http://hdl.handle.net/2122/229 Fri, 24 May 2013 17:55:04 GMT 2013-05-24T17:55:04Z http://hdl.handle.net/2122/8700 Title: Magnetic anomalies of steel drums: a review of the literature and research results of the INGV Authors: Marchetti, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Sapia, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Settimi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: The detection and evaluation of the status of disposal sites that contain hazardous waste materials is becoming an increasingly important element in environmental investigations. Close cooperation between the Istituto Nazionale di Geofisica e Vulcanologia (INGV; National Institute of Volcanology and Geophysics) in Rome and the Italian environmental police has resulted in numerous underground investigations of different buried materials. Among the geophysical investigation tools, magnetometry is the most effective, rapid and precise of all of the geophysical methods for localizing buried steel drums. Analysis of magnetic map anomalies can provide a variety of information about buried materials, including extension, distribution and depth, with processing of the acquired magnetic data. This information is also very useful in case of excavations that are aimed at the recovery of hazardous waste. This study determines the most relevant analyses reported in the literature, with modeling of magnetometric methods for environmental applications both theoretically and experimentally. Some studies and research results achieved by the INGV in relation to magnetic anomalies produced by buried steel drums are also reported, as found in field operations and as achieved from test sites. Thu, 18 Apr 2013 22:00:00 GMT http://hdl.handle.net/2122/8700 2013-04-18T22:00:00Z http://hdl.handle.net/2122/8620 Title: Italian Magnetic Network and Geomagnetic Field Maps of Italy at year 2010.0 Authors: Dominici, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Meloni, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Sperti, M.; Istituto Geografico Militare, Firenze; Manzo, G.; Istituto Geografico Militare, Firenze; Maseroli, R.; Istituto Geografico Militare, Firenze Abstract: In the frame of a long-time collaboration between INGV (Istituto Nazionale di Geofisica e Vulcanologia) and IGMI (Istituto Geografico Militare Italiano), also in the years 2009 and 2010 a survey of 131 repeat stations of the Italian Magnetic Network (including 2 observatories, 11 stations in Albania and 3 in Corsica and 1 in Malta) was carried out. In this paper the procedures for magnetic measurements and data elaboration are described. Furthermore, for all the repeat stations data reduced at of the measurement day, at the epoch 2010.0; are presented. At the same epoch the coefficients for normal fields were determined for all the data, in order to draw the new maps of the geomagnetic field elements (D, H, Z and total field F) at the year 2010.0, at 1: 2 000 000 scale. All these maps were created by mean of interpolation procedures on GIS platform. Sat, 31 Dec 2011 23:00:00 GMT http://hdl.handle.net/2122/8620 2011-12-31T23:00:00Z http://hdl.handle.net/2122/8591 Title: Italian Magnetic Network and magnetic reference fields at 2010.0 Authors: Dominici, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Meloni, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Di Ponzio, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Miconi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: The Istituto Nazionale di Geofisica e Vulcanologia (INGV) has systematically undertaken the task of making measurements of the Earth's magnetic field in Italy. By tradition and because of the elongated geometric shape of our peninsula and islands, in Italy, a grid of more than 110 points, called the first order repeat stations, with an average spacing around 55-60 km, is in operation. Over this grid the measurements are repeated regularly, every 5 years. A survey of 131 repeat stations of the Italian Magnetic Network (including 2 observatories, 11 stations in Albania, 3 stations in Corsica and 1 in Malta) was carried out between 2009 and 2010 with the main purpose of updating our magnetic cartography. We describe the characteristics of magnetic first and second order networks, the magnetic measurements and the data reduction procedure. In agreement with the recommendations of MagNetE Committee, we report new repeat station data measured and reduced at 2010.0. An analytical expression, a second order polynomial, in latitude and longitude for the field elements, was determined, and coefficients for 2010.0 and average secular variation over the period 2005-2010, were obtained. The new maps for Italy, for D, F, H and Z at the epoch 2010.0, are shown. A selection of stations from the Italian Magnetic Network, based on their low values of anomaly with respect to a 'normal' field, is also proposed for future surveys. Sat, 31 Dec 2011 23:00:00 GMT http://hdl.handle.net/2122/8591 2011-12-31T23:00:00Z http://hdl.handle.net/2122/8578 Title: Caratterizzazione del rumore magnetico di fondo nel nuovo osservatorio di Varese Ligure Authors: Palangio, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Carmisciano, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Di Lorenzo, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: The accuracy of geomagnetic field measurement at a given point on the Earth's surface is limited by the ambient magnetic noise level which is usually determined by the superposition of signals generated from different sources. The noise that dominates in all physical systems, particularly in spectral regions at lowest frequencies is the flicker noise [Vladimirov and Kleimenova 1962]. The analysis of the background noise that exists on the site is essential to design a new magnetic Observatory. Noise measurements allow then to evaluate the magnetic pollution status of the area and constitute a basic cognitive tool for the building of a new magnetic Observatory. Only by comparing signals of natural origin and the noise is possible to characterize the site. The purpose of this note is the separation of local and regional magnetic noise from signals of external origin. In the near field zone gradients are very high, the contribution of these sources depends much on the source-observer distance. Mon, 31 Dec 2012 23:00:00 GMT http://hdl.handle.net/2122/8578 2012-12-31T23:00:00Z http://hdl.handle.net/2122/8472 Title: ON THE PRESUMED ULF MAGNETIC PRECURSORS OF EARTHQUAKES Authors: Masci, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: During the last twenty years many researchers investigated ULF (Ultra-Low- Frequency) magnetic data in the hope of finding seismogenic signals. After the report of Fraser- Smith et al. (1990) several ULF stations were installed and many papers documented the observations of pre-earthquake magnetic anomalies. These claims motivate the belief that one day short-term earthquake prediction based on magnetic data may become a routine technique. Shortterm earthquake prediction has been the topic of several scientific debates but at present the entire subject remains still controversial. In order to be useful, short-term prediction requires reproducible earthquake precursors which provide information regarding intensity, location and time of the predicted earthquake together with error estimates for each parameter. Thus, a serious problem concerns the identification of reliable earthquake precursors. Recently, some researchers have given rise to a re-examination process of dubious earthquake precursors and published their findings. For example Masci (2010, 2011a), by means of global geomagnetic Kp index time-series, demonstrated that many presumed magnetic seismogenic signatures are not related to the subsequent earthquakes but are normal variations driven by the geomagnetic activity level. More precisely, as pointed out by Masci (2011a, 2012a), since the Kp index is representative of the geomagnetic field average disturbances over planetary scale, we should not expect that a good correlation between an ULF parameter of the geomagnetic field and Kp will always and everywhere exist during a long-time range. On the contrary, if a close correspondence between these changes of an ULF geomagnetic field parameter and Kp exists during a period of time, this indicates that the changes are part of normal global geomagnetic field variations driven by solar-terrestrial interactions and cannot be described as earthquake-related signals. Here, some examples of questioned earthquake precursors are reported hoping to shed light on the usefulness of the ULF magnetic measurements to study the occurrence of pre-earthquake seismogenic signals. In addition, the results of the analysis of magnetic data from the Geomagnetic Observatory of L’Aquila during the period of the 2009 L’Aquila seismic sequence are reported as well. Mon, 19 Nov 2012 23:00:00 GMT http://hdl.handle.net/2122/8472 2012-11-19T23:00:00Z http://hdl.handle.net/2122/8361 Title: New archeomagnetic and 226Ra-230Th dating of recent lavas for the Geological map of Etna volcano Authors: Tanguy, J.-C.; Condomines, M.; Branca, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; La Delfa, S.; Coltelli, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia Abstract: This work deals with the dating of Mount Etna lava flows and eruptive fissure deposits to the last four millennia following field investigations and stratigraphic data (BRANCA et alii, 2011a). We have studied 24 of these volcanic products, including 301 large samples, through high precision archeomagnetic dating checked by 226Ra-230Th radiochronology, thus providing additional material to the previous paper by TANGUY et alii (2007). In most cases our results allow attributing ages to the historical period, although two flows are shown to be prehistoric. For the historic lavas, archeoma - gnetic ages can be defined within decades, except for three of them that erupted during a time span (Greco-Roman epoch) when the geomagnetic field underwent little variation. Although 60% of these volcanics exhibit ages comprised between 700 AD and 1850, only one (1285) is mentioned by contemporary written accounts. We conclude that i) historical documents alone are insufficient to reconstruct a coherent sequence of eruptions, and ii) a multidisciplinary approach is necessary to obtain a comprehensive eruptive history of such a very active volcano, useful for both scientific and civil protection purposes, even for such a geologically recent period as that of the last 10 or 20 centuries. Thanks to these new archeomagnetic and 226Ra-230Th data coupled with stratigraphic data, a comprehensive volcanic history of the still-outcropping Mount Etna volcanics is now available for the last 2,400 years. Sat, 31 Dec 2011 23:00:00 GMT http://hdl.handle.net/2122/8361 2011-12-31T23:00:00Z http://hdl.handle.net/2122/8072 Title: Flank instability structure of Mt. Etna inferred by a magnetotelluric survey Authors: Siniscalchi, A.; Dipartimento di Scienze della Terra e Geoambientali, Università di Bari, Bari, Italy; Tripaldi, S.; Dipartimento di Scienze della Terra e Geoambientali, Università di Bari, Bari, Italy; Neri, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Balasco, M.; Istituto di Metodologie per l’Analisi Ambientale, Consiglio Nazionale delle Ricerche, Tito, Potenza, Italy; Romano, G.; Dipartimento di Scienze della Terra e Geoambientali, Università di Bari, Bari, Italy; Ruch, J.; Dipartimento di Scienze Geologiche, Università di Roma Tre, Rome, Italy; Schiavone, D.; Dipartimento di Scienze Geologiche, Università di Roma Tre, Rome, Italy Abstract: This paper presents a magnetotelluric (MT) survey of the unstable eastern flank of Mt. Etna. We take thirty soundings along two profiles oriented in the N-S and NW-SE directions, and from these data recover two 2D resistivity models of the subsurface. Both models reveal three major layers in a resistive-conductive-resistive sequence, the deepest extending to 14 km bsl. The shallow layer corresponds to the volcanic cover, and the intermediate conductive layer corresponds to underlying sediments segmented by faults. These two electrical units are cut by E-W-striking faults. The third layer (basement) is interpreted as mainly pertinent to the Apennine-Maghrebian Chain associated with SW-NE-striking regional faults. The detailed shapes of the resistivity profiles clearly show that the NE Rift is shallow-rooted ( 0–1 km bsl), thus presumably fed by lateral dikes from the central volcano conduit. The NW-SE profile suggests by a series of listric faults reaching up to 3 km bsl, then becoming almost horizontal. Toward the SE, the resistive basement dramatically dips (from 3 km to 10 km bsl), in correspondence with the Timpe Fault System. Several high-conductivity zones close to the main faults suggest the presence of hydrothermal activity and fluid circulation that could enhance flank instability. Our results provide new findings about the geometry of the unstable Etna flank and its relation to faults and subsurface structures. Thu, 29 Mar 2012 22:00:00 GMT http://hdl.handle.net/2122/8072 2012-03-29T22:00:00Z http://hdl.handle.net/2122/8037 Title: The study of ionospheric anomalies in Japan area during 1998–2010 by Kon et al.: An inaccurate claim of earthquake-related signatures? Authors: Masci, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: The problem of identifying precursory signals of earthquakes in the hope of mitigate the seismic hazard is a very important topic, but inaccurate documentations of precursory signatures decrease the credibility of this field of research. The statistical analysis by Kon et al. (2011) shows that there is tendency of positive total electron content (TEC) anomalies to occur 1–5 days before 52 M > 6 earthquakes which struck Japan during 1998–2010. Kon et al. (2011) also report in detail three selected case studies claiming the occurrence of TEC anomalies possibly related to large and destructive earthquakes. This paper casts doubts on the possibility that in the three cases the TEC disturbances were caused by seismic events suggesting that these TEC changes could be induced by normal variations of the global geomagnetic activity. As a consequence, also the results of the Superimposed Epoch Analysis performed by Kon et al. (2011) could be seriously influenced by global magnetospheric signals. Tue, 04 Sep 2012 22:00:00 GMT http://hdl.handle.net/2122/8037 2012-09-04T22:00:00Z http://hdl.handle.net/2122/8036 Title: Comment on ‘‘Possible association between anomalous geomagnetic variations and the Molise Earthquakes at Central Italy during 2002’’ by Takla et al. (2011) Authors: Masci, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: Takla et al. (2011) documented the observation of seismogenic precursory signals in the geomagnetic field components of L’Aquila station (LAQ) which occurred before the 2002 Molise earthquakes. Here, these claims are reviewed taking into account the geomagnetic index ΣKp time-series and by means of data coming from the Geomagnetic Observatory of L’Aquila where the LAQ station is located. This review shows that before the Molise earthquakes the anomalous behaviour of LAQ geomagnetic field components was actually caused by a possible thermal drift of the instrumentation. In conclusion there is no firm relation between the earthquakes occurrence and the observed magnetic anomalous signatures documented by Takla et al. (2011). Tue, 31 Jul 2012 22:00:00 GMT http://hdl.handle.net/2122/8036 2012-07-31T22:00:00Z http://hdl.handle.net/2122/8009 Title: Paleomagnetic secular variation at the Azores during the last 3 ka Authors: Di Chiara, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Speranza, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Porreca, M.; Centro de Vulcanologia e Avaliação de Riscos Geológicos, Universidade dos Açores, Ponta Delgada, Portugal. Abstract: We report on 33 new paleomagnetic directions obtained from 16 lava flows emplaced in the last 3 ka on São Miguel, the largest island of the Azores. The data provide 27 well-dated directions from historical or 14C dated flows which, together with 6 directions previously gathered from the same flows by Johnson et al. (1998), yield the first paleomagnetic directional record of the last 3 ka from the Atlantic Ocean. Within-flow directions are consistent, suggesting that inclination swings from 60 to 25 and declination changes between 10 to 20 reflect variations in the geomagnetic field over the last 3 ka. To a first approximation, the declination record is consistent with predictions from CALS3k.4 and gufm1 global field models. Conversely, inclination values are lower than model predictions at two different ages: 1) four sites from the 1652 AD flow yield I = 48 instead of I = 63 predicted by gufm1; 2) data from several flows nicely mimic the inclination minimum of 800–1400 AD, but inclination values are lower by 10 than CALS3k.4 model predictions. By interpolating a cubic spline fit on declination / inclination versus age data, we tentatively infer the directional evolution of the geomagnetic field at the Azores from 1000 BC to 1600 AD. The obtained curve shows three tracks in virtual overlap during the 1000–800 BC, 800–500 BC, and 400–700 AD time spans. Wed, 11 Jul 2012 22:00:00 GMT http://hdl.handle.net/2122/8009 2012-07-11T22:00:00Z