bluuebunny/crossref_metadata_2025 huggingface dataset:
Interfacing between regional and global, electron density height profile
Authors: B. Zolesi  , L. R. Cander
Published: June 2021

A first analysis of the possibility of interfacing regional and global electron density height profile models, over a buffer zone, was performed considering the results obtained using different models such as IRI 90 (Bilitza, 1990), DGR (Di Giovanni et al., 1992) and RAL MPQ (Dick and Bradley, 1992). The differences ?N ?cm3 of electron density as a function of altitude between different models were calculated using monthly median experimental data measured at Rome station and values predicted by URSI, STRM (Zolesi et al., 1993) and EOF (Singer and Dvinskikh, 1991) mapping models for the same point. Composite ionograms are used to roughly evaluate the performances of the three models considered.
Evaluation of 1947-1993 macroseismic information in Portugal using the EMS-92 scale
Authors: A. Paula  , C. S. Oliveira
Published: June 2021

In the present work macroseismic information of the earthquakes felt in Continental Portugal from 1947 to 1993 was evaluated using the EMS-92 intensity scale. Press information, and data in the seismological questionnaires used in this period of time, were used as prime information. Prior intensity assignments were also used in the analysis. Two methodologies -A and B -were followed, according to the type of information available: A) whenever seismological questionnaires or descriptions of effects are accessed this information was analysed leading to an intensity value and to an intensity quality factor; this methodology includes a standardisation of questionnaire evaluation, through the use of conversion keys; B) if only an intensity assignment, in any known scale, existed, then a conversion of intensities was made. The results of these two methodologies are compared and discussed. Based on the above mentioned information a database with 1947-1993 Portuguese seismic information was built up, and a few features of its contents were discussed.
Local seismic cultures: a European research program for the protection of traditional housing stock
Authors: B. Helly
Published: June 2021

The research activity of the Ravello European Center for Cultural Heritage in seismic risk areas is part of the Council of Europe's Major Risks EUR-OPA agreement. The program aims to identify traditional antiseismic building techniques. with a view to subsequent revitalization, tapping know-how within the local community. This requires analysis of the techniques and methods that have developed over the years in local communities. The multidisciplinary research program set up for this purpose has adopted the archeological approach. thereby recognizing that physical and inaterial assets provide a key source of information.
Earthquakes and large block monumental structures
Authors: A. Sinopoli
Published: June 2021

A review of a research program developed in the last fen years into the dynamics of large block structure is presented. The many aspects which characterize the structural behaviour and determine the complexity of the consequent dynamics are briefly discussed. The preliminary mechanical models and first results obtained are also analyzed; they allow to define the direction of the main object of the research in progress.
The 1448 earthquake in Catalonia. Some effects and local reactions
Authors: R. Salicrù i Lluch
Published: June 2021

The May 1448 earthquake. the last destructive one that took place in Catalonia in the Middle Ages, was known chiefly from several chronistic and narrative medieval sources. To these sources I add new previously unknown data proceeding Eroin documentary archival sources in Barcelona, and other data that up to now have been wrongly considered as a consequence of the weak quake recorded in September 1450. They allow us to locate the epicentre in the Vall&s Oriental, around Llinars, to deny the existence of two almost simultaneous earthquakes, and to extend the range of the earthquake damage. to pinpoint them better and to suppose that the effects of the 1448 earthquake were more important than we had previously thought. All this information leads to several reflections on compulsory critical analysis of historical seismic documentary sources in order for them to be useful to historical seismicity. Finally. by the opposition of the three lands of documentary sources that refer to the damage caused by the earthquake in the township of Mataro. I show how natural catastrophes could be manipulated, and the skill of a society in exploiting them to deal with an adverse situation.
Application of numerical simulations for a tentative seismic microzonation of the city of Rome
Authors: D. Fah  , C. Iodice  , P. Suhadolc  , G. F. Panza
Published: June 2021

A hybrid technique, based on mode summation and finite differences, was used to silnulate the ground motion induced in the city of Rome by possible earthquakes occurring in the main seisrnogenetic areas surrounding the city: the Central Apennines and the Alban Hills. The results of the numerical simulations are used for a seismic inicrozonation in the city of Rome, which can be used for the retrofitting of buildings of special social and cultural value. On the basis of our analysis Rome can be divided into six main zones: (1) the edges and (2) the central part of the alluvial basin of the River Tiber; (3) the edges and (4) the central part of the Paleotiber basin; the areas outside the large basins of the Tiber and Paleotiber, where we distinguish between (5) areas without, and (6) areas with a layer of volcanic rocks close to the surface. The strongest amplification effects have to be expected at the edges of the Tiber basin, with maximum spectral amplification of the order of 5 to 6, and strong arnplifications occur inside the entire alluvial basin of the Tiber. The presence of a near-surface layer of rigid material is not sufficient to classify a location as a <> when the rigid material covers a sedimentary complex. The reason is that the underlying sedimentary complex causes amplifications at the surface due to resonance effects. This phenomenon can be observed in the Paleotiber basin, where spectral amplifications in the frequency range 0.4-1.0 Hz reach values of the order of 3 to 4.
Considerations on the assessment of macroseismic intensity
Authors: D. Molin
Published: June 2021

Following a brief overview on the main characteristics of MCS (1930; the most employed in Italy), MSK (1981) and EMS (1992) macroseismic scales, considerations on their validity to underline the severity of damage on buildings are reported and discussed. Observations carried out on damage related to recent Italian earthquakes show that the seismic behaviour of buildings does not fit that provided by the scales, particularly with regard to the relationship <>.
Wooden floors: part of historical antiseismic building systems
Authors: U. Barbisan  , F. Laner
Published: June 2021

The article describes how wooden floors have been used over the centuries as a means of ensuring greater building solidity to ensure against earthquakes or other events that threaten wall stability.
Radon migration in the soils of the Irno Valley (Southern Italy) inferred from radioactive disequilibrium
Authors: S. De Martino  , C. Sabbarese  , P. Gasparini
Published: June 2021

Radon migration along vertical profiles in the soils of Irno River alluvial Valley (Southern Italy) was studied using radioactive disequilibrium between 226 Ra and 210 Pb. Fractional Radon loss, migration length, diffusion and emanation coefficient and Radon flux density were determined. Our results are in agreement with a migra- tion model by simple diffusion. The migration parameters are within typical values, except the Radon flux density, which is about one order of magnitude higher than the values reported in literature. The values of fractional Radon loss are sensitive to changes in the physical properties of the soil.
Analysis of strong-motion data of the 1990 Eastern Sicily earthquake
Authors: M. Di Bona  , M. Cocco  , A. Rovelli  , R. Berardi  , E. Boschi
Published: June 2021

The strong motion accelerograms recorded during the 1990 Eastern Sicily earthquake have been analyzed to investigate source and attenuation parameters. Peak ground motions (peak acceleration, velocity and displacement) overestimate the values predicted by the empirical scaling law proposed for other Italian earthquakes, suggesting that local site response and propagation path effects play an important role in interpreting the observed time histories. The local magnitude, computed from the strong motion accelerograms by synthesizing the Wood-Anderson response, is ML = 5.9, that is sensibly larger than the local magnitude estimated at regional distances from broad-band seismograms (ML = 5.4). The standard omega-square source spectral model seems to be inadequate to describe the observed spectra over the entire frequency band from 0.2 to 20 Hz. The seismic moment estimated from the strong motion accelerogram recorded at the closest rock site (Sortino) is Mo = 0.8 x 1024 dyne.cm, that is roughly 4.5 times lower than the value estimated at regional distances (Mo = 3.7 x 1024 dyne.cm) from broad-band seismograms. The corner frequency estimated from the accelera- tion spectra i.5 J; = 1.3 Hz, that is close to the inverse of the dUl.ation of displacement pulses at the two closest recording sites. This value of corner tì.equency and the two values of seismic moment yield a Brune stress drop larger than 500 bars. However, a corner frequency value off; = 0.6 Hz and the seismic moment resulting from regional data allows the acceleration spectra to be reproduced on the entire available frequency band yielding to a Brune stress drop of 210 bars. The ambiguity on the corner frequency value associated to this earthquake is due to the limited frequency bandwidth available on the strong motion recordil1gs. Assuming the seismic moment estimated at regional distances from broad-band data, the moment magnitude for this earthquake is 5.7. The higher local magnitude (5.9) compared with the moment magnitude (5.7) is due to the weak regional attenuation. Beside this, site amplifications due to surface geology have produced the highest peak ground motions among those observed at the strong motion sites.
The improved DGR analytical model of electron density height profile and total electron content in the ionosphere
Authors: S. M. Radicella  , M. L. Zhang
Published: June 2021

Tests of the analytical model of the electron density profile originally proposed by G, Di Giovanni and S.M. Radicella (DGR model) have shown the need to introduce improvements in order to obtain a model able to reproduce the ionosphere in a larger spectrum of geophysical and time conditions. The present paper reviews the steps toward such progress and presents the final formulation of the model. It gives also a brief re- view of tests of the improved model done by different authors.
A new catalogue of earthquakes in the historical Armenian area from antiquity to the 12th century
Authors: E. Guidoboni  , G. Traina
Published: June 2021

The present contribution describes the method of work, the types of source materia] used, and the historio- graphical and historico-eismic tradition of Armenia. The catalogue' s territorial frame of reference is that of socalled historical Armenia (which included part of present Eastern Turkey, and part of present Azerbaijan). The sources belong to different languages and cultures: Armenian, Syriac, Greek, Arab, Persian and Georgian. A comparison of the local sources with those belonging to other cultures enab]es the historical and seismological I"adition of the Mediterl'anean to be "linked" with that of the Iranian p]ateau, traditionally considered as two separate areas. We analyzed historical events listed in the most recent catalogues of earthquakes in the Armenian area compiled by Kondorskaya and Shebalin (1982) and Karapetian (1991). Important and valuable though these catalogues are, they are in need of revision. We found evidence for six hitherto unrecorded seismic events. Numerous errors of dating and location have been corrected, and several new localities and seismic effects have been evidenced. Each modification of the previous catalogues has been documented on the hasis of the historiographical and literary sources and the data from the written sources have been linked with those concerning the history of Armenian cities and architecture (monasteries, churches, episcopal complexes). On the whole. the revised earthquakes seem underestimated in the previous catalogues. The aim of this catalogue is to make a contribution to the knowledge of historical seismicity in Armenia, and at the same time to underline the specific nature of the Armenian case, thus avoiding a procedure which has generally tended to place this area in a marginal position, within the wider field of other research on historical earthquakes.
Fault geometry and earthquake mechanics
Authors: D. J. Andrews
Published: June 2021

Earthquake mechanics may be determined by the geometry of a fault system. Slip on a fractal branching fault surface can explain: 1) regeneration of stress irregularities in an earthquake; 2) the concentration of stress drop in an earthquake into asperities; 3) starting and stopping of earthquake slip at fault junctions, and 4) self-similar scaling of earthquakes. Slip at fault junctions provides a natural realization of barrier and asperity models without appealing to variations of fault strength. Fault systems are observed to have a branching fractal structure, and slip may occur at many fault junctions in an earthquake. Consider the mechanics of slip at one fault junction. In order to avoid a stress singularity of order 1/r, an intersection of faults must be a triple junction and the Burgers vectors on the three fault segments at the junction must sum to zero. In other words, to lowest order the deformation consists of rigid block displacement, which ensures that the local stress due to the dislocations is zero. The elastic dislocation solution, however, ignores the fact that the configuration of the blocks changes at the scale of the displacement. A volume change occurs at the junction; either a void opens or intense local deformation is required to avoid material overlap. The volume change is proportional to the product of the slip increment and the total slip since the formation of the junction. Energy absorbed at the junction, equal to confining pressure times the volume change, is not large enongh to prevent slip at a new junction. The ratio of energy absorbed at a new junction to elastic energy released in an earthquake is no larger than P/µ where P is confining pressure and µ is the shear modulus. At a depth of 10 km this dimensionless ratio has th value P/µ= 0.01. As slip accumulates at a fault junction in a number of earthquakes, the fault segments are displaced such that they no longer meet at a single point. For this reason the volume increment for a given slip increment becomes larger. A juction with past accumulated slip ??0 is a strong barrier to earthquakes with maximum slip um < 2 (P/µ) u0 = u0/50. As slip continues to occur elsewhere in the fault system, a stress concentration will grow at the old junction. A fresh fracture may occur in the stress concentration, establishing a new triple junction, and allowing continuity of slip in the fault system. The fresh fracture could provide the instability needed to explain earthquakes. Perhaps a small fraction (on the order of P/µ) of the surface that slips in any earthquake is fresh fracture. Stress drop occurs only on this small fraction of the rupture surface, the asperities. Strain change in the asperities is on the order of P/µ. Therefore this model predicts average strais change in an earthquake to be on the order of (P/µ)2 = 0.0001, as is observed.
Monitoring 222 Rn in soil gas of Garfagnana (Tuscany) aimed at earthquake prediction
Authors: O. Balducci  , G. Bigazzi  , R. Cioni  , M. Leonardi  , C. Meletti  , P. Norelli  , A. Pescia  , G. Taddeucci
Published: June 2021

222 Rn concentration in soil gas from nineteen stations of Garfagnana valley (Central ltaly) was continuously monitored from December 1990 to May 1993. 222 Rn activity was measured by solid state nuclear track detector (SSNTD). Tracks detected by spark-counter and by optical microscope were proportionally constant for track densities lower than 2500 tracks/cm2. Since time variations in track density both for the same monitoring station and for different stations are significanfly higher than fluctuations in the experimental conditions, the validity of spark-counter for radon activity measurements is confirmed. Data collected in the period of monitoring indicate significant seasonal variations in radon concentration for every monitoring station. Moreover, the soil characteristics play an important role in determining the observed patterns. No significant correlation could be found between radon emission and seismicity. However, it should be noted that no earthquake with a magnitude higher than 3.5 occurred in Garfagnana during the monitoring period.
TEC and f0F2 comparison
Authors: P. Spalla  , L. Cairolo
Published: June 2021

Following an investigation on the calibration of Faraday Rotation measurements by the slab thickness method, several interesting results have been obtained concerning the limits of application of TEC data in f0F2 modelling at middle latitudes.
The MEDNET Program
Authors: E. Boschi  , A. Morelli
Published: June 2021

MEDNET is a network of very-broadband, high resolution seismographic stations primarily installed in countries of the Mediterranean area. Support for stations in developing countries comes from World Laboratory (Lausanne), a non-governmental international organisation. The project started in 1989 and now lists 15 active stations. It kept a special emphasis on the Mediterranean area, as its main target area, but also included stations in Nepal and Antarctica by following other Italian national initiatives. Three stations are in cooperation with University of Trieste (TTE), GEOSCOPE (SSB), and IRIS/GSN (TBT). Stations in Antarctica are installed and maintained in the framework of the Italian Antarctic Program (PNRA).
Accurate determination of phase arrival times using autoregressive likelihood estimation
Authors: G. Kvaerna
Published: June 2021

We have investigated the potential automatic use of an onset picker based on autoregressive likelihood estimation. Both a single component version and a three component version of this method have been tested on data from events located in the Khibiny Massif of the Kola peninsula, recorded at the Apatity array, the Apatity three component station and the ARCESS array. Using this method, we have been able to estimate onset times to an accuracy (standard deviation) of about 0.05 s for P-phases and 0.15 0.20 s for S phases. These accuracies are as good as for analyst picks, and are considerably better than the accuracies of the current onset procedure used for processing of regional array data at NORSAR. In another application, we have developed a generic procedure to reestimate the onsets of all types of first arriving P phases. By again applying the autoregressive likelihood technique, we have obtained automatic onset times of a quality such that 70% of the automatic picks are within 0.1 s of the best manual pick. For the onset time procedure currently used at NORSAR, the corresponding number is 28%. Clearly, automatic reestimation of first arriving P onsets using the autoregressive likelihood technique has the potential of significantly reducing the retiming efforts of the analyst.
Automated detection and association of surface waves
Authors: R. G. North  , C. R. D. Woodgold
Published: June 2021

An algorithm for the automatic detection and association of surface waves has been developed and tested over an 18 month interval on broad band data from the Yellowknife array (YKA). The detection algorithm uses a conventional STA/LTA scheme on data that have been narrow band filtered at 20 s periods and a test is then applied to identify dispersion. An average of 9 surface waves are detected daily using this technique. Beamforming is applied to determine the arrival azimuth; at a nonarray station this could be provided by poIarization analysis. The detected surface waves are associated daily with the events located by the short period array at Yellowknife, and later with the events listed in the USGS NEIC Monthly Summaries. Association requires matching both arrival time and azimuth of the Rayleigh waves. Regional calibration of group velocity and azimuth is required. . Large variations in both group velocity and azimuth corrections were found, as an example, signals from events in Fiji Tonga arrive with apparent group velocities of 2.9 3.5 krn/s and azimuths from 5 to + 40 degrees clockwise from true (great circle) azimuth, whereas signals from Kuriles Kamchatka have velocities of 2.4 2.9 km/s and azimuths off by 35 to 0 degrees. After applying the regional corrections, surface waves are considered associated if the arrival time matches to within 0.25 km/s in apparent group velocity and the azimuth is within 30 degrees of the median expected. Over the 18 month period studied, 32% of the automatically detected surface waves were associated with events located by the Yellowknife short period array, and 34% (1591) with NEIC events; there is about 70% overlap between the two sets of events. Had the automatic detections been reported to the USGS, YKA would have ranked second (after LZH) in terms of numbers of associated surface waves for the study period of April 1991 to September 1992.
Intelligent post processing of seismic events
Authors: T. Kvaerna  , F. Ringdal
Published: June 2021

The Intelligent Monitoring Systern (IMS) currently provides for joint processing of data from six arrays located in Northern and Central Europe. From experience with analyst review of events automatically defined by the IMS, we bave realized that the quality of the automatic event locations can be significantly improved if the event intervals are reprocessed with signal processing pararneters tuned to phases from events in the given region. The tuned processing parameters are obtained from off line analysis of events located in the region of interest. The primary goal of such intelligent post processing is to provide event definitions of a quality that minimizes the need for subsequent manual analysis. The first step in this post processing is to subdivide the arca to be monitored in order to identify sites of interest. Clearly, calibration will be the easiest and potential savings in manpower are the largest for areas of high, recurring seismicity. We bave identified 8 mining sites in Fennoscandia/NW Russia and noted that 65.6% of the events of ML > 2.0 in this region can be associated with one of these sites. This result is based on 1 year and a half of data. The second step is to refine the phase arrival and azimuth estimates using frequency filters and processing parameters that are tuned to the initial event location provided by the IMS. In this study, we have analyzed a set of 52 mining explosions from the Khibiny Massif mining area in the Kola peninsula of Russia. Very accurate locations of these events bave been provided by the seismologists from the Kola Regional Seismology Centre. Using an autoregressive likelihood technique we have been able to estimate onset times to an accuracy (standard deviation) of about 0.05 s for P phases and 0.15 0.20 s for S phases. Using fixed frequency bands, azimuth can be estimated to an accuracy (one standard deviation) of 0.9 degrees for the ARCESS array and 3 4 degrees for the small array recently established near Apatity on the Kola peninsula. The third step in the post processing is a relocation of the event, using refined arrivai times and recomputed azimuths from broad band flk analysis. By introducing region specific travel time corrections, a median error of 1.4 km from the reported location has been obtained. This should be compared to the median error of 10.8 km for the automatie IMS processing for these events. This improvement in location accuracy clearly demonstrates the usefulness of the intelligent post processing approach.
Amplitude-distance curves of P, S and L waves in Central Balkans for short and medium period seismographs
Authors: L. Christoskov
Published: June 2021

The basic principles for deriving the amplitude-distance curves or calibrating functions at short epicentral distances for the central part of the Balkan region are described. A procedure for unification of magnitude determinations for P, S and L waves is applied on the basis of the teleseismic surface wave magnitude scale. The results for short and medium period seismographs are presented.
Further tests of the IRI and DGR model ionospheres
Authors: K. J. Kecic  , P. A. Bradley  , L. R. Cander  , M. I. Dick  , B. Zolesi
Published: June 2021

The present study discusses and compares the IRI and DGR ionospheric models using N(h) profiles obtained during a high solar activity period at South Uist ionosonde station. After inversion, N(h) profiles obtained from ionograms at South Uist have been compared with those derived from the IRI-90 and DGR ionospheric models. A small data set has been selected such that both geomagnetically quiet and disturbed conditions are represented. The importance of further comparisons with additional sets of N(h) profiles under different solar-geophysical conditions and at more stations has been recognized.
Low ionospheric observations by means of the software receiver for Omega signal
Authors: C. Bianchi  , L. Ciraolo  , C. Scotto
Published: June 2021

Two receiving stations of Omega signal (10-14 kHz in the lower end of the VLF band) have been installed in Rome and Florence to record phase and amplitude of signals transmitted by the stations of Norway, Liberia and La Reunion. The receiving stations are equipped with a multifrequency software receiver that is a useful tool to investigate the low ionosphere. The night-day phase changes along the paths will be shown in the quiet and disturbed days for various epochs of the year. Under quiet conditions there are marked variations in the D-region due to the effects of diurnal and seasonal changes in solar illumination. In addition, data from disturbed periods are presented to show the relation between propagation parameters and solar ionizing.
Regional study of the ionosphere quietness over Europe
Authors: T. L. Gulyaeva  , I. Stanislawska
Published: June 2021

Regional catalogues of the ionospherically disturbed and quiet days are developed on the basis of the analysis of vertical-incidence sounding data over European area during 1964-1990. This paper presents the results obtained by comparing and combining two regional catalogues of the ionospheric disturbed and quiet days into one definitive catalogue recommended for implementation in the PRIME oriented and other studies. According to the criteria applied to the F region peak parameters, only 10 to 20% days per year manifest quietness of acceptable level. Comparison of ionospherically quiet days with geomagnetically quiet periods during 1976-1988 shows coincidence of quiet days in both fields not more than 30% of times considered. Conventional practice of analysis of the ionosphere state by comparing it with the geomagnetic conditions should be forerun by specification of the proper ionospheric quiet and disturbed periods.
Integration of high resolution geophysical methods. Detection of shallow depth bodies of archaeological interest
Authors: F. Cammarano  , P. Mauriello  , D. Patella  , S. Piro  , F. Rosso  , L. Versino
Published: June 2021

A combined survey using ground penetrating radar, self-potential, geoelectrical and magnetic methods has been carried out to detect near-surface tombs in the archaeological test site of the Sabine Necropolis at Colle del Forno, Rome, Italy. A 2D data acquisition mode has been adopted to obtain a 3D image of the investigated volumes. The multi-methodological approach has not only demonstrated the reliability of each method in delineating the spatial behaviour of the governing parameter, but mainly helped to obtain a detailed physical image closely conforming to the target geometry through the whole set of parameters involved.
Piezomagnetic effects induced by artificial sources at Mt. Vesuvius (Italy): preliminary results of an experimental survey
Authors: C. Del Negro  , E. Armadillo  , E. Bozzo  , L. Cafarella  , A. Meloni  , R. Napoli  , A. Zirizzotti
Published: June 2021

In order to put new constrains on magnetic effects associated with mechanical stresses, high frequency monitoring of the geomagnetic field was carried out during a seismic tomography experiment (TOMOVES'96 project) at Mt. Vesuvius. Eight proton precession and one Cesium magnetometers were installed along a profile on the SW flank of the volcano to observe possible magnetic changes induced by explosions. Measurements were performed at different sampling frequencies (10 Hz, 0.5 Hz and 0.1 Hz). A remarkable change in the intensity of the magnetic field was observed in only one case. The magnetic transient lasted 12-13 min, reaching the maximum amplitude of slightly less than 15 nT.
A broadband two axis flux-gate magnetometer
Authors: P. Palangio
Published: June 2021

A broadband two axis flux-gate magnetometer was developed to obtain high sensitivity in magnetotelluric measurements. In magnetotelluric sounding, natural low frequency electromagnetic fields are used to estimate the conductivity of the Earth's interior. Because variations in the natural magnetic field have small amplitude(10-100 pT) in the frequency range 1 Hz to 100 Hz, highly sensitive magnetic sensors are required. In magnetotelluric measurements two long and heavy solenoids, which must be installed, in the field station, perpendicular to each other (north-south and east-west) and levelled in the horizontal plane are used. The coil is a critical component in magnetotelluric measurements because very slight motions create noise voltages, particularly troublesome in wooded areas; generally the installation takes place in a shallow trench. Moreover the coil records the derivative of the variations rather than the magnetic field variations, consequently the transfer function (amplitude and phase) of this sensor is not constant throughout the frequency range 0.001-100 Hz. The instrument, developed at L'Aquila Geomagnetic Observatory, has a flat response in both amplitude and phase in the frequency band DC-100 Hz, in addition it has low weight, low power, small volume and it is easier to install in the field than induction magnetometers. The sensivity of this magnetometer is 10 pT rms.
P- waves reflected from the "20" discontinuity" beneath the Mediterranean region
Authors: A BOTTARI  , B. FEDERICO
Published: June 2021

The observed travel-times of the P-waves for twenty shallow, intermediate, and deep earthquakes, with epicenters in the Mediterranean area, are used in order to analyze some characteristics of the upper mantle. A first- order discontinuity, identifiable as the "20° discontinuity", is found at a depth of 505 ± 16 km in the area underneath the Mediterranean basin. The velocity contrast is equal to 12% (above T'= 8.9 km/sec; below V= 9.97 km/sec). Assuming that this discontinuity gives rise to reflected P-waves (PdP), the travel times of these waves are calculated for various hypocentral depths. The observation of impulses identified as PdP on the seismograms of Messina supports this hypothesis. This result and its implications are discussed in the contest of the conclusions of various authors who locate a P-wave velocity-discontinuity at different depths between 400 and 580 km. Finally, particular emphasis is given to the regional character of the analyzed structures in question.
Attività sismica e neotettonica della Valle del Belice
Authors: A. BOTTARI
Published: June 2021

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Italian Magnetic Network and magnetic reference fields at 2010.0
Authors: Guido Dominici  , Antonio Meloni  , Angelo Di Ponzio  , Massimo Miconi
Published: June 2021

The Istituto Nazionale di Geofisica e Vulcanologia (INGV) has systematically undertaken the task of making measurements of the Earth's magnetic field in Italy. By tradition and because of the elongated geometric shape of our peninsula and islands, in Italy, a grid of more than 110 points, called the first order repeat stations, with an average spacing around 55-60 km, is in operation. Over this grid the measurements are repeated regularly, every 5 years. A survey of 131 repeat stations of the Italian Magnetic Network (including 2 observatories, 11 stations in Albania, 3 stations in Corsica and 1 in Malta) was carried out between 2009 and 2010 with the main purpose of updating our magnetic cartography. We describe the characteristics of magnetic first and second order networks, the magnetic measurements and the data reduction procedure. In agreement with the recommendations of MagNetE Committee, we report new repeat station data measured and reduced at 2010.0. An analytical expression, a second order polynomial, in latitude and longitude for the field elements, was determined, and coefficients for 2010.0 and average secular variation over the period 2005-2010, were obtained. The new maps for Italy, for D, F, H and Z at the epoch 2010.0, are shown. A selection of stations from the Italian Magnetic Network, based on their low values of anomaly with respect to a 'normal' field, is also proposed for future surveys.
On the crustal bias of repeat stations in Romania
Authors: Venera Dobrica  , Crisan Demetrescu  , Razvan Greculeasa  , Anca Isac
Published: June 2021

A magnetic induction model has been applied to recordings obtained in 2010 during the field campaigns for geomagnetic measurements at the 26 repeat stations of the Romanian secular variation network. The model is based on the observation that a variable external magnetic field induces a response of the Earth's interior not only by electromagnetic induction, but also by magnetic induction in the magnetic rocks above the Curie temperature. The model computes coefficients of a linear relationship between recorded values of a certain geomagnetic element (X, Y, Z, or F) at the repeat station and recorded X, Y, Z values at a reference station (in this case, SUA observatory). Coefficients depend on magnetic permeabilities of rocks beneath the station and stand as a proxy for the anomaly bias characterizing the site. Maps of the lateral variation of this type of information were obtained and discussed.
Influence of solar activity on magnetic network measurements
Authors: Roberta Tozzi  , Guido Dominici  , Paola De Michelis  , Antonio Meloni
Published: June 2021

The influence of solar activity on magnetic measurements taken during the Italian repeat station surveys performed in 1999/2000 and 2009/2010 has been investigated. A method to estimate the difference between the 2000.0 and 2010.0 surveys in terms of the "residual" (i.e. not completely reduced) external contribution is proposed. This method is also based on the removal of the contribution due to the magnetic field of internal origin by means of CHAOS3 model from magnetic repeat station measurements. The origin of the observed differences is interpreted in terms of the very different level of solar activity between 2000.0 and 2010.0. Indeed, results seem to suggest that differences could be attributed to the enhanced ring current intensity during a phase of solar maximum. The investigation of the spatial patterns of these differences suggests that they could be reduced by introducing a larger number of variometer stations, especially during surveys performed under conditions of high solar activity.
Tectonic blocks and suture zones of eastern Thailand: evidence from enhanced airborne geophysical analysis
Authors: Arak Sangsomphong  , Dhiti Tulyatid  , Thanop Thitimakorn  , Punya Charusiri
Published: June 2021

Airborne geophysical data were used to analyze the complex structures of eastern Thailand. For visual interpretation, the magnetic data were enhanced by the analytical signal, and we used reduction to the pole (RTP) and vertical derivative (VD) grid methods, while the radiometric data were enhanced by false-colored composites and rectification. The main regional structure of this area trends roughly in northwest-southeast direction, with sinistral faulting movements. These are the result of compression tectonics (sigma_1 in an east-west direction) that generated strike-slip movement during the pre Indian-Asian collision. These faults are cross-cut by the northeast-southwest-running sinistral fault and the northwest-southeast dextral fault, which occurred following the Indian-Asian collision, from the transpession sinistral shear in the northwest-southeast direction. Three distinct geophysical domains are discernible; the Northern, Central and Southern Domains. These three domains correspond very well with the established geotectonic units, as the Northern Domain with the Indochina block, the Central Domain with the Nakhonthai block, the Upper Southern Sub-domain with the Lampang-Chaing Rai block, and the Lower Southern Sub-domain with the Shan Thai block. The Indochina block is a single unit with moderate radiometric intensities and a high magnetic signature. The direction of the east-west lineament pattern is underlain by Mesozoic non-marine sedimentary rock, with mafic igneous bodies beneath this. The Nakhonthai block has a strong magnetic signature and a very weak radiometric intensity, with Late Paleozoic-Early Mesozoic volcanic rock and mélange zones that are largely covered by Cenozoic sediments. The boundaries of this block are the southern extension of the Mae Ping Faults and are oriented in the northwest-southeast direction. The Lampang-Chaing Rai and Shan Thai blocks, with very weak to moderate magnetic signatures and moderate to very strong radiometric intensities are dominated by marine clastic and igneous rocks or a northwest-southeast trending deformation zone of inferred Precambrian complexes, respectively. It is suggested that these tectonic plates collided against one another in a west-east direction.
Ethics in disaster management
Authors: Surya Parkash
Published: June 2021

In any profession, a basic set of moral values needs to be followed to comply with what we call ethics. Geoscientists have significant roles to play, more particularly in the field of geohazards, to appraise society about the possibilities of natural hazards such as landslides, avalanches, floods, volcanoes, and earthquakes. Geoscientists cannot only assess these hazards, but they can also estimate the potential consequences if these hazards occur in a given place and at a given time. However, sometimes it has been found that the credibility of geoscientists among society and government is lost, due to some unethical practices for short-term gain, or due to incorrect understanding of geological phenomena. Some of the hazards that cannot be predicted with the existing capabilities have been forecast by some pseudo-geoscientists, to draw social/ media attention, thereby bringing the reputation of the profession into disrepute. There is the need to be fair enough to accept the limitations of our profession in providing information about natural hazards that are not yet fully understood by the professionals themselves. More specifically, the predictions related to earthquakes have drawn the attention of society as well as media in the developing countries where the ‘common’ people have different perceptions. Most often, popular myths take over scientific facts among the public, and this can lead to rumors about natural hazards. This article will mention some cases of rumors about natural disasters, and particularly earthquakes, and the response of society, media and government. It emphasizes the role of geoscientists as the ethical responsibility to inform the public about the actual situations and the geohazards, to avoid panic caused by rumors from non-specialists or hyperactive pseudo experts. This article indicates the recent rumors about a lake outburst, flash floods, and volcanic activities after a moderate earthquake (M 6.9, September 18, 2011) in the Sikkim State of India, and considers the actions taken by the geoscientific community to correctly inform people about the real situation.
PROSPETTO DELLE RICERCHE PER "FORZE ENDOGENE" IN VARIE REGIONI DEL MONDO DURANTE L'ULTIMO TRENTENNIO
Authors: MERCURINO SAPPA
Published: June 2021

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Continuous SO2 flux measurements for Vulcano Island, Italy
Authors: Fabio Vita  , Salvatore Inguaggiato  , Nicole Bobrowski  , Lorenzo Calderone  , Bo Galle  , Francesco Parello
Published: June 2021

The La Fossa cone of Vulcano Island (Aeolian Archipelago, Italy) is a closed conduit volcano. Today, Vulcano Island is characterized by sulfataric activity, with a large fumarolic field that is mainly located in the summit area. A scanning differential optical absorption spectroscopy instrument designed by the Optical Sensing Group of Chalmers University of Technology in Göteborg, Sweden, was installed in the framework of the European project "Network for Observation of Volcanic and Atmospheric Change", in March 2008. This study presents the first dataset of SO2 plume fluxes recorded for a closed volcanic system. Between 2008 and 2010, the SO2 fluxes recorded showed average values of 12 t.d–1 during the normal sulfataric activity of Vulcano Island, with one exceptional event of strong degassing that occurred between September and December, 2009, when the SO2 emissions reached up to 100 t.d–1.
DENSITA ELETTRONICA NELL'ALTA ATMOSFERA E INTERPRETAZIONE DELLE CURVE h' (f) DELL'ALTEZZA VIRTUALE DELLA IONOSFERA. Parte II
Authors: F. MARIANI
Published: June 2021

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Interpreting the interseismic deformation of the Altotiberina Fault (central Italy) through 2D modelling
Authors: Debora Finocchio  , Salvatore Barba  , Stefano Santini  , Antonella Megna
Published: June 2021

The Altotiberina low-angle normal fault in central Italy has been a focus of many recent studies. Although the existence of this fault has long been known, its seismicity and relationship to other faults are still debated. We present a 2D elastoplastic finite-element model that reproduces the interseismic deformation of the Altotiberina Fault. The model predictions are compared to observed geodetic velocities, stress orientations and geological data. The influence of the Altotiberina Fault on interseismic evolution is tested by building several models with different boundary conditions. The best model is 180 km long, 40 km deep and contains two layers with different rheological parameters, two ramps, two faults and four freely slipping segments. The main factors contributing to the large-scale interseismic deformation include basal traction, rheology and the Altotiberina Fault itself, whereas the local, small-scale variations are due to two secondary high-angle faults.
PRIMO CONTRIBUTO PER UNA RETE GRAVIMETRICA FONDAMENTALE IN ITALIA
Authors: CARLO MORELI
Published: June 2021

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LE PRINCIPALI IPOTESI SULL'ISOSTASIA
Authors: C. AQUILINA
Published: June 2021

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UNA RELAZIONE DIRETTA FRA LA VELOCITÀ DELLE ONDE ELASTICHE E LA DENSITÀ NELL'INTERNO DELLA TERRA
Authors: PAOLO EMILIO VALLE
Published: June 2021

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Differenze strutturali tra Alpi meridionali e Valle Padana
Authors: P. Caloi
Published: June 2021

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La "magnitudo unificata" per i terremoti a profondità normale e la "magnitudo" dei terremoti profondi per la stazione sismica di Roma
Authors: D. Di Filippo  , L. Marcelli
Published: June 2021

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UEBER DAS SPEIVTRUM SEISMISCHER WELLEN, DIE DURCH SPRENGUNGEN ERZEUGT WERDEN
Authors: h. menzel
Published: June 2021

Es werden eiiiige Interferenzejfekte diskutiert, ivelche in einemideal elastischen Medium das Spektrum sprengseimischer IT eli e ri ver-(inderà. Der Einfluss der sog. Verivitterungszone scheint am bedeutendstenzu sein.
SULLA ORIGINE DEI MICROSISMI DEL MEDITERRANEO
Authors: M. giorgi  , e. rosini
Published: June 2021

La nota contiene i risultati di indagini particolareggiate condottepresso l'Istituto Nazionale di Geofisica con la collaborazione del ServizioMeteorologico dell' Aeronautica sul problema dell' origine dei microsismi.Lo studio concerne fondamentalmente i tnicrosismi aventiorigine nel Mediterraneo perché questo è il settore per cui maggioreera la abbondanza dei dati meteorologici e di più diretto controllo.L'osservazione continua di oltre tre anni conferma oramai il risultatopiù importante: i microsismi di origine mediterranea non sono indiretta correlazione con i fronti bensì vengono generati nelle zone,in mare aperto, interessale da nuclei di tendenza barometrica positiva.Si riporta, a titolo di esempio, la documentazione relativa ad alcunetempeste microsismiche. Si dà poi una interpretazione delle modalitàdi generazione dei microsismi stessi e della trasmissione dellaenergia dall'atmosfera, attraverso le masse marine, al fondo solido dell'Oceano.Ricerche estese all'analisi dei sondaggi termodinamici stanno adindicare che l'effetto massimo si ha quando lo spessore della massafredda turbolenta è fra 1 e 3 km.
LE SESSE DEL LAGO DI ISEO. Parte II
Authors: FRANCESCO PERONACI
Published: June 2021

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BEITRÀGE ZUR THEORIE DER SEICHES IN ZUSAMMENGESETZTEN SEEBECKENSYSTEMEN
Authors: GERHARD NEUMANN
Published: June 2021

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EFFETTI DELL'ATTRITO INTERNO SULLA PROPAGAZIONE DELLE ONDE DI LOVE
Authors: PAOLO EMILIO VALLE
Published: June 2021

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UN METODO PER LA DETERMINAZIONE DELL'ETÀ' DELLA TERRA
Authors: C. FESTA  , M. SANTANGELO
Published: June 2021

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Sicily and southern Calabria focal mechanism database: a valuable tool for local and regional stress-field determination
Authors: Luciano Scarfì  , Alfio Messina  , Carmelo Cassisi
Published: June 2021

In this work, we present a new catalog of focal mechanisms calculated for earthquakes recorded in Sicily and southern Calabria. It comprises about 300 solutions, for events with magnitudes ranging from 2.7 to 4.8 that occurred from 1999 to 2011. We used P-wave polarities to compute the fault-plane solutions. Two main goals are achieved. For the first, the catalog allows the stress regime and kinematics characterizing the studied area to be depicted at a regional and more local scale. In particular, moving along the tectonic lineament that extends from the Aeolian Islands to the Ionian Sea, there is a change from a regime characterized by sub-horizontal P-axes, ca. NW-SE directed, to an extensive one in the Calabro-Peloritan Arc, where T-axes striking in a NW-SE direction prevail. Our results also show that part of the seismicity is clustered along the main active seismogenic structures, of which the focal mechanisms indicate the kinematics. Finally, in the Etna volcano area, different stress fields act at different depths due to the combination of the regional tectonics, the strong pressurization of the deep magmatic system, and the dynamics of the shallower portion of the volcano. As a second goal, we highlight that the catalog also represents a valuable tool, through the data distribution on the internet, for further studies directed towards improving our understanding of the geodynamic complexity of the region, and for a better characterization of the seismogenic sources.