http://hdl.handle.net/2122/233 2013-05-17T06:51:19Z 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. 2013-04-18T22:00:00Z http://hdl.handle.net/2122/8504 Title: Further comments on the ionospheric precursor of the 1999 Hector Mine earthquake Authors: Masci, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: Pulinets et al. (2007) document anomalous changes in the ionospheric total electron content (TEC) starting one week before the 16 October 1999 Hector Mine earthquake. The authors maintain that this TEC anomalous change is a precursor of the subsequent earthquake. In a previous paper, Afraimovich et al. (2004) excluded that TEC variations, which occurred before the Hector Mine earthquake, were induced by the preparation process of the seismic event. Thomas et al. (2012) reach similar conclusions by performing new analyses of the same TEC data which were investigated by Pulinets et al. (2007). They show that the TEC changes documented by Pulinets et al. (2007) are not anomalous but normal variations on global scale, and, therefore, these changes are not related to the localised seismic activity of the Hector Mine area. This paper confirms the results of Afraimovich et al. (2004) and Thomas et al. (2012). Through the use of geomagnetic indices time series it is shown that the presumed precursor of Pulinets et al. (2007) was a normal TEC variation induced by solar-terrestrial interaction. 2013-01-28T23:00:00Z http://hdl.handle.net/2122/8503 Title: On the multi-fractal characteristics of the ULF geomagnetic field before the 1993 Guam earthquake Authors: Masci, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: Ida et al. (2005) document significant changes in the multi-fractal parameters of the ULF geomagnetic field H component starting about one month before the 1993 Guam earthquake. According to the authors, these multi-fractal signatures can be considered as precursory signals of the Guam earthquake. As a consequence, they conclude that the multifractal analysis may have an important role in the development of short-term earthquake prediction capabilities. Since this and other similar reports have motivated the idea that earthquake prediction based on electromagnetic precursory signals may one day become a routine technique, the presumed precursors need to be validated through independent datasets. In this review the seismogenic origin of the multifractal magnetic signatures documented by Ida et al. (2005) before the 8 August 1993 Guam earthquake is seriously put into question. By means of the geomagnetic ΣKp index, it is demonstrated that these multi-fractal parameter changes are normal signals induced by the variation of the global geomagnetic activity level. 2013-01-28T23:00:00Z http://hdl.handle.net/2122/8476 Title: The Ionian Sea:The oldest in situ ocean fragment of the world Authors: Speranza, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Minelli, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Pignatelli, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Chiappini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: It is well known that the Ionian Sea is characterized by thin (8-11 km) crystalline crust, thick (5-7 km) sedimentary cover, and low heat flow, typical for a Mesozoic (at least) basin. Yet seismic data have not yielded univocal interpretations, and a debate has developed on the oceanic vs. “thinned continental” nature of the Ionian basin. Here we analyze the magnetic anomaly pattern of the Ionian Sea, and compare it to synthetic fields produced by a geopotential field generator, considering realistic crust geometry. The Ionian basin is mostly characterized by slightly negative magnetic residuals, and by a prominent positive (150 nT at sea level) “B” anomaly at the northwestern basin margin. We first test continental crust models, considering a homogeneous crystalline crust with K=1x10-3, then a 5 km thick deep crustal layer of serpentinite (K=1x10-1). First model yields insignificant anomalies, while the second gives an anomaly pattern anti-correlated with the observed residuals. We subsequently test oceanic crust models, considering a 2 km thick 2A basaltic layer with K=5x10-3, magnetic remanence of 5 A/m, and a unique magnetic polarity (no typical oceanic magnetic anomaly stripes are apparent in the observed data set). Magnetic remanence directions were derived from Pangean-African paleopoles in the 290-190 Ma age window. Only reverse-polarity models reproduce the B anomaly, and among them the 220-230 Ma models best approximate magnetic features observed on the abyssal plain and at the western basin boundary. The Ionian Sea turns out to be the oldest preserved oceanic floor known so far. 2011-12-31T23:00:00Z 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. 2012-11-19T23:00:00Z http://hdl.handle.net/2122/8040 Title: Marine Archaeogeophysical Prospection of Roman Salapia Settlement (Puglia, Italy): Detecting Ancient Harbour Remains Authors: Cocchi, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Stefanelli, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Carmisciano, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Caratori Tontini, F.; GNS Sciense, New Zealand; Taramaschi, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cipriani, S.; Provincia della Spezia Abstract: The Gulf of Manfredonia and the Tavoliere Plain have experienced intense human colonization since the neolithic times. There is past evidence in the study area of a Roman-age settlement historically known as Salapia, probably located close to the salt-production ponds. In particular, several portions of a partly submerged ancient pier-like structure were found close to Torre Pietra town. This structure has been interpreted as a portion of a dragged-ship channel that connected the town of Salapia to the sea. In this article we discuss the results of a high-resolution geophysical prospecting of the Margherita di Savoia offshore archaeological site (Puglia, Italy). We collected magnetic gradiometric and bathymetric data to map the submerged remains of Salapia harbour. We found evidence of an offshore projection of a Torre Pietra pier-like structure, identifying the direction of the ship channel and possibly the location of the harbour’s defensive post 2012-01-31T23:00:00Z http://hdl.handle.net/2122/8039 Title: Magnetic and seismic reflection study of Lake Cheko, a possible impact crater for the 1908 Tunguska Event Authors: Gasperini, L.; CNR-Ismar Bologna; Cocchi, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Stanghellini, C.; INAF-Bologna; Stanghellini, G.; CNR-Ismar Bologna; Del Bianco, F.; CNR-Ismar Bologna; Serrazanetti, M.; CNR-Ismar Bologna; Carmisciano, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: A major explosion occurred on 30 June 1908 in the Tunguska region of Siberia, causing the destruction of over 2,000 square km of taiga; pressure and seismic waves detected as far as 1,000 km away; bright luminescence in the night skies of Northern Europe and Central Asia; and other unusual phenomena. This “Tunguska Event” is probably related to the impact with the Earth of a cosmic body that exploded about 5-10 km above ground, releasing in the atmosphere 10-15 Mton of energy. Fragments of the impacting body have never been found, and its nature (comet or asteroid) is still a matter of debate. We report here results from a magnetic and seismic-reflection study of a small (~500 m diameter) lake, Lake Cheko, located about 8 km NW of the inferred explosion epicenter, that was proposed to be an impact crater left by a fragment of the Tunguska Cosmic Body. Seismic-reflection and magnetic data revealed a P-wave velocity/magnetic anomaly close to the lake center, about 10 m below the lake floor; this anomaly is compatible with the presence of a buried stony object and supports the impact crater origin for Lake Cheko. 2012-05-11T22:00:00Z 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. 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). 2012-07-31T22:00:00Z http://hdl.handle.net/2122/8034 Title: Birth of an ocean in the Red Sea: Initial pangs Authors: Ligi, M.; CNR-ISMAR Bologna; Bonatti, E.; CNR-ISMAR Bologna; Bortoluzzi, G.; CNR-ISMAR Bologna; Cipriani, A.; CNR-ISMAR Bologna; Cocchi, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Caratori Tontini, F.; GNS Science; Carminati, E.; Università di Roma "La Sapienza"; Ottolini, L.; CNR -Pavia; Schettino, A.; Università di Camerino Abstract: We obtained areal variations of crustal thickness, magnetic intensity, and degree of melting of the sub- axial upwelling mantle at Thetis and Nereus Deeps, the two northernmost axial segments of initial oceanic crustal accretion in the Red Sea, where Arabia is separating from Africa. The initial emplacement of oceanic crust occurred at South Thetis and Central Nereus roughly $2.2 and $2 Ma, respectively, and is taking place today in the northern Thetis and southern Nereus tips. Basaltic glasses major and trace element com- position suggests a rift-to-drift transition marked by magmatic activity with typical MORB signature, with no contamination by continental lithosphere, but with slight differences in mantle source composition and/or potential temperature between Thetis and Nereus. Eruption rate, spreading rate, magnetic intensity, crustal thickness and degree of mantle melting were highest at both Thetis and Nereus in the very initial phases of oceanic crust accretion, immediately after continental breakup, probably due to fast mantle upwelling enhanced by an initially strong horizontal thermal gradient. This is consistent with a rift model where the lower continental lithosphere has been replaced by upwelling asthenosphere before continental rupturing, implying depth-dependent extension due to decoupling between the upper and lower lithosphere with man- tle-lithosphere-necking breakup before crustal-necking breakup. Independent along-axis centers of upwell- ing form at the rifting stage just before oceanic crust accretion, with buoyancy-driven convection within a hot, low viscosity asthenosphere. Each initial axial cell taps a different asthenospheric source and serves as nucleus for axial propagation of oceanic accretion, resulting in linear segments of spreading. 2012-08-17T22:00:00Z