (Palangio et al., 2008). Questo terremoto è l’unico nella storia che si sia verificato praticamente sotto un osservatorio geomagnetico con 50 anni di storia. La disponibilità di un così esteso archivio dati ci consente di monitorare tutta la fase preparatoria finale del terremoto. Stando alla letteratura corrente avremmo dovuto osservare effetti cosismici molto intensi, invece i segnali osservati lambiscono appena la superficie del mare di noise in cui sono immersi (Palangio et al., 2007) soltanto in alcune bande di frequenza i segnali ipogeici emergono nettamente dal rumore di fondo (Di Lorenzo et.al., 2011). Da questa esperienza del terremoto di L’Aquila è emersa la necessità di progettare un sistema osservativo che consenta di rilevare “l’impronta” del terremoto nei segnali elettromagnetici misurati sulla superficie terrestre. Questa impronta dovrebbe fornire la prova del legame tra il fenomeno tettonico e il campo magnetico osservato. Lo studio dei segnali magnetici prima e durante la fase sismica di L’Aquila ha messo in luce alcuni aspetti interessanti che riguardano il rumore di fondo e le finestre spettrali e temporali di osservabilità degli eventuali segnali magnetici di origine interna alla terra legati al terremoto

A long term geomagnetic deep sounding analysis from a two-dimensional magnetometer array in Central Italy

Abstract Following the Mw 6.3 earthquake that hit the city of L'Aquila (Central Italy) on the 6th April 2009, a scientific project was proposed with the aim of investigating the Abruzzo area by means of different disciplinary approaches including geological, seismic, and physical studies. Electromagnetic field monitoring in the 0.01–500 mHz frequency band was implemented for the investigation of electromagnetic signals in the Earth's crust. Three measurement stations were installed in a tectonically active area with a radius of about 10 km. Each site was equipped with a fluxgate magnetometer with a 1 Hz sampling rate. This paper describes a long term geomagnetic deep sounding analysis for each site, aimed at investigating the dimensionality of the electrical structure of the subsurface in the area involved in the survey. According to a very simplified RL circuit model, some electrical properties of subsurface are also deduced

Misure curlometriche nei fondali marini

Nei fondali marini in cui sono presenti discontinuità nelle proprietà fisico-chimiche quali ad esempio giacimenti minerari o di combustibili naturali [1] oppure discontinuità tettoniche si possono generare correnti elettriche che si chiudono in parte attraverso l'acqua del mare elettricamente molto conduttiva e in parte nel sottosuolo marino. Inoltre sono presenti anche correnti elettriche indotte dalle variazioni del campo magnetico e correnti generate per effetto MHD dal moto dell'acqua. In generale il campo magnetico misurato al di fuori del sistema di correnti che lo generano gode di due fondamentali proprietà: è indivergente e irrotazionale [5]. All'interno delle sorgenti il rotore del campo magnetico è legato alle correnti e quindi al campo elettrico, mentre la divergenza è legata alla presenza di pozzi o sorgenti di corrente o a gradienti non lineari del campo magnetico. In questo lavoro si propone il rilevamento del campo magnetico e delle correnti nei fondali marini mediante misure dirette della divergenza e del rotore del campo magnetico locale

Investigations on diurnal and seasonal variations of Schumann resonance intensities in the auroral region

Measurements of the magnetic component of the Schumann resonance in the frequency range 6-14 Hz were performed at high latitude location (TNB Antarctica; geographic coordinates: 74.7°S, 164.1°E; geomagnetic coordinates: 80.0°S, 307.7°E; LT=UT+13; MLT=UT8; altitude=28 m a.s.l.), during the two years 1996-1997. TNB is a particularly important observation site located in a region characterised by a high electromagnetic activity in the ELF and VLF bands. Moreover its remote location in Antarctica provides the important advantage that electromagnetic background noise is not corrupted by anthropogenic noise and that the continental lightning activity is very low. The combination of low additional anthropogenic electromagnetic radiation and low atmospheric noise in this area allows detailed investigations into wave generation and amplification in the polar ionosphere and magnetosphere not possible anywhere else in the world. This paper reports the study of the magnetic power of the 8 Hz Schumann resonance mode. For both the years considered diurnal and long-term seasonal variations were observed

Seismic rotation waves: basic elements of theory and recording

Returning to the old problem of observed rotation effects, we present the recording system and basic elements of the theory related to the rotation fi eld and its association with seismic waves. There can be many different causes leading to observed/recorded rotation effects; we can group them as follows: generation of micro-displacement motion due to asymmetry of source processes and/or due to interaction between seismic body/surface waves and medium structure; interaction between incident seismic waves and objects situated on the ground surface. New recording techniques and advanced theory of deformation in media with defects and internal (e.g., granular) structure make it possible to focus our attention on the fi rst group, related to microdisplacement motion recording, which includes both rotation and twist motions. Surface rotations and twists caused directly by the action of emerging seismic waves on some objects situated on the ground surface are considered here only in the historical aspects of the problem. We present some examples of experimental results related to recording of rotation and twist components at the Ojcow Observatory, Poland, and L'Aquila Observatory, Italy, and we discuss some prospects for further research

Tectonomagnetic and VLF electromagnetic signals in Central Italy

Tectonomagnetic field observations from absolute magnetic field level measurements were undertaken in Central Italy in an area extending between latitude 41°N and 43°N and between longitude 13°E and 15°E. Moreover,natural electromagnetic signals from a system of two VLF search coil wide-band antennas were collected at the geomagnetic observatory of L Aquila (42º23'N, 13º19'E). The analysis of these data allowed the investigation of the electromagnetic properties of the study area at different time and spatial lengthscales. Tectonomagnetic field observations were obtained comparing data simultaneously recorded at three magnetometer stations using L'Aquila Observatory as a reference for differentiation. We report on the time evolution of magnetic and electromagnetic indicators related to local and regional seismic activity

Update on monitoring of magnetic and electromagnetic tectonic signals in Central Italy

A network of three absolute magnetometer stations and the geomagnetic observatory of LAquila (42°23N, 13°19E) monitors possible seismo- or tectonomagnetic effects in Central Italy, using LAquila Observatory as a reference for differentiation. A system of two VLF search coil wide-band antennas, working in two different frequency bands, at the LAquila Observatory, monitors possible electromagnetic effects related to seismic events occurring in Central Italy. Absolute magnetic field observations and VLF signals have been collected for several years. In particular the tectono-magnetic network started its operations in 1989. In this paper we report on the time variation of above mentioned data for the most recent years 2002 and 2003, also in connection with older measurements time series; we also report on seismic activity recorded in this area by the national seismic network. In the above mentioned time interval, no strong earthquake activity was recorded, and at the same time no clear evidence for magnetic or electromagnetic signals related to seismic events was found

Fourteen years of geomagnetic daily variation at Mario Zucchelli Station (Antarctica)

During the 1986-87 austral summer a geomagnetic observatory was installed at the Italian Antarctic Base Mario Zucchelli Station. In the first three years continuous time variation monitoring and absolute measurements of the geomagnetic field were carried out only during summer expeditions. Starting 1991 an automatic acquisition system, operating through all the year, was put in operation. We present here some peculiarities of the daily variation as observed for fourteen years (1987-2000). The availability of a long series of data has allowed the definition of seasonal, as well as solar cycle effects, on short time variations as observed at a cusp-cap observatory. In particular, contrary to mid latitude behaviour, a clear dependence of the daily variation amplitude on the global geomagnetic K index was well defined

Pegaso: an ultra-light long duration stratospheric

Launched from the Mario Zuccelli Station (Baia Terra Nova) in Antarctica during the 2005/06 austral summer, the PEGASO-D payload lifted into the stratospheric anticyclone over the southern polar region. This effort marks the first Long Duration Scientific payload to be launched from this location and is the fourth such payload launched in the polar regions. Performing in the framework of the NOBILE/AMUNDSEN collaborative LDB development between ASI-ARR. The Italian Institute of Geophysics and Volcanology (INGV), with the sponsorship of the Italian Antarctic Program (PNRA) and the Italian Space Agency (ASI),designed and built the Ultra-Light system together with three Universities in Italy. The Pegaso program has been created to investigate the Earth magnetic field and provide a precursor series of small payload launches for the bigger LDB program such as OLIMPO, BOOMERanG and BArSPOrt through this collaboration between ASI and ARR. The Italian scientific community, aware of the big advantages that LDB balloons can offer to their experiments, proposed to extend the LDB program to Southern polar regions, besides performing launches from the newly initiated Nobile/Amundsen Stratospheric Balloon Center in Svalbard, Norway.Three PEGASO (Polar Explorer for Geomagnetics And other Scientific Observations) payloads have been launched from the Svalbard (No) in collaboration with Andoya Rocket Range, ASI and ISTAR (Operations and logistics) during the past two northern summers. These stratospheric (altitude m.35000) small 10kmc balloons have floated in the stratosphere between 14 to 39 days measuring the magnetic field of polar regions, by means of a 3-axys-fluxgate magnetometer, during a three year campaign. The study of the magnetic field and its variations is done through permanent observatories. They provide us with high quality data but their spatial distribution is not quite regular, specially in Antarctica due to logistic difficulties. The coverage is improved through marine and aeromagnetic surveys, and also through satellite missions. There exists nevertheless a gap in the wavelengths of the magnetic field represented by these kind of measurements. Satellite data are too far away from Earth's surface to individuate wavelengths lower than 1000 km, and near-ground sur- veys are not able to represent wavelengths longer than the dimensions of the surveyed area. Moreover, there is a region empty of data around the geographical pole for the satellite measurements. The size of these gaps depends on the orbital parameters, but it can reach up to 10 degrees around the pole. PEGASO allows to bridge this gap in the measurements of the magnetic field. Surveys carried out at 35 km height allow the study of crustal anomalies in the range between, we can say, 60 and 1000 km. Taking into account that pathfinders (smaller non-recoverable balloon systems) are usually sent to explore the atmospheric currents, the use of PEGASO as pathfinder allows us to obtain all these results at a very affordable cost. The PEGASO payload was also developed as a single source system integrating science, housekeeping and operational control of the entire balloon borne configuration.Satellite telemetry sent the scientific (magnetometric) data, house-keeping (temperature, solar panel voltage and current, altitude and time) and telecommand (four ballast, two parachute release system, system reset), and powered the terminate system. Data flows through the IRIDIUM telephone service. The onboard systems were kept inside a vessel (white painted and pressurizzed vessel due to power dissipation) except for external flexible solar panels and magnetometer, attached to an external boom. Two redundant tracking systems have been used: a first GPS was integrated inside the on-board telemetry system, necessary to reconstruct position and time of scientific data, while an independent GPS-ARGOS system gave the balloon trajectory, including its descent. Continuous trajectory predictions were made during the missions; they have been necessary, in particular, for the flight safety requirements of the northern hemisphere. The evaluation of the statistical error is proposed. The PEGASO payload was developed to be a light, cost effective way to explore the potential of Ultra-Light Long Duration Ballooning for science as well as an introduction to the earth-space possibilities for students.PublishedBeijing, China1A. Geomagnetismo e Paleomagnetism

The Structure of the Big Magnetic Storms

The records of geomagnetic activity during Solar Cycles 22 and 23 (which occurred from 1986 to 2006) indicate several extremely intensive A-class geomagnetic storms. These were storms classified in the category of the Big Magnetic Storms. In a year of maximum solar activity during Solar Cycle 23, or more precisely, during a phase designated as a post-maximum phase in solar activity (PPM – Phase Post maximum), near the autumn equinox, on 29, October 2003, an extremely strong and intensive magnetic storm was recorded. In the first half of November 2004 (7, November 2004) an intensive magnetic storm was recorded (the Class Big Magnetic Storm). The level of geomagnetic field variations which were recorded for the selected Big Magnetic Storms, was ΔDst > 350 nT. For the Big Magnetic Storms the indicated three-hour interval indices geomagnetic activity was Kp = 9. This study presents the spectral composition of the Di – variations which were recorded during magnetic storms in October 2003 and November 2004