bluuebunny/crossref_metadata_2025 huggingface dataset:
Seismic hazard maps of Italy
Authors: D. Slejko  , L. Peruzza  , A. Rebez
Published: June 2021

The Italian "Gruppo Nazionale per la Difesa dai Terremoti" has conducted a project in recent years for assessing seismic hazard in the national territory to be used as a basis for the revision of the current seismic zonation. In this project the data on the major earthquakes were reassessed and a new earthquake data file prepared. Definition of a seismotectonic model for the whole territory, based on a structural-kinematic analysis of Italy and the surrounding regions, led to the definition of 80 seismogenic zones, for which the geological and seismic characteristics were determined. Horizontal PGA and macroseismic intensity were used as seismicity parameters in the application of the Cornell probabilistic approach. The main aspects of the seismic hazard assessment are here described and the results obtained are presented and discussed. The maps prepared show the various aspects of seismic hazard which need to be considered for a global view of the problem. In particular, those with a 475-year return period, in agreement with the specifications of the new seismic Eurocode EC8, can be considered basic products for a revision of the present national seismic zonation.
The marine digital terrain model of the Panarea caldera (Aeolian Islands, Southern Italy)
Authors: M. Anzidei
Published: June 2021

A Marine Digital Elevation Model (MDEM) of the still active volcanic area of Panarea caldera is presented in this paper. A fast and accurate survey was performed by means of the Differential Global Positioning System (DGPS) geodetic technique coupled with an echo-sounding gear and a real time navigation software. The instrumentation was installed on board of a low draught boat in order to collect data starting from the bathymeter of one meter. Planar positions and depths were obtained with average accuracies of 30 cm and 10 cm respectively providing a 3D map of the seafloor useful for geomorphological, geophysical and volcanic hazard applications.
One dimensional motion of a viscous fluid
Authors: C. DE SIMONE  , R. PURUNI  , E. SALUSTI
Published: June 2021

The effect of the friction has been studied on the one dimensional motion of a viscous fluid. This friction is usually schematized in various semiempirical formulae. In t-liis work the different scliematizations of the friction were not studied separately but it was shown that a solution exists for the fluid motion. The results give information on the damping of the fluid motion in the case of the seiches.
ON the linear theory of viscoelastic porous media
Authors: E. BOSCHI
Published: June 2021

This paper is concerned with a reciprocity theorem and a variational theorem in the linear theory of viscoelastic porous media in t h e quasi-static case.
Evaluation of automatic ionogram scaling for use in real-time ionospheric density profile specification: Dourbes DGS-256/ARTIST-4 performance
Authors: Stanimir M. Stankov  , Jean-Claude Jodogne  , Ivan Kutiev  , Koen Stegen  , René Warnant
Published: June 2021

Statistical evaluation of the Dourbes (4.6˚E, 50.1˚N) digisonde automatic scaling of the more frequently used ionospheric parameters (foF2, foF1, foE, h’F2, h’F, h’E, and M3000F2) was performed using automatically and manually scaled data from the time period of 2002 to 2008. Automatic scaling was provided in 92% to 94% of cases for most characteristics, except for foF1 (81%). In terms of the automatic scaling accuracy, the magnitude of the residual error for foF2 and M3000F2 (automatically minus manually scaled values) varied according to local time, season, and solar activity. Although geomagnetic storms appear to affect the automatic scaling, the overall results for the influence of geomagnetic activity were inconclusive. Based on this analysis, error bounds were determined (95% probability) for each characteristic: foF2 (–0.75,+0.85), foF1(–0.25,+0.35), foE(–0.35,+0.40), h’F2(–68,+67), h’F(–38,+32), h’E(–26,+2), and M3000F2(–0.55,+0.45).
Premières applications de la magnéto-tellurique à la prospection pétrolière, géologique ou minière de diverses régions métropolitaines
Authors: A. DUPIS
Published: June 2021

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Secular variation on the territory of the Czech Republic and reduction of the magnetic survey to the epoch 2010.5
Authors: Pavel Hejda  , Josef Horáček  , Tomáš Bayer
Published: June 2021

A recent stage of the magnetic surveying activities in the Czech Republic was started in the fifties by setting up a basic network of the first order. It consists of 199 points. Complete measurements of three components, D, H, and Z, were carried out in 1976-78 and 1994-96. Since 1970 six selected points have been revisited approximately every two years. Five of them are situated close to the Czech boundaries, the last one inland. The repeat station network was complemented by another inland station in 2003. The repeat station measurements, together with the data from neighboring observatories, were now used to reduce the data from the last magnetic survey to the epoch 2010.5 and new magnetic charts were drawn. The accuracy of the results and their comparison with IGRF model is also discussed.
Re-evaluation of the macroseismic effects produced by the March 4, 1977, strong Vrancea earthquake in Romanian territory
Authors: Aurelian Pantea  , Angela Petruta Constantin
Published: June 2021

In this paper, the macroseismic effects of the subcrustal earthquake in Vrancea (Romania) that occurred on March 4, 1977, have been re-evaluated. This was the second strongest seismic event that occurred in this area during the twentieth century, following the event that happened on November 10, 1940. It is thus of importance for our understanding of the seismicity of the Vrancea zone. The earthquake was felt over a large area, which included the territories of the neighboring states, and it produced major damage. Due to its effects, macroseismic studies were developed by Romanian researchers soon after its occurrence, with foreign scientists also involved, such as Medvedev, the founder of the Medvedev-Sponheuer-Karnik (MSK) seismic intensity scale. The original macroseismic questionnaires were re-examined, to take into account the recommendations for intensity assessments according to the MSK-64 macroseismic scale used in Romania. After the re-evaluation of the macroseismic field of this earthquake, the intensity dataset was obtained for 1,620 sites in Romanian territory. The re-evaluation was necessary as it has confirmed that the previous macroseismic map was underestimated. On this new map, only the intensity data points are plotted, without tracing the isoseismals.
Preface
Authors: Pier Francesco Biagi  , Michael E. Contadakis  , Masashi Hayakawa  , Tommaso Maggipinto
Published: June 2021

Over the last several years, a lot of evidence has indicated that the earthquake generation process is a critical phenomenon, which culminates in a large event that corresponds to a critical point. A fundamental prediction of this hypothesis is that before the event reaches this critical point, a regional system of faults goes through a period of accelerating seismicity and seismic energy release, which forms the signature of the approach to the critical state. By the end of this stage, the critical point has been attained, and the stress exerted by friction on the shear zone, as well as the strain caused by an avalanche of fusing cracks, lead to irreversible instability and rupture. As a consequence of the processes prior to an event, changes in the physical/chemical state of the earth precede earthquakes. These variations can be called the ground precursors. There are a variety of such precursors, that are evident in their genesis, such as ground uplift and tilt, gas emissions, underground water-level fluctuations, changes in groundwater chemistry, and changes in electrical resistivity of the rock. [...]
Nuovi criteri per la prospezione sismica a rifrazione
Authors: C. CONTINI  , C. MAINO  , M. RANUCCI
Published: June 2021

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Earthquake activity in Finland and the Russian North in December 1758: rare reports and their interpretation
Authors: Ruben E. Tatevossian  , Tatiana N. Tatevossian  , Päivi Mäntyniemi
Published: June 2021

This investigation focuses on two historical earthquakes that occurred in the border region between Finland and Russian North in December 1758. They were close together in time and their magnitudes are among the largest observed in the region. We thoroughly searched for contemporary Russian and Scandinavian documentation on earthquake activity in several libraries in Moscow, Helsinki, Stockholm and Copenhagen. We found two primary reports, one from the Russian North and the other from Finland. The context and content of the reports indicate that they are independent and related to the dates of December 17 and December 31, 1758. The first occurrence was reportedly observed in Kandalaksha, Knyazhnaya Guba, Kovda, Chernaya reka and krest Vzista, and the second in Inari, Utsjoki, and Karasjok. We compiled macroseismic maps for both earthquakes and sets of possible parametric solutions that fit the sparse information available. We identified two types of uncertainty in epicenter and magnitude determination: one that stems from the ambiguity of intensity assessment at localities and the other from the spatial distribution of the data points. If no single solution is the best, we propose that all possible solutions be included in earthquake catalogs.
SULLA SUPERFICIE DI DISCONTINUITÀ' ALLA PROFONDITÀ' DI 950 K M CIRCA
Authors: P. Caloi  , F. Peronaci
Published: June 2021

Si portano nuovi elementi in favore dell'esistenza di una superficiedi discontinuità nel mantello terrestre, capace di riflettere unapiccola percentuale dell'energia sismica incidente. Detta superficiedovrebbe trovarsi ad una profondità di 950 km circa.
LA STRUTTURA DELL'ATLANTICO
Authors: j. p. ROTHÉ
Published: June 2021

L'autore rammenta la ipotesi di lavoro da lui formulata nel 1947: l'OceanoAtlantico e diviso in due domini, una zona occidentale a carattere sintatico e unaparte orientale a struttura continentale a est della cresta mediana.L'autore considera la distribuzione degli ipocentri sismici, la forma delle coste,il prolungamento delle unità morfologiche africane, nel mare e il valore assai elevatodella velocità delle onde sismiche superficiali, propaganlesi sotto la parte occidentaledell'Atlantico. Discute lo studio di P. Caloi e collaboratori e porta nuoviargomenti a favore della sua ipotesi: dragaggio di una tacliilite (Termier) di trilobiti(Furon 1 di calcari dell'era terziaria (Ewing e Tolsioy) nella parte orientaledell'Atlantico ; teoria delle catene liminari (Glangeaud) ; risultati delle prospezionisismiche per rifrazione ottenuti ad ovest della Scozia ( H i l l ) e nelle vicinanze delleBermude (Ewing).
LE SESSE DEL LAGO DI BOLSENA
Authors: D. DI FILIPPO
Published: June 2021

Si pungono a confronto i risultati teorici degli elementi delletre prime sesse del lago di Bolsena, calcolati con i metodi di Hidakae di Defant, con quelli delle registrazioni ottenute contemporaneamentea Marta e a Bolsena da L. Palazzo il 20 luglio 1903. Vieneconstatata la perfetta concordanza tra gli uni e gli altri a convalidadella bontà dei procedimenti teorici.
DISTRIBUZIONE STATISTICA DELLE PARTICELLE α RACCOLTE SU UNA LASTRA FOTOGRAFICA IN FUNZIONE DELLA PROIEZIONE DEL PERCORSO NELL'EMULSIONE
Authors: G. IMBÒ  , L. CASERTANO
Published: June 2021

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Decoupling of ground level pressures observed in Italian volcanoes: are they driven by space weather geo-effectiveness?
Authors: Paolo Madonia  , Paolo Romano  , Salvatore Inguaggiato
Published: June 2021

Investigations on correlation drops between near-ground atmospheric pressures measured at sea level and at higher altitudes on Italian volcanoes have been carried out. We looked for perturbations of the atmospheric pressure field driven by volcanic activity, but not excluding possible external triggers for the observed anomalies. Decorrelations between atmospheric pressures measured at Stromboli Island in stations located at different altitudes (years 2002-10) have been analysed and compared with data from other volcanic (Vesuvius) and non volcanic (Mt. Soro) orographic structures. We investigated as their possible triggers volcanic, meteorological and space weather parameters, with particular attention to Total Solar Irradiance (TSI), Kp index and Forbush decreases. Pressure decorrelations seems to be driven by astronomic cycles, with maxima in summer and minima in winter. A further contribution was found, seemingly assignable to TSI anomalies, with correlation minima occurring 12 hours after these but only during phases of high Sun activity. Moreover, during the same phases a main periodicity of about 27 days in pressure decorrelations was revealed by FFT analysis. This period is the same of the Sun Carrington rotation, expressing the periodic reappearance of sunspot groups on Sun’s surface. The strong similarity between recurrences of sunspot number and atmospheric pressure anomalies further supports the role of the former as a possible trigger for the latter.
Looking for missing earthquake traces in the Ferrara-Modena plain: an update on historical seismicity
Authors: Viviana Castelli  , Filippo Bernardini  , Romano Camassi  , Carlos H. Caracciolo  , Emanuela Ercolani  , Luca Postpischl
Published: June 2021

According to the latest issue of the Italian seismic catalogue [Rovida et al. 2011], the area most affected by the May-June 2012 Emilia sequence [for an overview, vide Galli et al. 2012; Tertulliani et al. 2012, this volume] has a centuries-old seismic history of comparatively low magnitude events. These have been on a par with those that have occurred in the nearby Reggiano-Parmense area (where M 4.5 to M 5.5 earthquakes were comparatively frequent in the last century), although less significant than those on record in the portion of the northern Apennines that forms the southern boundary of the Pia-nura Padana (Figure 1), and a lot lower than in the most seismically active zones of the Italian peninsula. Magnitude ca. 5.5 earthquakes are known to have occurred near Ferrara (in 1346, 1561) and in the areas of Finale Emilia-Bondeno (1574, 1908, 1986), Mantua (1901) and Cento (1922). However, this picture might be incomplete, as suggested by the recent discovery of a previously unknown earthquake that occurred in 1639, whose maximum intensity was assessed as 7-8 Mercalli–Cancani–Sieberg (MCS) in Finale Emilia by Camassi et al. [2011a]. [...]
Source complexity of the May 20, 2012, Mw 5.9, Ferrara (Italy) event
Authors: Davide Piccinini  , Nicola Alessandro Pino  , Gilberto Saccorotti
Published: June 2021

A Mw 3.9 foreshock on May 19, 2012, at 23:13 UTC, was followed at 02:03 on May 20, 2012, by a Mw 5.9 earthquake that hit a densely populated area in the Po Plain, west of the city of Ferrara, Italy (Figure 1). Over the subsequent 13 days, six Mw >5 events occurred; of these, the most energetic was a Mw 5.8 earthquake on May 29, 2012, 12 km WSW of the main shock. The tragic balance of this sequence was 17 casualties, hundreds of injured, and severe damage to the historical and cultural heritage of the area. From a seismological point of view, the 2012 earthquake was not an outstanding event in its regional context. The same area was hit in 1996 by a Mw 5.4 earthquake [Selvaggi et al. 2001], and previously in 1986 and in 1967 (DBMI11) [Locati et al. 2011]. The most destructive historical event was the 1570, Imax 8 event, which struck the town of Ferrara [Guidoboni et al. 2007, Rovida et al. 2011]. The 2012 seismic sequence lasted for several weeks and probably developed on a well-known buried thrust fault [Basili et al. 2008, Toscani et al. 2009, DISS Working Group 2010], at depths between 2 km and 10-12 km. […]
INGV strong-motion data web-portal: a focus on the Emilia seismic sequence of May-June 2012
Authors: Marco Massa  , Sara Lovati  , Dario Sudati  , Gianlorenzo Franceschina  , Emiliano Russo  , Rodolfo Puglia  , Gabriele Ameri  , Lucia Luzi  , Francesca Pacor  , Paolo Augliera
Published: June 2021

[…] Recently, an INGV working group developed the first version of a web portal with the aim of archiving, processing and distributing accelerometric data recorded by permanent and temporary INGV stations. This web portal (www.mi.ingv.it/ISMD/) is composed of two main modules: the former is known as the INGV Strong Motion Data (ISMD, www.mi.ingv.it/ISMD/ismd.html/) and has as its main scope the analyse and distribution in quasi-real time (a few hours after event occurrence) of the uncorrected accelerometric data, and the related metadata obtained after an automatic processing procedure. This latter, known as the Dynamic Archive (DYNA, http://dyna.mi.ingv.it/DYNA-archive/) is a dynamic database where manually post-processed accelerometric waveforms are provided, together with their metadata. Both of these archives are designed and structured in such a way that their compilations and updating will be almost completely automatic. At the end of May 2012, a first prototype of the ISMD module was published, providing the uncorrected strong-motion data recorded by the INGV stations for the main events of the Emilia seismic sequence. […]
GPS observations of coseismic deformation following the May 20 and 29, 2012, Emilia seismic events (northern Italy): data, analysis and preliminary models
Authors: Enrico Serpelloni  , Letizia Anderlini  , Antonio Avallone  , Valentina Cannelli  , Adriano Cavaliere  , Daniele Cheloni  , Ciriaco D'Ambrosio  , Elisabetta D'Anastasio  , Alessandra Esposito  , Grazia Pietrantonio  , Anna Rita Pisani  , Marco Anzidei  , Gianpaolo Cecere  , Nicola D'Agostino  , Sergio Del Mese  , Roberto Devoti  , Alessandro Galvani  , Angelo Massucci  , Daniele Melini  , Federica Riguzzi  , Giulio Selvaggi  , Vincenzo Sepe
Published: June 2021

In May-July 2012, a seismic sequence struck a broad area of the Po Plain Region in northern Italy. The sequence included two Ml >5.5 mainshocks. The first one (Ml 5.9) occurred near the city of Finale Emilia (ca. 30 km west of Ferrara) on May 20 at 02:03:53 (UTC), and the second (Ml 5.8) occurred on May 29 at 7:00:03 (UTC), about 12 km southwest of the May 20 mainshock (Figure 1), near the city of Mirandola. The seismic sequence involved an area that extended in an E-W direction for more than 50 km, and included seven Ml ≥5.0 events and more than 2,300 Ml >1.5 events (http://iside.rm.ingv.it). The focal mechanisms of the main events [Pondrelli et al. 2012, Scognamiglio et al. 2012, this volume] consistently showed compressional kinematics with E-W oriented reverse nodal planes. This sector of the Po Plain is known as a region characterized by slow deformation rates due to the northwards motion of the northern Apennines fold-and-thrust belt, which is buried beneath the sedimentary cover of the Po Plain [Picotti and Pazzaglia 2008, Toscani et al. 2009]. Early global positioning system (GPS) measurements [Serpelloni et al. 2006] and the most recent updates [Devoti et al. 2011, Bennett et al. 2012] recognized that less than 2 mm/yr of SW-NE shortening are accommodated across this sector of the Po Plain, in agreement with other present-day stress indicators [Montone et al. 2012] and known active faults [Basili et al. 2008]. In the present study, we describe the GPS data used to study the coseismic deformation related to the May 20 and 29 mainshocks, and provide preliminary models of the two seismic sources, as inverted from consensus GPS coseismic deformation fields. […]
Morphotectonics of the Padul-Nigüelas Fault Zone, southern Spain
Authors: Jochen Hürtgen  , Andreas Rudersdorf  , Christoph Grützner  , Klaus Reicherter
Published: June 2021

The Padul-Nigüelas Fault Zone (PNFZ) is situated at the south-western mountain front of the Sierra Nevada (southern Spain) in the Internal Zone of the Betic Cordilleras and belongs to a NW-SE trending system of normal faults dipping SW. The PNFZ constitutes a major tectonic and lithological boundary in the Betics, and separates the metamorphic units of the Alpujárride Complex from Upper Tertiary to Quaternary deposits. Due to recent seismicity and several morphological and geological indicators, such as preserved fault scarps, triangular facets, deeply incised valleys and faults in the colluvial wedges, the PNFZ is suspected to be a tectonically active feature of the south-eastern Granada Basin. We performed morphotectonic GIS analyses based on digital elevation models (DEM, cell size: 10 m) to obtain tectonic activity classes for each outcropping segment of the PNFZ. We have determined the following geomorphic indices: mountain front sinuosity, stream-length gradient index, concavity index and valley floor width to height ratio. The results show a differentiation in the states of activity along the fault zone strike. The western and eastern segments of the PNFZ indicate a higher tectonic activity compared to the center of the fault zone. We discuss and critically examine the comparability and reproducibility of geomorphic analyses, concluding that careful interpretation is necessary, if no ground-truthing can be performed.
Neotectonics of Graciosa island (Azores): a contribution to seismic hazard assessment of a volcanic area in a complex geodynamic setting
Authors: Ana Hipólito  , José Madeira  , Rita Carmo  , João Luís Gaspar
Published: June 2021

Graciosa is a mid-Pleistocene to Holocene volcanic island that lies in a complex plate boundary between the North American, Eurasian, and Nubian plates. Large fault scarps displace the oldest (Middle Pleistocene) volcanic units, but in the younger areas recent volcanism (Holocene to Upper Pleistocene) conceals the surface expression of faulting, limiting neotectonic observations. The large displacement accumulated by the older volcanic units when compared with the younger formations suggests a variability of deformation rates and the possibility of alternating periods of higher and lower tectonic deformation rates; this would increase the recurrence interval of surface rupturing earthquakes. Nevertheless, in historical times a few destructive earthquakes affected the island attesting for its seismic hazard. Regarding the structural data, two main fault systems, incompatible with a single stress field, were identified at Graciosa Island. Thus, it is proposed that the region is affected by two alternating stress fields. The stress field #1 corresponds to the regional stress regime proposed by several authors for the interplate shear zone that constitutes the Azorean segment of the Eurasia-Nubia plate boundary. It is suggested that the stress field #2 will act when the area under the influence of the regional stress field #1 narrows as a result of variations in the differential spreading rates north and south of Azores. The islands closer to the edge of the sheared region will temporarily come under the influence of a different (external) stress field (stress field #2). Such data support the concept that, in the Azores, the Eurasia-Nubia boundary corresponds to a complex and wide deformation zone, variable in time.
Introduction
Authors: Stefano Gresta
Published: June 2021

The Emilia seismic sequence that struck northern Italy on May-June 2012 had a relevant social, cultural, emotional and economical impact. There were 17 victims, and it caused severe damage in many localities, especially to the historical centers and factories. From the scientific point of view, the sequence represented an important case study and the whole geophysical community focused their attention on it. [...]
GPS scintillations and total electron content climatology in the southern low, middle and high latitude regions
Authors: Luca Spogli  , Lucilla Alfonsi  , Pierre J. Cilliers  , Emília Correia  , Giorgiana De Franceschi  , Cathryn N. Mitchell  , Vincenzo Romano  , Joe Kinrade  , Miguel Angel Cabrera
Published: June 2021

In recent years, several groups have installed high-frequency sampling receivers in the southern middle and high latitude regions, to monitor ionospheric scintillations and the total electron content (TEC) changes. Taking advantage of the archive of continuous and systematic observations of the ionosphere on L-band by means of signals from the Global Positioning System (GPS), we present the first attempt at ionospheric scintillation and TEC mapping from Latin America to Antarctica. The climatology of the area considered is derived through Ground-Based Scintillation Climatology, a method that can identify ionospheric sectors in which scintillations are more likely to occur. This study also introduces the novel ionospheric scintillation 'hot-spot' analysis. This analysis first identifies the crucial areas of the ionosphere in terms of enhanced probability of scintillation occurrence, and then it studies the seasonal variation of the main scintillation and TEC-related parameters. The results produced by this sophisticated analysis give significant indications of the spatial/ temporal recurrences of plasma irregularities, which contributes to the extending of current knowledge of the mechanisms that cause scintillations, and consequently to the development of efficient tools to forecast space-weather-related ionospheric events.
Electromagnetic background noise at L’Aquila Geomagnetic Observatory
Authors: Lucia Santarelli  , Paolo Palangio  , Marcello De Lauretis
Published: June 2021

 

In this paper we analyze the electromagnetic background noise at L’Aquila Geomagnetic Observatory during 2006 and 2007 in the frequency band 1-100 mHz. In this band a pronounced daily variation is observed both in the natural signals as well as in the artificial ones, giving rise to the problem of separating different contributions of very similar morphology. We analyzed periods when the local K index was approximately zero, in correspondence with minimum of the magnetospheric and ionospheric activity. We found that in our area the main source of artificial noise is constituted by the DC electrified railways.
ACE-FTS version 3.0 data set: validation and data processing update
Authors: Claire Waymark  , Kaley Walker  , Chris D. Boone  , Peter F. Bernath
Published: June 2021

On 12 August 2003, the Canadian-led Atmospheric Chemistry Experiment (ACE) was launched into a 74° inclination orbit at 650 km with the mission objective to measure atmospheric composition using infrared and UV-visible spectroscopy (Bernath et al. 2005). The ACE mission consists of two main instruments, ACE-FTS and MAESTRO (McElroy et al. 2007), which are being used to investigate the chemistry and dynamics of the Earth’s atmosphere.  Here, we focus on the high resolution (0.02 cm-1) infrared Fourier Transform Spectrometer, ACE-FTS, that measures in the 750-4400 cm-1 (2.2 to 13.3 µm) spectral region.  This instrument has been making regular solar occultation observations for more than nine years.  The current ACE-FTS data version (version 3.0) provides profiles of temperature and volume mixing ratios (VMRs) of more than 30 atmospheric trace gas species, as well as 20 subsidiary isotopologues of the most abundant trace atmospheric constituents over a latitude range of ~85°N to ~85°S.  This letter describes the current data version and recent validation comparisons and provides a description of our planned updates for the ACE-FTS data set. [...]
Description of ionospheric disturbances observed by Vertical Ionospheric Sounding at 3 MHz
Authors: James Arokiasami Baskaradas  , Silvio Bianchi  , Marco Pietrella  , Michael Pezzopane  , Umberto Sciacca  , Enrico Zuccheretti
Published: June 2021

High Frequency radio waves reflected by the ionosphere can provide a relevant amount of information within the composite received signal. The ionosphere is indeed a frequency dispersive, bi-refractive, absorbing medium, in which multipath propagation occurs due to disturbance on a varied time-spatial scale. On the time-spatial level of Small Scale Disturbances (SSD) the ionosphere dynamics, detectable by Vertical Ionospheric Sounding (VIS), is mainly dependent on wrinkled layers acting as multi-reflectors. The present paper discusses different aspects of the effects of multipath fading suffered by the wave along the propagation path and potentially associated with SSD. To achieve these objectives, a VIS campaign at a fixed frequency of 3.0 MHz was conducted at the ionospheric observatory in Rome (Latitude 41.8 N; Longitude 12.5 E), by collecting a series of measurements of the power variations in received echo signals recorded between two consecutive ionograms whose sounding repetition rate was set to 15 min. The obtained results show that: 1) the fading suffered by the wave follows either a Rayleigh trend or a Nakagami-Rice trend, or a mix of them, the mixed case being the most frequent (about 65 % of the analysed cases); 2) the predominant periodicities characterizing the power variation are less than 25 s; such values are compatible with the small scale ionospheric disturbances; 3) for all the 24 hours of the day the ionospheric reflector is pretty stable and for time intervals of 10-30 s the periods of stability occur with a percentage of occurrence ranging between 55% and 95 %; for time intervals of 190- 210 s the periods of stability occur instead with a percentage of occurrence ranging between 5% and 54 %.
Integration of historical, archaeoseismic and paleoseismological data for the reconstruction of the early seismic history in Messina Strait (south Italy): the 1st and 4th centuries AD earthquakes
Authors: Maria Serafina Barbano  , Viviana Castelli  , Daniela Pantosti  , Claudia Pirrotta
Published: June 2021

Historical accounts, archaeoseismic and paleoseismological evidence allowed us to reappraise two earthquakes affecting northeastern Sicily and southern Calabria in the 1st (probably between 14 and 37) and 4th (likely between 361 and 363) centuries AD, to obtain a better reconstruction of their effects and to reconsider their sources.The 1st century event damaged the area from Oppido (Calabria) to Tindari (Sicily), roughly that of the February 6, 1783 Calabria earthquake. The similitude of these earthquakes is further stressed by the fact that they generated tsunamis, as recorded by historical data and by the tsunami deposits found at Capo Peloro, the oldest dated 0-125 AD, the youngest linked to the 1783 event. These earthquakes could be related to the same Calabria seismic source: the Scilla fault. Northeastern Sicily and southern Calabria were also damaged by one or more earthquakes in the 4th century AD and several towns were rebuilt/restored at that time. The hit area roughly coincides with that of the Messina 1908 earthquake suggesting similar seismic sources for the events. However, because close in time, historical descriptions of the 4th century Sicilian earthquake were mixed with those of the 365 Crete earthquake that generated a basin-wide tsunami most likely reaching also the Sicilian coasts. Reevaluating location, size, damage area and tsunamigenic potential of these two earthquakes of the 1st and 4th centuries AD is relevant for reassessing the seismogenic and tsunamigenic potential of the faults around the Messina Strait and the seismic hazard of the affected areas.
The Euro-Mediterranean Tsunami Catalogue
Authors: Alessandra Maramai  , Beatriz Brizuela  , Laura Graziani
Published: June 2021

A unified catalogue containing 290 tsunamis generated in the European and Mediterranean seas since 6150 B.C. to current days is presented. It is the result of a systematic and detailed review of all the regional catalogues available in literature covering the study area, each of them having their own format and level of accuracy. The realization of a single catalogue covering a so wide area and involving several countries was a complex task that posed a series of challenges, being the standardization and the quality of the data the most demanding. A “reliability” value was used to rate equally the quality of the data for each event and this parameter was assigned based on the trustworthiness of the information related to the generating cause, the tsunami description accuracy and also on the availability of coeval bibliographical sources. Following these criteria we included in the catalogue events whose reliability ranges from 0 (“very improbable tsunami”) to 4 (“definite tsunami”). About 900 documentary sources, including historical documents, books, scientific reports, newspapers and previous catalogues, support the tsunami data and descriptions gathered in this catalogue. As a result, in the present paper a list of the 290 tsunamis with their main parameters is reported. The online version of the catalogue, available at http://roma2.rm.ingv.it/en/facilities/data_bases/52/catalogue_of_the_euro-mediterranean_tsunamis, provides additional information such as detailed descriptions, pictures, etc. and the complete list of bibliographical sources. Most of the included events have a high reliability value (3= “probable” and 4= “definite”) which makes the Euro-Mediterranean Tsunami Catalogue an essential tool for the implementation of tsunami hazard and risk assessment.
The first Long Period earthquake detected in the background seismicity at Mt. Vesuvius
Authors: Paola Cusano  , Simona Petrosino  , Francesca Bianco  , Edoardo Del Pezzo
Published: June 2021

The typical earthquakes occurring at Mt. Vesuvius are Volcano-Tectonic. On July 20, 2003, an unusual earthquake with low and narrow frequency content was detected. The seismograms presented an emergent onset and a nearly monochromatic spectrum at all stations of the Osservatorio Vesuviano (Istituto Nazionale di Geofisica e Vulcanologia) seismic network. The event was located at about 4 km b.s.l. close to the crater axis and an equivalent duration magnitude of 0.6 was estimated. The nature of this event was investigated by comparing its features with those of two typical Volcano-Tectonic earthquakes occurred inside the same source volume. We compared the spectral content calculating the spectrograms and the coda patterns using the Hilbert Transform. A Seismic Moment Tensor inversion was performed on the low frequency earthquake. The focal mechanisms for the two Volcano-Tectonic earthquakes were estimated with a classical technique and resulted compatible with the stress field acting on the volcano. Taking into account the clear differences with the typical Volcano-Tectonic events as well as the peculiarities retrieved from our analyses (monochromatic, low frequency spectral content, and sustained coda) and also some geochemical observations, we classify the unusual low frequency seismic event detected at Mt. Vesuvius as Long Period earthquake and propose that its origin could be linked to a pressure drop in the deep hydrothermal system.
Neural analysis of seismic data: applications to the monitoring of Mt. Vesuvius
Authors: Antonietta M. Esposito  , Luca D’Auria  , Flora Giudicepietro  , Teresa Caputo  , Marcello Martini
Published: June 2021

The computing techniques currently available for the seismic monitoring allow advanced analysis. However, the correct event classification remains a critical aspect for the reliability of real time automatic analysis. Among the existing methods, neural networks may be considered efficient tools for detection and discrimination, and may be integrated into intelligent systems for the automatic classification of seismic events. In this work we apply an unsupervised technique for analysis and classification of seismic signals recorded in the Mt. Vesuvius area in order to improve the automatic event detection. The examined dataset contains about 1500 records divided into four typologies of events: earthquakes, landslides, artificial explosions, and “other” (any other signals not included in the previous classes). First, the Linear Predictive Coding (LPC) and a waveform parametrization have been applied to achieve a significant and compact data encoding. Then, the clustering is obtained using a Self-Organizing Map (SOM) neural network which does not require an a-priori classification of the seismic signals, groups those with similar structures, providing a simple framework for understanding the relationships between them. The resulting SOM map is separated into different areas, each one containing the events of a defined type. This means that the SOM discriminates well the four classes of seismic signals. Moreover, the system will classify a new input pattern depending on its position on the SOM map. The proposed approach can be an efficient instrument for the real time automatic analysis of seismic data, especially in the case of possible volcanic unrest.
On the point-source approximation of earthquake dynamics
Authors: Andrea Bizzarri
Published: June 2021

The focus on the present study is on the point-source approximation of a seismic source. First, we compare the synthetic motions on the free surface resulting from different analytical evolutions of the seismic source (the Gabor signal (G), the Bouchon ramp (B), the Cotton and Campillo ramp (CC), the Yoffe function (Y) and the Liu and Archuleta function (LA)). Our numerical experiments indicate that the CC and the Y functions produce synthetics with larger oscillations and correspondingly they have a higher frequency content. Moreover, the CC and the Y functions tend to produce higher peaks in the ground velocity (roughly of a factor of two). We have also found that the falloff at high frequencies is quite different: it roughly follows ω−2 in the case of G and LA functions, it decays more faster than ω−2 for the B function, while it is slow than ω−1 for both the CC and the Y solutions. Then we perform a comparison of seismic waves resulting from 3-D extended ruptures (both supershear and subshear) obeying to different governing laws against those from a single point-source having the same features. It is shown that the point-source models tend to overestimate the ground motions and that they completely miss the Mach fronts emerging from the supershear transition process. When we compare the extended fault solutions against a multiple point-sources model the agreement becomes more significant, although relevant discrepancies still persist. Our results confirm that, and more importantly quantify how, the point-source approximation is unable to adequately describe the radiation emitted during a real world earthquake, even in the most idealized case of planar fault with homogeneous properties and embedded in a homogeneous, perfectly elastic medium.
The October 20, 2006 Manyas (ML=5.2) and October 24, 2006 Gemlik (ML=5.2) earthquakes in the Marmara region (NW Turkey): ground motion characteristics
Authors: Esref Yalcinkaya
Published: June 2021

In this study, we analyze the ground motion characteristics of October 20, 2006 Manyas (ML=5.2) and October 24, 2006 Gemlik (ML=5.2) earthquakes. Both earthquakes occurred on the southern branch of the North Anatolian Fault Zone in Marmara region, which has a lower seismic hazard relative to the northern branch. The two events are the largest earthquakes on the southern branch recorded by a modern and vast seismological network; therefore their records are valuable to evaluate seismic risk of the region and the understanding of physics of wave propagation. The analysis show that the attenuation of PGAs is very similar for two earthquakes, but they are not represented by the empirical relation obtained for earthquakes occurred on the northern branch. The waveforms of the Gemlik earthquake recorded by BYTNet array indicate an EW rupture orientation with right-lateral slip which fits to the general character of the southern branch. Ground motions at the stations located within basin are strongly influenced by the presence of locally induced surface waves resulting in lengthening of significant shaking duration with respect to a nearby ridge site. Surface wave characteristics are very similar for the Manyas and Gemlik earthquakes, but variations are observed on components which may be related to 3D basin geometry. Resonance frequencies of the surface waves generated within basin are very close to the 1D site resonances at the stations obtained from H/V ratios of S waves. The resonance frequency is about 0.2 Hz within the large Bursa Plain, whereas it increases to about 0.9 Hz within the smaller Gemlik Plain.
Linear and non-linear sea-level variations in the Adriatic Sea from tide gauge records (1872-2012)
Authors: Gaia Galassi  , Giorgio Spada
Published: June 2021

We have analyzed tide gauge data from the Adriatic Sea in order to assess the secular sea-level trend, its acceleration and the existence of possible cyclic variation. Analyzing the sea-level stack of all Adriatic tide gauges, we have obtained a trend of (1.25±0.04) mm yr-1, in agreement with that observed for the last century in the Mediterranean Sea, and an acceleration that is negligibile compared to the average global values. By means of the Ensemble Empirical Mode Decomposition technique, we have evidenced an energetic oscillation with a period of ∼20 years that we relate with the recurrence of opposite phases in the Atlantic Multi–decadal Oscillation and North Atlantic Oscillation indices. We suggest that anomalously high sea-level values observed at all the Adriatic tide gauges during 2010 and 2011 can be explained by the rising phase of this 20 years cycle.
Can the Earth’s harmonic spectrum be derived directly from the stochastic inversion of global travel-time data?
Authors: Steve Della Mora  , Lapo Boschi
Published: June 2021

A set of seismic observations which all sample the same structure in the same way should have zero variance. This is naturally the case if all sources are in the same place, and the data are recorded by the same station. If sources and/or receivers are not in the same place, but close to one another, variance will generally be nonzero, but small. Variance might become large if the sampled region of the Earth contains heterogeneities whose spatial wavelength is comparable to the distances between sources and between receivers (and thus between the corresponding ray paths). The travel-time variance of a “bundle” of seismic rays thus reflects the degree of complexity of the sampled region of the medium. We apply this simple principle to real seismic databases, attempting to constrain the spherical harmonic spectrum of Earth’s structure without having to derive a tomographic model. This results in a reduction of the dimensionality of the solution space, and hence of computational costs. This approach allows to constrain the statistical properties, rather than exact geographic locations of structural features; knowing the statistics of Earth’s structure is most valuable for many fundamental geodynamic questions. We follow an earlier study by Gudmundsson et al. [1990] to find an approximate analytical relationship between averaged variance and harmonic spectrum; this allows us to determine the latter from a measurement of the former via a linear least squares inversion. Our analysis shows that the variance of ray bundles associated with large geographic extent of source/receiver bins is sensitive to low-degree spectral power, and vice-versa for small bins/high harmonic degrees. The method is accordingly ineffective at very low harmonic degrees, associated with an inherently limited number of source-receiver bins. We conduct a suite of inversions of both real and synthetic seismic data sets to evaluate the resolving power of our algorithm, and attempt to identify a range of harmonic degrees where the method is robust. Our results indicate that the resolution of the Earth’s spectrum afforded by the method presented here is inferior to that of classical tomography.
Geomagnetic polar observatories: the role of Concordia station at Dome C, Antarctica
Authors: Domenico Di Mauro  , Lili Cafarella  , Stefania Lepidi  , Manuela Pietrolungo  , Laura Alfonsi  , Aude Chambodut
Published: June 2021

A geomagnetic observatory is a permanent facility where magnetic declination and inclination are recorded in conjunction with the temporal evolution of the magnetic field components. Polar regions are scarcely covered by observational points then the contributions from observatories located there are particularly relevant. The geomagnetic observatory at Concordia station, Dome C - Antarctica is located in the inner part of the continent, its position is favorable for two key reasons, i) data are unaltered by the "coastal effect” and ii) crustal effect is negligible due to the thickness, almost 3 km, of ice coverage. Nevertheless, these latter conditions imply an unconsidered aspect which characterizes the entire station and every structure laying on the ice surface: the dome on which Concordia station resides is sliding horizontally and moving vertically with a velocity of few millimeter to centimeters per year as indicated by independent geodetic observations. This slow and continuous movement has a puzzling effect on the trend of horizontal components of the magnetic field, sampled in a time window of a decade since the establishing of the observatory in 2005. During the International Polar Year (2007-2009) the observatory was upgraded with new equipment fulfilling the requirements of the Intermagnet consortium, and becoming an observatory member in 2011. In this paper are illustrated the strategy adopted to track any possible displacement of the observatory reference points (i.e. the azimuth mark, the pillar position) and all the ordinary and extraordinary actions required for collecting high quality data.
Archaeological, archaeomagnetic and thermoluminescence investigation of a baked clay kiln excavated at Chieri, northern Italy: contribution to the rescue of our cultural heritage
Authors: Evdokia Tema  , Fulvio Fantino  , Enzo Ferrara  , Silvia Allegretti  , Alessandro Lo Giudice  , Alessandro Re  , Federico Barello  , Silvia Vella  , Luigi Cirillo  , Monica Gulmini
Published: June 2021

Combining different dating techniques is fundamental to constrain the ages of archaeological findings, mainly when direct evidences for their chronological context are not available. This paper presents the results of a combined archaeological, archaeomagnetic and thermoluminescence study of a kiln discovered during a rescue excavation at Chieri, northern Italy. The archaeological site is quite complex mainly due to the interposition of different stratigraphic levels that span from Roman times to present day. The studied kiln belongs to the post-medieval stratigraphic level but the lack of datable diagnostic objects strongly limits the possibility of its accurate dating only by means of archaeological evidences. Archaeomagnetic study was performed on 26 baked clay samples, isolating stable characteristic remanent magnetizations. The statistic comparison of the averaged direction with reference secular variation curves suggests two possible dating intervals. Independent dating from thermoluminescence study of 2 samples is consistent with the second time interval proposed by archaeomagnetism, suggesting that the kiln was abandoned at the beginning of the 17th century. The successful combination of the two independent laboratory techniques provides accurate dating of archaeological baked clays and can be used as routine for future archaeological investigations of rescue excavations.