Options
Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione Roma2, Roma, Italia
Loading...
Country
IT
City
Roma
Description
INGV Institute
2835 results
Now showing 1 - 10 of 2835
- PublicationOpen AccessEvidence for a geomagnetic jerk in 1990 across Europe(1995-09)
; ; ;Cafarella, L.; Istituto Nazionale di Geofisica, Roma, Italy ;Meloni, A.; Istituto Nazionale di Geofisica, Roma, Italy; The analysis of geomagnetic data from magnetic observatories demonstrated the existence of very rapid changes, or jerks, in the secular variation, especially the occurrence of the well known geomagnetic jerks of 1969 and 1978. A new geomagnetic jerk seems to have appeared around 1990 and is clearly visible at a selec- tion of European magnetic observatories as a rapid and sudden change in the secular variation pattern. The comparison between all day and quiet day means for two different observatories, respectively at high and middle latitude, suggests that this phenomenon, as stated by many authors for the other jerks, could be generated by an internal source. - PublicationRestrictedMicrobial vs abiotic origin of methane in continental serpentinized ultramafic rocks: A critical review and the need of a holistic approachContinental ultramafic rock systems, through the process of serpentinization, provide chemical and biochemical pathways that lead to the production of methane. The extent to which rock-water-gas reactions and organisms supply methane in these systems is a matter of considerable discussion and debate. Deciphering the interplay of abiotic and microbial methane observed at the surface requires several lines of reasoning as well as a variety of analyses. Despite using multiple models and interpretative tools, conclusions for the origin of methane at a particular site may vary or diverge from regional or global observations. Here, we critically address how possible conclusions of microbial versus abiotic methane in continental serpentinization systems may be interpreted and reinterpreted. We review fundamental concepts, advantages and limits, for three major methane origin models: (a) abiotic CO2 hydrogenation supplying gas reservoirs, (b) derivation from fluid inclusions in olivine-rich rocks, and (c) microbialgenesis in aquifers. We use the case of methane in the Samail ophiolite of Oman as an emblematic example of multiple interpretations; we identify ambiguous information offered by methane clumped isotopes and molecular gas compositions (e.g., the meaning of gaseous hydrocarbons heavier than methane), and suggest key tools, such as radiocarbon (14C) in methane, which may solve interpretative issues. The major constraint in any model of methane origin is the capability to sustain continuous gas flows, in terms of methane emission intensity, longevity and spatial extension, such as in natural gas sedimentary systems. Overall, this review suggests that any site interpretation can benefit from a holistic approach, integrating geochemical, geological and biological data with gas flow dynamics, as well as including regional and global contextualization.
53 17 - PublicationRestrictedStrato-mesospheric ozone measurements using ground-based millimeter-wave spectroscopy at Thule, Greenland(2012-04-13)
; ; ; ; ; ; ;Muscari, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Cesaroni, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Fiorucci, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Smith, A. K.; Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado, USA ;Froidevaux, L.; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA ;Mlynczak, M. G.; NASA Langley Research Center, Hampton, Virginia, USA; ; ; ; ; On January 2009 a ground-based millimeter-wave spectrometer (GBMS) was installed at Thule Air Base (76.5ºN, 68.8ºW), Greenland, for long-term winter monitoring of several stratospheric and mesospheric trace gases in the framework of the Network for the Detection of Atmospheric Composition Change. This work is aimed at characterizing the GBMS O3 vertical profiles between 35 and 80 km altitude obtained by applying the optimal estimation method to O3 pressure-broadened spectral line measurements carried out during three winters. In this altitude range, GBMS O3 retrievals are highly sensitive to variations of the atmospheric state, and their accuracy is estimated to be the larger of 11% or 0.2 ppmv. Comparisons of GBMS O3 profiles with colocated satellite-based measurements from Aura Microwave Limb Sounder (MLS) and Thermosphere Ionosphere Mesosphere Energetics and Dynamics Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) show a good agreement below 65 km altitude once the known 10%–20% high bias of SABER O3 profiles is considered, with the GBMS displaying an averaged low bias of 9% and 17% with respect to MLS and SABER. In the nighttime mesosphere, the GBMS detects the ozone tertiary maximum within 0.1 ppmv (6%) on average with respect to the convolved MLS, SABER, and global 3-D ROSE model profiles but shifts its position to lower altitudes by 4–5 km compared to the height obtained by the other three data sets. In the 50–80 km altitude range, estimates of mesospheric O3 diurnal variation obtained from the GBMS and the convolved satellite measurements agree well within the ±1 standard deviation (~ 0.6 ppmv) of the GBMS mean profile.554 75 - PublicationRestrictedTortonian-Pleistocenic oceanic features in the Southern Tyrrhenian Sea: magnetic inverse model of the Selli-Vavilov region(2008)
; ; ; ; ;Cocchi, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Caratori Tontini, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Carmisciano, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Marani, M.; ISMAR-CNR, Sezione di Geologia Maina, via P. Gobetti 101 Bologna; ;; We show the magnetic model of the Selli-Vavilov region. The Selli Line is known as the northwestern edge of the southern Tyrrhenian basin. The tectonic evolution of the Tyrrhenian basin is dominated by a Tortonian - Quaternary extension through the eastward movement of the Apennine subduction system. This migration has generated a diffuse stretching of the continental crust with the emplacement of new oceanic material. This latter occurred in several localized zones where the eastward retreating of the Ionian subduction system produced a strong depletion of the crust with formation of basins and correlated spreading. Nowadays the presence of oceanic crust is confirmed through direct drilling investigation but a complete mapping of the oceanic crustal distribution is still lacking. The Selli-Vavilov region shows a differentiated crustal setting where seamount structures, the oceanic basement portions and continental crust blocks are superimposed. To this aim, a 2D inversion of the magnetic data of this region was conducted to define buried structures. The magnetic susceptibility pattern was computed by solving the least squares problem of the misfit between the predicted and real data for separated wavebands. This method produced two 2D models of the high and low frequency fields of the Selli-Vavilov region. The two apparent susceptibility maps provide different information for distinct ranges of depth. The results of the inversions were also combined with seismic data of the Selli region highlighting the position of the highly-magnetized buried bodies. The results confirm a role for the Selli Line as a deep crustal boundary dividing the Sardinian passive domain from the easternmost active region where different oceanic structures are located. The Selli Line has worked as a detachment fault system which has moved eastward. Finally, the Selli-Vavilov region may be interpreted as a tectonic result due to a passive asymmetrical rift occurred between the Tortonian and Pliocene.299 35 - PublicationRestrictedA statistical analysis of low frequency geomagnetic field pulsations at two Antarctic geomagnetic observatories in the polar cap region(2013-05-02)
; ; ; ; ;Pietrolungo, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Lepidi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Cafarella, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Di Mauro, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; ; ; The aim of this study is to investigate the characteristics of low frequency ( 0.5–5 mHz) geomagnetic field fluctuations as recorded at two Antarctic stations within the polar cap: the Italian observatory Mario Zucchelli Station (TNB) and the French–Italian observatory Dome C (DMC) in order to investigate the spatial extension and propagation characteristics of the phenomena observed at very high latitude. The stations have approximately the same geographic latitude, but a very different corrected geomagnetic latitude, being DMC close to the geomagnetic pole and TNB closer to the auroral oval. Our study focused on power spectra, coherence and phase difference between low frequency fluctuations analyzing the horizontal H component measured during the entire year 2006. The fluctuation power behavior during the day can be explained according to the positions of the stations with respect to the polar cap; indeed in the dayside sector it is higher in the cusp region, while in the nightside sector it is higher close to the geomagnetic pole. Furthermore the study of coherent fluctuations, focusing on their phase difference, indicated that the propagation direction within the cap is variable during the day: in the dayside and nightside regions it is from the auroral oval toward the geomagnetic pole, while in the magnetic local morning and afternoon sectors it is from the geomagnetic pole toward the dawn–dusk meridian. Finally the analysis of two individual pulsation events, consisting of short duration wave packets, is shown; it confirms the statistical considerations on the propagation direction and allows to estimate the wave number and apparent phase velocity, whose values are of the order of 3–4 and 30–15 km/s, respectively.518 65 - PublicationRestrictedGeophysical investigations of an anthropogenic sinkhole in the Montelibretti village (Rome, central Italy)(2015-12)
; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ;; ; On May 2010, due to heavy rainfall, a sinkhole developed in correspondence of the S.P. Carolano roadway (1+200 km, Montelibretti, Roma), in the southernmost sector of the Sabina area. The collapse is located in correspondence of a “U like” shaped profile of the roadway crossing the central sector of a NNW trending valley. In order to obtain a more complete geological characterization of the sinkhole phenomenon, gravity, seismic and electrical investigations have been carried out on the base of previous detailed studies, historical sources and maps. Due to recent propagation of the sinkhole, probably related to the anthropogenic alteration of the superficial drainage network in previous times and recently triggered by heavy rains, local authorities decided to promptly fill the sinkhole with arid material, in order to preserve public safety. In this study is suggested the restoration of the natural runoff of the water flow in the area.582 14 - PublicationOpen AccessHigh-resolution cyclochronology of the lowermost Ypresian Arnakatxa section (Basque-Cantabrian basin, western Pyrenees)The early Eocene paleoclimate record provides one of the best analogues for today’s 9 global warming. In order to reconstruct the evolution of the early Eocene paleoclimate, 10 and understand how environmental feedback mechanisms acted on it, an accurate time 11 framework is necessary. In this regard, the astronomically calibrated time scale (ATS) 12 provides the highest possible resolution, but models beyond 40-50 Ma are not fully 13 resolved and actual geological data are incomplete. With the aim of filling this gap, the 14 expanded lower Ypresian Arnakatxa section studied herein offered a potentially 15 valuable orbitally paced geological record. This outcrop displays a well-defined 16 arrangement of strata in couplets and bundles. The spectral analyses of colour data 17 series showed the dominance of two main periodicities, which were related to orbital 18 forcing on sedimentation by precession (20 kyr) and short (100 kyr) eccentricity cycles. 19 Despite not being represented in the spectrograms, the influence of long (405 kyr) 20 eccentricity on sedimentation was also deduced. Moreover, the disruption of the orbital 21 signal in the upper half of the Arnakatxa section correlates with a very long (2.4 Myr) 22 eccentricity node centred at ~54.6 Ma, which could also have caused the amplification 23 of the orbital signal related to obliquity (41 kyr). Taking everything into account, the 24 cyclostratigraphic analyses carried out in Arnakatxa resulted in a precessional scale orbital chronology for the time interval between 55.805 and 54.435 Ma (duration of 26 1.37 Myr). Thus, the Arnakatxa succession could be reliably correlated with Atlantic 27 ODP records, which are the main reference for Ypresian astrochronology, at 28 precessional scale. Furthermore, the results from Arnakatxa also help to identify the 29 astronomical solutions that better match actual geological data, contributing to the 30 construction of a definitive Ypresian ATS. In this regard, the Arnakatxa results are not a 31 good fit for solutions La10a, La10d, La11 and ZB18, but match well with the previously 32 thought to be less reliable solutions La10b and La10c.
124 82 - PublicationRestrictedRenewal models of seismic recurrence applied to paleoseismological and historical observations(2012-09-05)
; ; ; ;Mosca, I.; Department of Earth and Environmental Sciences, LMU, Munich, Germany ;Console, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;D'Addezio, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; Because paleoseismology can extend the record of earthquakes back in time up to several millennia, it represents an opportunity to study how earthquakes recur through time and thus to provide innovative contributions to seismic hazard assessment. Based on a database of recurrence from paleoseismology we collected 19 sequences with 5 up to 14 dated events on a single fault. By using the age of the paleoearthquakes, with their associated uncertainty, and the historical earthquakes, we tested the null hypothesis that the observed inter-event times come from a uniform random distribution (Poisson model). We used the concept of likelihood for a speci!c sequence of events under a given occurrence model. The difference dlnL of the likelihoods estimated under two hypotheses gives an indication of which between the two hypotheses !ts better the observations. To take into account the uncertainties, we used a Monte Carlo procedure computing the average and the standard deviation of dlnL for 1000 inter-event sets by choosing the occurrence time of each event within the limits of uncertainty and estimating the probability that a value equal to or larger than an observed dlnL comes by chance from a Poisson distribution of inter-event times. These tests were carried out for the Log-normal, Gamma, Weibull, Double-exponential and Brownian Passage Time (BPT) distributions. Our results show that a renewal model, associated with a time dependent hazard, and some kind of predictability of the next large earthquake on a fault is signi!cantly better than a plain time-independent Poisson model only for four, out of the 19 sites examined in this study. The lack of regularity in the earthquake occurrence for more than 30% of the examined faults can be explained either by the large uncertainties in the estimate of paleoseismological occurrence times or by physical interaction between neighboring faults.222 27 - PublicationOpen AccessUnusual nighttime impulsive foF2 enhancement below the southern anomaly crest under geomagnetically quiet conditions(2011-12-09)
; ; ; ; ; ; ;Pezzopane, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Fagundes, P. R. ;Ciraolo, L. ;Correia, E. ;Cabrera, M. A. ;Ezquer, R. G.; ; ; ; ;An unusual nighttime impulsive electron density enhancement was observed on 6 March 2010 over a wide region of South America, below the southern crest of the equatorial anomaly, under low solar activity and quiet geomagnetic conditions. The phenomenon was observed almost simultaneously by the F2 layer critical frequency ( foF2) recorded at three ionospheric stations which are widely distributed in space, namely Cachoeira Paulista (22.4°S, 44.6°W, magnetic latitude 13.4°S), São José dos Campos (23.2°S, 45.9°W, magnetic latitude 14.1°S), Brazil, and Tucumán (26.9°S, 65.4°W, magnetic latitude 16.8°S), Argentina. Although in a more restricted region over Tucumán, the phenomenon was also observed by the total electron content (TEC) maps computed by usingmeasurements from 12 GPS receivers. The investigated phenomenon is very particular because besides being of brief duration, it is characterized by a pronounced compression of the ionosphere. This compression was clearly visible both by the virtual height of the base of the F region (h′F) recorded at the aforementioned ionospheric stations, and by both the vertical electron density profiles and the slab thickness computed over Tucumán. Consequently, neither an enhanced fountain effect nor plasma diffusion from the plasmasphere can be considered as the single cause of this unusual event. A thorough analysis of isoheight and isofrequency ionosonde plots suggest that traveling ionospheric disturbances (TIDs) caused by gravity wave (GW) propagation could have likely played a significant role in causing the phenomenon.371 349