bluuebunny/crossref_metadata_2025 huggingface dataset:
The July 17, 2011, ML 4.7, Po Plain (northern Italy) earthquake: strong-motion observations from the RAIS network
Authors: Marco Massa  , Paolo Augliera  , Gianlorenzo Franceschina  , Sara Lovati  , Maria Zupo
Published: June 2021

On July 17, 2011, at 18:30:23 UTC, a ML 4.7 earthquake occurred on the east side of the Po Plain (northern Italy), between the towns of Ferrara and Rovigo. The epicentral coordinates provided by the National Earthquake Center of the Istituto Nazionale di Geofisica e Vulcanologia (National Institute of Geophysics and Volcanology, INGV) were 45.01˚N and 11.41˚E (http://iside.rm.ingv.it/iside). The depth of the hypocenter was constrained at 8.1 km, corresponding to a buried active source that existed in the area. The source of the event was characterized by a predominant left-transverse focal mechanism, even if there was also an important reverse component. Although it did not produce relevant damage, the earthquake was clearly felt in an area of about 50 km radius around the epicenter. The maximum observed intensity was V on the Mercalli-Cancani-Sieberg (MCS) scale, with a predominant distribution of damage towards the north-west. This study provides an overview of the strong-motion waveforms of the mainshock as recorded by the RAIS (Rete Accelerometrica Italia Settentrionale) strong-motion network, in particular focusing on the recordings provided by the stations located in the central part of the basin, which were installed in correspondence with hundreds of soft sediments. The preliminary results show the relevant influence of the basin on the seismic wavefield, highlighting in particular a possible site-amplification phenomena, and also affecting the ground motion at long periods (T >1 s). The systematic underestimations provided by the empirical ground-motion predictive models calibrated for Italy in terms of acceleration response spectra up to 2.0 s support this hypothesis. The sharing of the 24 waveforms (in raw sac and ascii formats) recorded by RAIS is assured by the availability of the data at the ftp site: ftp://ftp.mi.ingv.it/download/RAIS-FR_rel01/.
 
Large ionospheric disturbances during a minor geomagnetic storm on June 23, 2000
Authors: Zheng Li  , Fengsi Wei  , Xueshang Feng  , Jianpeng Guo  , Barbara A Emery  , Xinhua Zhao
Published: June 2021

We investigate the variations in the ionosphere during a small geomagnetic storm on June 23, 2000, using the total electron content of the Jet Propulsion Laboratory global positioning system, and the ionospheric critical frequency. Large and long-lasting reductions in the daytime electron density were observed at mid-latitudes in the northern hemisphere by ionosondes. These reductions reached 30% to 40% compared to the 27-day median value. At the same time, a transformation from similar large positive storm effects to negative storm effects was observed in the northern hemisphere by the global positioning system receivers. The geomagnetic disturbance was very weak from June 23-25, 2000, as the SYM-H index was >−40 nT and ASY-H was <90 nT. Of note, during this case there were neither long-lasting southward IMF Bz nor strong positive IMF By components, where a large positive IMF By might be the main reason for ionospheric storms during minor geomagnetic disturbances [Goncharenko et al. 2006]. We confirm a 13-h enhanced energy input from the disturbed solar wind by calculation of the Borovsky, Akasofu and Newell coupling functions, the global auroral precipitation, and the Joule heating. We suggest this enhanced energy input as the main cause of these intense ionospheric storms, although the maximum of the energy input was not large. In addition, we propose that the Newell coupling function might be more suitable for reflecting the energy transfer from the disturbed solar wind to the magnetosphere under weak geomagnetic activity.
How to control a temporary DIDD based observatory in the field?
Authors: András Csontos  , Danijel Šugar  , Mario Brkić  , Péter Kovács  , László Hegymegi
Published: June 2021

One of the main challenges on the course of the repeat station surveys is to determine the spatial differences of the geomagnetic elements between the repeat stations and the reference observatory. The difficulty arises from the fact, that the directly obtained differences are affected not only by spatial but also by temporal effects of external origin. The error deriving from the external effects can be efficiently diminished by the installation of an on-site vector variometer. In this case the spatial difference can be computed for night-time period, when the external field is less varying (both spatially and temporally) than during daytime. Installation of the on-site variometer in the field requires the fulfillment of nearly the same conditions as in the observatories, i.e. the control of the reference frame, the scale factors, the offsets, and the temperature effects of the magnetometer. The principle of the fluxgate and DIDD magnetometers is quite different from each other, therefore the two devices provide different possibilities to obtain accurate result. The paper discusses some of the possible instrumental errors and offers a method based on the DIDD technology for the determination of the reference frame of a portable recording station. We analyse real records measured during the joint Hungarian-Croatian repeat station survey.
The interseismic velocity field of the central Apennines from a dense GPS network
Authors: Alessandro Galvani  , Marco Anzidei  , Roberto Devoti  , Alessandra Esposito  , Grazia Pietrantonio  , Anna Rita Pisani  , Federica Riguzzi  , Enrico Serpelloni
Published: June 2021

Since 1999, we have repeatedly surveyed the central Apennines through a dense survey-style geodetic network, the Central Apennines Geodetic Network (CAGeoNet). CAGeoNet consists of 123 benchmarks distributed over an area of ca. 180 km × 130 km, from the Tyrrhenian coast to the Adriatic coast, with an average inter-site distance of 3 km to 5 km. The network is positioned across the main seismogenic structures of the region that are capable of generating destructive earthquakes. Here, we show the horizontal GPS velocity field of both CAGeoNet and continuous GPS stations in this region, as estimated from the position–time series in the time span from 1999 to 2007. We analyzed the data using both the Bernese and GAMIT software, rigorously combining the two solutions to obtain a validated result. Then, we analyzed the strain-rate field, which shows a region of extension along the axis of the Apennine chain, with values from 2 × 10–9 yr–1 to 66·× 10–9 yr–1, and a relative minimum of ca. 20 × 10–9 yr–1 located in the L'Aquila basin area. Our velocity field represents an improved estimation of the ongoing elastic interseismic deformation of the central Apennines, and in particular relating to the area of the L'Aquila earthquake of April 6, 2009.
A new formulation of Stokes’ approach in determining the global gravimetric geoid
Authors: Wen-Bin Shen
Published: June 2021

According to Stokes’ approach, given the gravity anomaly on the geoid as the boundary, a disturbing potential function satisfying some boundary conditions should be solved. The basic requirement is that the disturbing potential function should be harmonic in the region outside the geoid. However, since the normal gravity potential is not defined inside the reference ellipsoid (taking the WGS84 ellipsoid as an example), when the geoid is below the ellipsoidal surface, the disturbing potential function is not harmonic in the whole region outside the geoid, and is not defined on the whole geoid itself. These are theoretical difficulties in Stokes’ approach. To remove these difficulties from Stokes’ approach, this study provides a new formulation of Stokes’ approach. An inner ellipsoid with four fundamental parameters is chosen, two of which, the geocentric gravitational constant and the rotational angular velocity, coincide with the corresponding parameters of the WGS84 ellipsoid. The other two parameters, the semi-major axis and flattening, are different from the corresponding ones of the ellipsoid. Then, the normal gravity potential generated by the inner ellipsoid is determined, by requiring that it holds a constant on the surface of the inner ellipsoid or on the surface of the ellipsoid. With this new formulation, the disturbing potential function is harmonic in the whole region outside the geoid, and the difficulties in Stokes’ approach disappear. The new formulation proposed in this study is also adequate for analogous geodetic boundary-value problems.
IL TERREMOTO DELLO HOKKAIDO DEL 4 MARZO 1952. PARTE II.
Authors: ANTONINO GIRLANDA
Published: June 2021

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On amplitudes of P near the shadow zone
Authors: I. Lehmann
Published: June 2021

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SONDAGGIO ACUSTICO DELLE NUBI
Authors: GUGLIELMO ZANOTELLI
Published: June 2021

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L'EQUILIBRIO IONICO NELLA BASSA ATMOSFERA E LE TEORIE SULLA RICOMBINAZIONE
Authors: BRUNO VITALE
Published: June 2021

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ONDE SUPERFICIALI ATTRAVERSO IL BACINO DELL'ATLANTICO
Authors: P. CALOI  , L. MARCELLI
Published: June 2021

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STRUTTURA GEOLOGICO-SISMICA DELL'EUROPA CENTRO-MERIDIONALE, DELL'ITALIA E DEL MEDITERRANEO CENTRO-OCCIDENTALE, QUALE RISULTA DA RECENTI RICERCHE COMPIUTE IN ITALIA
Authors: PIETRO CALOI
Published: June 2021

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Sulle correlazioni fra densità elettronica ionosferica e attività solare
Authors: F. Mariani
Published: June 2021

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Il livello del mare quale riferimento altimetrico
Authors: S. Polli
Published: June 2021

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RICERCHE SULL'AGITAZIONE MICROSISMICA IN GERMANIA DURANTE LA SECONDA GUERRA MONDIALE
Authors: E. Hardtwig
Published: June 2021

Nel corso dell'unno 1942, dal Ministero dell'aria tedesco del tempo ju presala determinazione di studiare a fondo le relazioni fra microsismi e andamento deltempo. Scopo delle ricerche doveva essere quello di investigare se i dati relativi aimicrosismi potevano servire per la conoscenza della situazione meteorologica e,eventualmente, per la prognostica meteorologica. Sotto la direzione del Prof. Angenheisterdi Gottinga, nella primavera del 1942 iniziarono le ricerche in Gottinga,Stoccarda e Bruxelles.
La struttura della crosta terrestre, con particolare riguardo alle zolle continentali, quale risulta dallo studio dei terremoti e delle grandi esplosioni (Eurasia)
Authors: P. Caloi
Published: June 2021

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TEORIA DEL MICROBAROGRAFO ALFANI
Authors: F. mosetti
Published: June 2021

Per misurare e registrare le oscillazioni barichedi ampiezza piccolissima (fino a miri Hg) con periodi di frazionedi secondo, si usano i microbarografi, o variografi, cbe registranoil flusso dell'aria da un recipiente, per effetto delle variazioni dellapressione esterna.
SULLO SPETTRO DELLE ONDE SISMICHE DESTATE DA ESPLOSIONI (*)
Authors: h. menzel
Published: June 2021

Viene discusso l'effetto d'interferenza, che provoca la variazione dello spettrodelle onde sismiche generate da esplosioni in un mezzo elastico ideale.L'influsso della così detta « Verivitterungszone • (zona in cui originano leonde per urto) sembra essere predominante.
SULL'AUMENTO DI TEMPERATURA NEL MANTELLO DELLA TERRA PER COMPRESSIONE ADIABATICA
Authors: P. E. Valle
Published: June 2021

Viene stabilita una relazione fra la densità, la temperatura e lavelocità delle onde longitudinali e trasversali relativa ad una particolaretrasformazione adiabatica di un solido ideale.L'equazione, applicata al mantello della. Terra, conduce al risultatoche la temperatura in prossimità del nucleo sarebbe circa 1,24volte, la temperatura alla profondità di 1000 km, se la compressionedei materiali fosse avvenuta adiabaticamente.
SULLA COMPOSIZIONE ISOTOPICA DELL'ARGON NEI GAS NATURALI
Authors: G. BOATO  , G. CARERI  , G. NENCINI  , M. SANTANGELO
Published: June 2021

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LIMNOGRAFO A PRESSIONE
Authors: FRANCESCO PERONACI
Published: June 2021

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RILEVAMENTO DELL'ENERGIA DEL VENTO AI FINI DELLA SUA UTILIZZAZIONE MEDIANTE AEROMOTORI
Authors: FRANCESCO PERONACI
Published: June 2021

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CONTRIBUTO ALLO STUDIO DELLE ONDE DI LOVE
Authors: PAOLO EMILIO VALLE
Published: June 2021

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COMPORTAMENTO DI UN'ONDA SONORA ATTRAVERSO UNO STRATO DI NUBE
Authors: GUGLIELMO ZANOTELLI
Published: June 2021

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SUL REGIME PLUVIOMETRICO DI FIRENZE (1832-1949)
Authors: REGINALDO CIANFERONI
Published: June 2021

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RILIEVO SPERIMENTALE GRAVIMETRICO-MAGNETICO NELL'AVAMPAESE DEI COLLI EUGANEI. PARTE I Misure eotvossiane e gravimetriche.
Authors: CARLO MORELI
Published: June 2021

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Engineering seismic demand in the 2012 Emilia sequence: preliminary analysis and model compatibility assessment
Authors: Iunio Iervolino  , Flavia De Luca  , Eugenio Chioccarelli
Published: June 2021

The Emilia 2012 sequence featured seven events of moment magnitude (M) >5, five of which occurred between May 20 and May 29, 2012. These earthquakes were structurally damaging over a wide area. The damage included partial or total collapse of industrial precast reinforced-concrete structures, historical masonry, and mainly nonstructural damage to reinforced-concrete buildings; see Section 8 (Data and sharing resources) for damage report repository. These structural typologies are, in principle, sensitive to different ground-motion intensity measures. For example, loss of support requires significant displacement demand at relatively long periods, while infilling damage is due to the ground-motion amplitude at higher frequencies, and masonry structures are comparatively more sensitive to the cyclic content of ground shaking. Moreover, because events were concentrated in time and space, it can be argued that the cumulative effects of the sequence contributed to the damage. As the current seismic code [C.S.LL.PP. 2008] uses a seismic hazard map [Stucchi et al. 2011] to determine the seismic actions for structural design, when a strong earthquake occurs, probabilistic estimates are understandably questioned for their consistency with respect to the observed ground motion. While it is easy to show that in terms of frequency of exceedance of intensity measures, the hazard can hardly be validated via the records of a single earthquake [e.g., Iervolino 2012], on the other hand, it can certainly be verified whether the observations are compatible or atypical with respect to what is predicted by the tools used in best-practice hazard studies. These issues mostly motivated the preliminary analysis briefly presented in this report; i.e., to investigate the engineering seismic demand (peak and cyclic) and to compare this with the prediction models. Both elastic and inelastic demands were considered. Indeed, the inelastic demands are more important from the structural engineering point of view. […]
Ground effects induced by the 2012 seismic sequence in Emilia: implications for seismic hazard assessment in the Po Plain
Authors: Pio Di Manna  , Luca Guerrieri  , Luigi Piccardi  , Eutizio Vittori  , Doriano Castaldini  , Andrea Berlusconi  , Livio Bonadeo  , Valerio Comerci  , Francesca Ferrario  , Roberto Gambillara  , Franz Livio  , Mauro Lucarini  , Alessandro Maria Michetti
Published: June 2021

Since May 16, 2012, a seismic sequence has affected a wide portion of the Emilia Region (northern Italy), chiefly for the Modena and Ferrara Provinces. The first mainshock (Ml 5.9; focal depth, ca. 6 km) occurred on May 20, 2012, with the epicenter located a few kilometers north of Finale Emilia. A second main shock (Ml 5.8; focal depth, ca. 10 km) occurred on May 29, 2012, about 12 km west of the first earthquake, with the epicenter near Medolla (Figure 1). The seismic sequence has been characterized by five other Ml ≥5 events, and more than 2,300 aftershocks of lower magnitude, until the end July 2012. The distribution of the aftershocks identifies a WNW-ESE-trending zone ca. 40 km long that is characterized by NNE-SSW nearly pure compression, as indicated by the focal mechanisms [e.g., QRCMT 2012]. This report focuses on the many ground effects that were induced by this seismic sequence, as mainly cracks, liquefaction-type phenomena, and hydrological anomalies. The aim is to provide a complete representation of such effects, to: illustrate their type, size and areal distribution; identify the zones in the affected area that were most prone to the occurrence of ground effects (i.e., more susceptible to local geological instability in the case of earthquake occurrence); carry out an independent assessment of the intensities of the earthquakes through the ESI 2007 intensity scale [Guerrieri and Vittori 2007], which is based only on coseismic effects on the natural environment. […]
A GIS-based application for volume estimation and spatial distribution analysis of tephra fallout: a case study of the 122 BC Etna eruption
Authors: Marina Bisson  , Paola Del Carlo
Published: June 2021

In this study, we demonstrate the use of a geo-spatial information system for volume estimation of fallout deposits and for identification of syn-eruptive and post-eruptive depositional mechanisms. For the first time, we present thickness distribution maps, isopachs maps, and fallout deposit volumes for the single stratigraphic units (A-F) of the 122 BC Plinian eruption of Etna, the most powerful eruption of this volcano in historical times. Thickness data collected during the field survey were organized into a geo-referenced database, and several interpolation algorithms were used to calculate the volumes of the six fallout layers of eruption (units A-F). The results are compared with those obtained using the Pyle method, which bases volume calculations on the exponential thickness-decay law of the deposits. Differences in the two methods are analyzed through applying two-dimensional (2D) and 3D geo-statistical analysis to thickness data, with an 'ideal' fallout deposit used as reference. Our approach allowed both identification of stratigraphic sections where the deposits were affected by secondary erosional or accumulation phenomena, and assessment of whether the secondary processes were caused by local morphologic conditions or by variations in eruptive dynamics (e.g., rotation of dispersal axis direction).
Static stress transfer from the May 20, 2012, M 6.1 Emilia-Romagna (northern Italy) earthquake using a co-seismic slip distribution model
Authors: Athanassios Ganas  , Zafeiria Roumelioti  , Konstantinos Chousianitis
Published: June 2021

We model the static stress transfer for the May 2012 northern Italy earthquakes, assuming that failure of the crust occurs by shear. This allows the mechanics of the process to be approximated by the Okada (1992) expressions for displacement and strain fields due to a finite rectangular source in an elastic, homogeneous and isotropic half-space. The slip model of the May 20, 2012, earthquake was derived using empirical Green’s functions and a least-squares inversion scheme of source time functions computed from regional broadband seismological data. The derived model is then incorporated into the computation of Coulomb stress change (ΔCFF) to investigate the possibility that the May 20, 2012, M 6.1 event triggered the second earthquake that occurred on May 29, 2012 (M 5.9). We calculate the Coulomb stress changes for both: (a) optimally oriented planes to regional compression; and (b) planes of fixed orientation assuming that E-W striking, south-dipping thrust faults of the May 29, 2012, type of rupture was a candidate for failure. In both cases, we find that the triggering is promoted as the ΔCFF values in the hypocentral area of the May 29, 2012, earthquake are positive (between 0.61-0.74 bar).

 
Probabilistic forecasting of ionospheric scintillation and GNSS receiver signal tracking performance at high latitudes
Authors: Paul Prikryl  , Veettil Sreeja  , Marcio Aquino  , Periyadan T. Jayachandran
Published: June 2021

At high latitudes, phase scintillation occurs predominantly on the dayside in the ionospheric footprint of the magnetospheric cusp, and in the nightside auroral oval. A new technique of probabilistic forecasting of phase scintillation occurrence relative to the arrival time of high-speed solar wind from coronal holes and interplanetary coronal mass ejections has recently been proposed [Prikryl et al. 2012]. Cumulative probability distribution functions for the phase-scintillation occurrence that are obtained can be specified for low (below-median) and high (above-median) values of various solar wind plasma parameters. Recent advances in modeling of high-speed solar wind and coronal mass ejections, combined with the probabilistic forecasting of scintillation, will lead to improved operational space weather forecasting applications. Scintillation forecasting and mitigation techniques need to be developed to avoid potential costly failures of technology-based Global Navigation Satellite Systems in the near future, in particular during the upcoming solar maximum. The Global Navigation Satellite Systems receiver-tracking performance during severe scintillation conditions can be assessed by the analysis of receiver phase-locked-loop jitter. Tracking jitter maps [Sreeja et al. 2011] offers a potentially useful tool to provide users with expected tracking conditions, if based on scintillation predictions as proposed above. Scintillation indices are obtained from L1 GPS data collected with the Canadian High Arctic Ionospheric Network. Combined with high rate amplitude and phase data, they can be used as input to receiver tracking models to develop scintillation mitigation techniques.
Thirteen years of integrated precipitable water derived by GPS at Mario Zucchelli Station, Antarctica
Authors: Pierguido Sarti  , Monia Negusini  , Claudio Tomasi  , Boyan H. Petkov  , Alessandro Capra
Published: June 2021

Since 1998, the Italian Antarctic Programme has been funding space geodetic activities based on the use of episodic and permanent global positioning system (GPS) observations. As well as their exploitation in geodynamics, these data can be used to sense the atmosphere and to retrieve and monitor its water vapor content and variations. The surface pressure p and temperature Ts at the GPS tracking sites are necessary to compute the zenith hydrostatic delay (ZHD), and consequently, the precipitable water. At sites where no surface information is recorded, the p and Ts values can be retrieved from, e.g., global numerical weather prediction models. Alternatively, the site-specific ZHD values can be computed by interpolation of the ZHD values provided in a grid model (2.5° × 2.0°). We have processed the data series of the permanent GPS site TNB1 (Mario Zucchelli Station, Antarctica) from 1998 to 2010, with the purpose of comparing the use of grid ZHD values as an alternative to the use of real surface records. With these approaches, we estimate almost 7 × 104 hourly values of precipitable water over 13 years, and we find discrepancies that vary between 1.8 (±0.2) mm in summer and 3.3 (±0.5) mm in winter. In addition, the discrepancies of the two solutions show a clear seasonal dependency. Radiosounding measurements were used to derive an independent series of precipitable water. These agree better with the GPS precipitable water derived from real surface data. However, the GPS precipitable water time series is dry biased, as it is ca. 77% of the total moisture measured by the radiosoundings. Both the GPS and radiosounding observations are processed through the most up-to-date strategies, to reduce known systematic errors.
Calculation of the local rupture speed of dynamically propagating earthquakes
Authors: Andrea Bizzarri
Published: June 2021

The velocity at which a propagating earthquake advances on the fault surface is of pivotal importance in the contest of the source dynamics and in the modeling of the ground motions generation. In this paper the problem of the determination of the rupture speed (v_r) is considered. The comparison of different numerical schemes to compute vr from the rupture time (t_r) shows that, in general, central finite differences schemes are more accurate than forward or backward schemes, regardless the order of accuracy. Overall, the most efficient and accurate algorithm is the five–points stencil method at the second–order of accuracy. It is also shown how the determination of t_r can affect v_r ; numerical results indicate that if the fault slip velocity threshold (v_l) used to define t_r is too high (v_l ≥ 0.1 m/s) the details of the rupture are missed, for instance the rupture tip bifurcation occurring for 2–D supershear rupture. On the other hand, for v_l ≤ 0.01 m/s the results appear to be stable and independent on the choice of v_l . Finally, it is demonstrated that in the special case of the linear slip–weakening friction law the definitions of t_r from the threshold criterion on the fault slip velocity and from the achievement of the maximum yield stress are practically equivalent.
Seismological constraints for the dyke emplacement of the July-August 2001 lateral eruption at Mt. Etna volcano, Italy
Authors: Domenico Patanè  , Eugenio Privitera  , Stefano Gresta  , Aybige Akinci  , Salvatore Arpalone  , Graziella Barberi  , Lauro Chiaraluce  , Ornella Cocina  , Salvatore D'amico  , Pasquale De Gori  , Giuseppe Di Grazia  , Susanna Falsaperla  , Ferruccio Ferrari  , Salvatore Gambino  , Elisabetta Giampiccolo  , Horst Langer  , Vincenza Maiolino  , Milena Moretti  , Antonino Mostaccio  , Carla Musumeci  , Davide Piccinini  , Danilo Reitano  , Luciano Scarfì  , Salvatore Spampinato  , Andrea Ursino  , Luciano Zuccarello
Published: June 2021

In this paper we report seismological evidence regarding the emplacement of the dike that fed the July 18 - August 9, 2001 lateral eruption at Mt. Etna volcano. The shallow intrusion and the opening of the eruptive fracture system, which mostly occurred during July 12, and July 18, were accompanied by one of the most intense seismic swarms of the last 20 years. A total of 2694 earthquakes (1 £ Md £ 3.9) were recorded from the beginning of the swarm (July 12) to the end of the eruption (August 9). Seismicity shows the upward migration of the dike from the basement to the relatively thin volcanic pile. A clear hypocentral migration was observed, well constraining the upwards propagation of a near-vertical dike, oriented roughly N-S, and located a few kilometers south of the summit region. Earthquake distribution and orientation of the P-axes from focal mechanisms indicate that the swarm was caused by the local stress source related to the dike intrusion.
Influences of the state of ionospheric background on ionospheric heating effects
Authors: Shuji Hao  , Li Qingliang  , Che haiqin  , Yang Jutao  , Yan Yubo  , Wu Zhensen  , Xu Zhenwen
Published: June 2021

According to the well-performed ionospheric heating experiments at Arecibo in the low latitudes as well as at Tromsø in the high latitudes, the large-scale modification effects are simulated under an assumption of equivalent conditions, i.e., with the same effective radiative power and the same ratio of the heating frequency fHF to the critical frequency of ionospheric F region foF2. The findings are extensively exploited to verify the validation of our model by comparison to the experimental results. Further, a detailed study is carried out on the influences of the background electron density gradient as well as the ratio of fHF to foF2 on heating effects. Conclusions are drawn as follows: under certain conditions, a smaller electron density gradient of background ionospheric F region leads to a better ionospheric heating effect; during over-dense heating, the heating effects are enhanced if the ratio of fHF to foF2 increases, which is slightly limited by the resultant elevation of the reflection height. However, there might be a better ratio range with small values of the ratio of fHF to foF2, e.g., [0.5, 0.7] in the current study. Finally, we analyzed how to select heating parameters efficiently under adverse conditions so to obtain relatively effective results.
Validation strategy for satellite observations of tropospheric reactive gases
Authors: Andreas Richter  , Mark Weber  , John P. Burrows  , Jean-Christopher Lambert  , Anne van Gijsel
Published: June 2021

Over the last twodecades, satellite observations of tropospheric composition have becomepossible using nadir viewing spectrometers operating in the UV, visible, nearinfrared, and thermal infrared spectral range. [...]
The surface layer observed by a high-resolution sodar at DOME C, Antarctica
Authors: Stefania Argentini  , Igor Petenko  , Angelo Viola  , Giangiuseppe Mastrantonio  , Ilaria Pietroni  , Giampietro Casasanta  , Eric Aristidi  , Christophe Genthon
Published: June 2021

One year field experiment has started on December 2011 at the French - Italian station of Concordia at Dome C, East Antarctic Plateau. The objective of the experiment is the study of the surface layer turbulent processes under stable/very stable stratifications, and the mechanisms leading to the formation of the warming events. A sodar was improved to achieve the vertical/time resolution needed to study these processes. The system, named Surface Layer sodar (SL-sodar), may operate both in high vertical resolution (low range) and low vertical resolution (high range) modes. In situ turbulence and radiation measurements were also provided in the framework of this experiment. A few preliminary results, concerning the standard summer diurnal cycle, a summer warming event, and unusually high frequency boundary layer atmospheric gravity waves are presented.
Nowcasting the lightning activity in Peninsular Malaysia using the GPS PWV during the 2009 inter-monsoons
Authors: Wayan Suparta  , Ja’afar Adnan  , Mohd. Alauddin Mohd. Ali
Published: June 2021

The spatial and temporal radio wave delay of the Global Positioning System (GPS) signal can be manipulated to estimate the precipitable water vapor (PWV) which favorable for meteorological applications. A rapid change of the water vapor amount was a precondition for the unbalanced atmospheric charges, which noticeably associated with the development of convective cloud as a lightning chamber. According to this fact, GPS derived PWV will be utilized to nowcasting the lightning event for the next couple of hours. The variances of PWV of four-selected station of the Peninsular Malaysia during the past two inter-monsoons events in May and November 2009 were analyzed. To clarify the response, the changes of PWV in hourly Δ (max-min) before the lightning event was investigated with minimum value 2 mm and is maintained at least three consecutive hours. There are 177 samples were extracted from this method and 69% of the sample showed the lightning occurrence with an average duration was after the six consecutive hours. The lightning day with 2 mm Δ was also higher than the fair weather of 6.3%. These findings suggest that the GPS data can be proposed further as a guide to nowcast the occurrence of lightning activity.
Concordia, Antarctica, seismic experiment for the International Polar Year (CASE-IPY)
Authors: Alessia Maggi  , Maxime Bes de Berc  , Jean-Yves Thoré  , Jean-Jacques Lévêque
Published: June 2021

The CASE-IPY project, part of the larger POLENET initiative of geophysical observations for the International Polar Year, was built on our extensive experience of running seismological stations in Antarctica, both on rock sites (Dumont d’Urville station), and directly on the ice plateau (Concordia station). For CASE-IPY, we deployed 8 temporary seismic stations on the Antarctic plateau: 3 situated near Concordia itself (starting 2008), and the other 5 regularly spaced between Concordia and Vostok (2010-2012), following the maximum in ice topography. The technical problems we have encountered in our field deployments were essentially due to a combination of extreme environmental conditions and isolation of deployment sites. The 3 stations near Concordia were used as test sites to experiment different solutions, and to converge on a design for the 5 main stations. Results from the nearest stations, which transmit data regularly to Concordia, are very promising. The data recorded by our stations will be distributed widely in the scientific community. We expect them to be exploited essentially for structural studies involving Antarctica itself (its ice-cap, crust and lithosphere) via receiver functions, noise correlation, and surface-wave tomography, but also for studies of the Earth’s core.
A declustered earthquake catalog for the Iranian Plateau
Authors: Seyed Hasan Mousavi-Bafrouei  , Noorbakhsh Mirzaei  , Elham Shabani
Published: June 2021

A unified catalog of earthquakes in Iran and adjacent regions (the area bounded in 22º-42ºN and 42º-66ºE) covering the period of 4th century B.C. through 2012 with Mw≥4 is provided. The catalog includes all events for which magnitude have been determined by international agencies and most reliable individual sources. Since the recurrence time of maximum credible earthquake cannot be directly estimated from the mb, empirical formulae are established to convert mb to Ms, mb to Mw and Ms to Mw for each major seismotectonic province separately. The unified catalog is declustered using conjugated distance-time windows. In order to estimate completeness thresholds, magnitude-time (M-T) diagram and Stepp’s method are applied on the declustered catalog for each seismotectonic province. The magnitude of completeness (Mc) decreases with development of local and regional seismic stations. The results of present study are particularly important in seismic hazard analysis in Iran.
P-wave velocity and density structure beneath Mt. Vesuvius: a magma body in the upper edifice?
Authors: Paolo Capuano  , Guido Russo  , Roberto Scarpa
Published: June 2021

A high-resolution image of the compressional wave velocity and density structure in the shallow edifice of Mount Vesuvius has been derived from simultaneous inversion of travel times and hypocentral parameters of local earthquakes and from gravity inversion. The robustness of the tomography solution has been improved by adding to the earthquake data a set of land based shots, used for constraining the travel time residuals. The results give a high resolution image of the P-wave velocity structure with details down to 300-500 m. The relocated local seismicity appears to extend down to 5 km depth below the central crater, distributed into two clusters, and separated by an anomalously high Vp region positioned at around 1 km depth. A zone with high Vp/Vs ratio in the upper layers is interpreted as produced by the presence of intense fluid circulation alternatively to the interpretation in terms of a small magma chamber inferred by petrologic studies. In this shallower zone the seismicity has the minimum energy, whilst most of the high-energy quakes (up to Magnitude 3.6) occur in the cluster located at greater depth. The seismicity appears to be located along almost vertical cracks, delimited by a high velocity body located along past intrusive body, corresponding to remnants of Mt. Somma. In this framework a gravity data inversion has been performed to study the shallower part of the volcano. Gravity data have been inverted using a method suitable for the application to scattered data in presence of relevant topography based on a discretization of the investigated medium performed by establishing an approximation of the topography by a triangular mesh. The tomography results, the retrieved density distribution, and the pattern of relocated seismicity exclude the presence of significant shallow magma reservoirs close to the central conduit. These should be located at depth higher than that of the base of the hypocenter volume, as evidenced by previous studies.
The recent seismicity of Mt. Vesuvius: inference on seismogenic processes
Authors: Luca D’Auria  , Antonietta M. Esposito  , Domenico Lo Bascio  , Patrizia Ricciolino  , Flora Giudicepietro  , Marcello Martini  , Teresa Caputo  , Walter De Cesare  , Massimo Orazi  , Rosario Peluso  , Giovanni Scarpato  , Ciro Buonocunto  , Marco Capello  , Antonio Caputo
Published: June 2021

We have analyzed the recent seismicity of Mt. Vesuvius, with particular emphasis on the period 1999-2012. Since 1972 continuous observations with electromagnetic seismometers allowed the compilation of a detailed earthquake catalogue for the station OVO. Furthermore since 1999 another, more complete, catalogue for the station BKE, closer to the crater, is available. The Gutenberg-Richter distribution of magnitudes shows a temporal decrease of the b-value since 1985, with current values close to 1.0. The temporal pattern of the strain release shows a non-stationary behavior with periods of increased release rates (as in 1989-1990, 1995-1996 and 1999-2000). The spatial distribution of the seismicity consists in two main seismogenic volumes, one with hypocenters clustered below the Mt. Vesuvius crater at depths mostly between 1-6 km, and another with hypocenters clustered within the Gran Cono volcanic edifice, with depths above the sea level. We compare the statistical properties of the seismicity occurring within these two volumes and their spatial and temporal patterns. Moreover we analyze the statistical distribution of focal mechanisms for each volume. Our results point to gravity-induced stresses as the source of the shallow seismicity and of a combined effect of crustal heterogeneities, regional stress and hydrothermal dynamics for the deeper seismicity. Finally we discuss possible future developments of the seismic monitoring system in the light of the past and current seismicity.
A new method for the validation of the GOMOS high resolution temperature profiles products
Authors: Rosario Quirino Iannone  , Stefano Casadio  , Bojan Bojkov
Published: June 2021

This article proposes a new validation method for GOMOS HRTP atmospheric temperature and density profiles, with the aim of detecting and removing 0.2 to 5 km scale vertical structures in order to minimise the impact of atmospheric artefacts in the comparison exercises. The proposed approach is based on the use of the “Morlet” Continuous Wavelet Transformation (CWT), for the characterisation and removal of non-stationary and localised vertical structures, in order to produce wave-free profiles of atmospheric temperature and density. Comparison of wave-free temperature/density profiles and wavy structures profiles with those estimated from a limited number of collocated SHADOZ soundings for the years of 2003, 2004 and 2008, is discussed in detail. First results suggest that the proposed approach could lead to a significantly improved HRTP validation scheme, in terms of reduced uncertainties in the estimated biases. Furthermore, this method may be adopted for the study of the vertical component of gravity waves from high spatial/temporal resolution data.
Analysis of soil radon data in earthquake precursory studies
Authors: Hari Prasad Jaishi  , Sanjay Singh  , Raghavendra Prasad Tiwari  , Ramesh Chandra Tiwari
Published: June 2021

Soil radon data were recorded at two selected sites along Mat fault in Mizoram (India), which lies in the highest seismic zone in India. The study was carried out during July 2011 to May 2013 using LR-115 Type II films. Precursory changes in radon concentration were observed prior to some earthquakes that occurred around the measuring sites. Positive correlation was found between the measured radon data and the seismic activity in the region. Statistical analysis of the radon data together with the meteorological parameters was done using Multiple Regression Method. Results obtained show that the method employed was useful for removing the effect of meteorological parameters and to identify radon maxima possibly caused by seismic activity.
Short-term earthquake forecasting experiment before and during the L’Aquila (central Italy) seismic sequence of April 2009
Authors: Maura Murru  , Jiancang Zhuang  , Rodolfo Console  , Giuseppe Falcone
Published: June 2021

In this paper, we compare the forecasting performance of several statistical models, which are used to describe the occurrence process of earthquakes in forecasting the short-term earthquake probabilities during the L’Aquila earthquake sequence in central Italy in 2009. These models include the Proximity to Past Earthquakes (PPE) model and two versions of the Epidemic Type Aftershock Sequence (ETAS) model. We used the information gains corresponding to the Poisson and binomial scores to evaluate the performance of these models. It is shown that both ETAS models work better than the PPE model. However, in comparing the two types of ETAS models, the one with the same fixed exponent coefficient (alpha) = 2.3 for both the productivity function and the scaling factor in the spatial response function (ETAS I), performs better in forecasting the active aftershock sequence than the model with different exponent coefficients (ETAS II), when the Poisson score is adopted. ETAS II performs better when a lower magnitude threshold of 2.0 and the binomial score are used. The reason is found to be that the catalog does not have an event of similar magnitude to the L’Aquila mainshock (Mw 6.3) in the training period (April 16, 2005 to March 15, 2009), and the (alpha)-value is underestimated, thus the forecast seismicity is underestimated when the productivity function is extrapolated to high magnitudes. We also investigate the effect of the inclusion of small events in forecasting larger events. These results suggest that the training catalog used for estimating the model parameters should include earthquakes of magnitudes similar to the mainshock when forecasting seismicity during an aftershock sequence.
Trace elements mobility in soils from the hydrothermal area of Nisyros (Greece)
Authors: Kyriaki Daskalopoulou  , Sergio Calabrese  , Silvia Milazzo  , Lorenzo Brusca  , Sergio Bellomo  , Walter D'Alessandro  , Konstantinos Kyriakopoulos  , Franco Tassi  , Francesco Parello
Published: June 2021

Nisyros Island, Greece, is a stratovolcano known for its intense hydrothermal activity. On June 2013, during a multidisciplinary field campaign, soil samples were collected in the caldera area to determinate the main mineralogical paragenesis and to investigate the distribution of trace elements concentrations and the possible relationship to the contribution of deep originated fluids. Soil samples were analysed with XRD and for the chemical composition of their leachable (deionized water) and near total (microwave digestion) fraction both for major and trace elements. All data were compared to a local background soil. The results allow to divide the samples in 2 groups: Lakki Plain and Stefanos Crater. The latter, where a fumarolic area is located, shows a mineralogical paragenesis dominated by phases typical of hydrothermal alteration. Their very low pH values (1.9 – 3.4) evidence the strong impact of fumarolic gases which are probably also the cause of strong enrichments in these soils of highly volatile elements like S, As, Se, Bi, Sb, Tl and Te. The soils of the Lakki Plain, being less exposed to the fumarolic activity, show minearalogical and chemical characteristics intermediate between the background soil and those of Stefanos Crater.
Characterization of GPS-TEC in a low-latitude region over Thailand during 2010-2012
Authors: V. Rajesh Chowdhary  , Nitin K. Tripathi  , Sanit Arunpold  , Durairaju Kumaran Raju
Published: June 2021

This paper presents the first results of vertical total electron content (VTEC) data from (1) a dual-frequency GPS receiver installed at the Chiang Mai University in Chiang Mai (CHGM, 18.480 N, 98.570 E) as part of SCINDA (Scintillation Network and Decision Aid) and (2) the International GNSS Service (IGS) station Pathum Wan (CUSV, 13.735 N, 100.533 E) with magnetic latitude of 8.69°N and 3.92°N respectively in Thailand, from August 2010 to July 2012. In the equatorial ionization anomaly (EIA) region, these two stations are separated at a distance of 668 km. Observed GPS-TEC values were found to be the highest between 1500 and 1900 Local Time (LT) throughout the study period at both the stations. The GPS-TEC data from both the stations was plotted diurnal, monthly and seasonal analyses were performed. The equinox (March, April, September, and October) and solstice (January, February, June, July, and December) periods had maximum and minimum diurnal peak variations, respectively, of the GPS-TEC. High TEC values are attributed to extreme solar ultra-violet ionization coupled with upward vertical E×B drift. A comparison of the GPS-TEC data from both the stations for the study period shows that the CHGM station recorded higher values of TEC than the CUSV station because of the formation of an ionization crest over the CHGM station. The GPS-TEC values also exhibited an increasing trend-because of the approach of solar cycle 24. For data validation, the diurnal, monthly, and seasonal variations in the measured TEC were compared with the TEC modelled in the International Reference Ionosphere (IRI) models (IRI-2007 and the recently released IRI-2012 model). The IRI-2007 shows good agreement with the data from 2010 to 2011 from both stations and IRI-2012 agrees well with the data from 2012 onwards compared to IRI-2007.
Recovering of local magnetic K-indices from global magnetic Kp-indices using neural networks: an application to Antarctica
Authors: Antoni Segarra  , Juan José Curto
Published: June 2021

This paper describes a method to obtain local magnetic index, K, from the global index, Kp. Until now, however, for the cases of areas without magnetic observatories, to estimate the geomagnetic activity there, global indices were the only option. The methodology that we used to estimate local index was based on neural networks. This tool has a great potential for processing information from complex systems as in the case of the geomagnetic system. Local K index calculated with this method resulted to be a better option than directly using the global index Kp when we need an indicator of geomagnetic activity in a specific area. The best results of our method were for moderate and high geomagnetic activity, which are of major interest in Space Weather.
Long term continuous radon monitoring in a seismically active area
Authors: Antonio Piersanti  , Valentina Cannelli  , Gianfranco Galli
Published: June 2021

We present the results of a long term, continuous radon monitoring experiment started in April 2010 in a seismically active area, affected during the 2010-2013 data acquisition time window by an intense micro seismic activity and by several small seismic events. We employed both correlation and cross-correlation analyses in order to investigate possible relationship existing between the collected radon data, seismic events and meteorological parameters. Our results do not support the feasibility of a robust one-to-one association between the small magnitude earthquakes characterizing the local seismic activity and single radon measurement anomalies, but evidence significant correlation patterns between the spatio-temporal variations of seismic moment release and soil radon emanations, the latter being anyway dominantly modulated by meteorological parameters variations.