bluuebunny/crossref_metadata_2025 huggingface dataset:
The separation of the geomagnetic field originated in the core, in the asthenosphere, and in the crust
Authors: G. P. Gregori  , W. J. Dong  , X. Q. Gao  , F. T. Gizzi
Published: June 2021

The separation of the field produced by different internal sources can be accomplished by means of the so-called spatial spectrum of the geomagnetic field of internal origin. It is shown how such a rationale, when suitably interpreted, allows to recognize the field that is originated by electric currents that flow either on the Inner-Core Boundary (ICB), or on the Core-Mantle Boundary (CMB), or on the Asthenosphere-Lithosphere Boundary (ALB). It appears crucial, however, to rely on satellite measurements alone, because ground-based and ship- and air-borne records are severely perturbed by the crustal field. Therefore, it is shown, on the basis of a critical reconsideration of a few key-papers in the literature, that the best approach is to avoid mixing together all kinds of measurements. Satellite data are best suited for recognizing the dynamo field, while ground-based, ship- and air-borne records, which are measured much closer to crustal sources, are best suited, after subtraction of the satellite-derived dynamo field, for inferring the geomagnetic anomalies that are to be associated with crustal sources alone.
Compilation of shipborne magnetic and gravity data images crustal structure of Prydz Bay (East Antarctica)
Authors: T. Ishihara  , G. L. Leitchenkov  , A. V. Golynsky  , S. Alyavdin  , P. E. O'Brien
Published: June 2021

A magnetic anomaly map and a free air anomaly map of Prydz Bay, of the adjacent slope and over the continental rise area (63°S-69.5°S, 69°E-81°E) were compiled using Russian, Australian, Japanese and other available data (more than 20 000 km in total length). Adjustment of different data sets was performed before gridding and making contour maps. Crossover differences of the magnetic data were significantly reduced by removing data segments with short-period time variations, by applying time variation corrections of Mawson Station to Australian and Japanese data, and by giving a constant bias to each trackline. Crossover differences of the gravity data were also substantially reduced by applying a constant bias to each cruise/leg. According to the compiled gravity data, in the western part of Prydz Bay the continent ocean boundary is inferred to be situated around the shelf edge at the seaward end of Prydz Channel, while it is in the continental rise in the eastern part. The gravity data also suggest the presence of sediments in the Prydz Bay basin reaching a thickness of about 8 km and overlying a "granitic" layer; the Moho beneath the basin is located at a depth of about 22 km. According to the magnetic data, highly-magnetized rocks occur at shallow depths northwest of the Prydz Bay basin and other parts of Prydz Bay.
Latest improvements for the echo sounding system of the Italian radar glaciological group and measurements in Antarctica
Authors: I. E. Tabacco  , C. Bianchi  , M. Chiappini  , A. Passerini  , A. Zirizzotti  , E. Zuccheretti
Published: June 2021

Radio echo sounding is an active remote-sensing method using electromagnetic wave penetration in a particular medium such as ice and permits the measurements of its thickness, the level of the bedrock and inhomogeneities i.e. of the internal layering of glaciers. The Italian Radar Glaciological Group has implemented technical improvements on the system operating during the 1995-1996 Antarctic expeditions, increasing the horizontal and the vertical resolution by means of a new acquisition ensemble. The new system was used during the Antarctic expedition in 1997-1998. The present paper presents the latest improvements of the radar acquisition system and radar profiles extracted from the 1995-1996 and the 1997-1998 Antarctic expeditions are presented.
Dynamical tools for the analysis of long term evolution of volcanic tremor at Stromboli
Authors: R. Carniel  , M. Di Cecca
Published: June 2021

Stromboli is characterized by persistent seismic activity, both in terms of tremor and of discrete events associated with moderate explosions defining the so-called "Strombolian activity". This kind of permanent activity suggests the probable existence of a dynamical system governing the volcano. The purpose of this paper is to extract information on the "Stromboli dynamical system" from the seismic recordings. The analysis is carried out using the theory of non-linear dynamical systems and the delayed coordinates phase-space reconstruction. Several methods are presented and discussed in order to analyze volcanic tremor data in this framework; finally the time evolution of the computed parameters, both in the long term and close in time to paroxysmal phases, is presented and discussed. Evidence for a strong deterministic component in the dynamics of the volcano is shown.
Spectrogram analysis of selected tremor signals using short-time Fourier transform and continuous wavelet transform
Authors: T. Bartosch  , D. Seidl
Published: June 2021

Among a variety of spectrogram methods Short-Time Fourier Transform (STFT) and Continuous Wavelet Transform (CWT) were selected to analyse transients in non-stationary tremor signals. Depending on the properties of the tremor signal a more suitable representation of the signal is gained by CWT. Three selected broadband tremor signals from the volcanos Mt. Stromboli, Mt. Semeru and Mt. Pinatubo were analyzed using both methods. The CWT can also be used to extend the definition of coherency into a time-varying coherency spectrogram. An example is given using array data from the volcano Mt. Stromboli.
Best-basis analysis of broadband tremor signals
Authors: T. Bartosch  , P. Steffen
Published: June 2021

Active volcanoes usually generate highly non-stationary broadband tremor signals. Short-time shock events with a frequency content of several decades are superimposed on a stationary narrow band continuous tremor. Tremor signals of this type can be observed in the near field of many active volcanoes. In this paper we will demonstrate the analysis of such signals using a specific tremor signal of Mt. Stromboli (Sicily). We used the Best-Basis Algorithm (BBA) in order to compute a spectrogram which is adapted to signal properties on highly different scales. It turns out that the BBA can reveal better fitting properties of the tremor in the time-frequency plane compared to standard methods like Short-Time Fourier Transformation (STFT). Moreover, this very effective algorithm can be used for real time monitoring in the time-frequency plane, for data compression or for de-noising of the tremor signals.
A comparison of f0F hmE model calculations with El Arenosillo digisonde observations. Seasonal variations
Authors: A. V. Mikhailov  , B. A. de la Morena  , G. Miro  , D. Marin
Published: June 2021

Seasonal variations of hmE and f0F2 are analyzed using El Arenosillo digisonde observations during solar minimum (1995-1996). Unlike some widely used empirical models daytime hmE show seasonal variations with winter hmE being higher than summer ones and seasonal differences increase with solar zenith angle. Model calculations enable us to reproduce the observed hmE seasonal variations but the calculated daytime f0E values are too low if conventional EUV fluxes and dissociative recombination rate constants are used. A reduction of a (NO+ ) by taking into account Te > Tn in the E-region as it follows from probe measurements seems to be a plausible solution. The E-region ion composition corresponding to rocket observations may be obtained in model calculations using an appropriate [NO] height distribution. Calculated summer concentrations of [NO] are by a factor of 3-4 larger than winter ones at the hmE-heights.
Displacement pattern of the Sinai area: first results from GPS
Authors: F. Riguzzi  , S. M. Mahmoud  , A. Tealeb
Published: June 2021

A network of 12 GPS stations, seven of them located on the Sinai peninsula, another four on the west shore of the Gulf of Suez and the last on the inner Gulf of Aqaba (ELAT, Israel) was analyzed twice, processing GPS data recorded in November 1997 and in May 1998. A rigorous statistical analysis based on the F (Fisher) test applied on the detected coordinate differences showed significant displacement at all the sites located on the Sinai peninsula with respect to the others. The planar displacements of the Sinai sites are of the order of 1.5 cm in the considered time span. The agreement exhibited by the Sinai displacements, both in magnitude and azimuth, taking into account the associated errors, provides evidence that the Sinai peninsula behaves like a rigid block or sub-plate with respect to the African plate. A raw estimate of its mean velocity gives about 3.0 cm/yr and 208° of azimuth. Although it is not possible to draw exhaustive conclusions on the geodynamics of the Suez and Sinai areas and the lack of GPS data on the Arabian peninsula makes the analysis incomplete, our results agree well with the left lateral motion of the Aqaba-Levant fault. Moreover, no evidence of extension is detected for the Gulf of Suez, but rather unexpectedly, a contraction component seems to be found by the present work.
Seismic hazard assessment in the Northern Andes (PILOTO Project)
Authors: C. Dimaté  , L. Drake  , H. Yepez  , L. Ocola  , H. Rendon  , G. Grünthal  , D. Giardini
Published: June 2021

Five Andean countries (Bolivia, Peru, Ecuador, Colombia, Venezuela) and four European countries (Italy, Spain, Holland, Germany) cooperated in the PILOTO program ("Test area for earthquake monitoring and seismic hazard assessment"), launched under GSHAP and sponsored by the European Union (Ct.94-0103) to produce a unified SHA for the Andean region. Activities included the integration of national earthquake catalogues and source zonings in common regional databases and joint technical workshops for the assessment of the regional hazard, expressed in terms of expected peak ground acceleration with 10% exceedance probability in 50 years.
Teleseismic P-residual study in the Italian region - inferences on large scale anisotropic structure of the subcrustal lithosphere
Authors: J. Plomerová  , V. Babuska  , R. Scarpa
Published: June 2021

Jeffreys-Bullen (absolute) and relative P-wave travel-time residuals were analyzed over Italy and its surrounding using P arrival times from the ISC bulletins supplemented by the data from local observatories. We analyzed the travel-time station corrections by two independent methods to obtain information on lateral variations of the velocity structure over the area and a view of possible upper mantle anisotropy. In the first method, the station corrections are computed as a constant and two cosine terms with appropriate phase shifts. Besides a static term, the second method allows us to study the relative residuals in dependence both on azimuths and incidence angles and thus to investigate their spatial variations and to map lateral variations of anisotropic structure of the subcrustal lithosphere. The high and low-velocity directions inferred from the spatial distribution of the relative residuals as well as the high- and low-velocity upper mantle heterogeneities reflect the geodynamic development of the region, governed by the collision between the African and Eurasian plates
The solar-cycle variation of M(3000)F2 and its correlation with that of f0F2
Authors: S. S. Kouris
Published: June 2021

Using hourly monthly-median measured values from nine long-standing ionospheric sounding stations with data sets extending over several decades, best-fit empirical relationships are established for M (3000)F2 with different solar and ionospheric indices representative of state of the solar cycle. The statistical analysis shows that there is no difference in the degree of correlation in using one index over another. Comparisons are also made with similar relationships for monthly median f0F2 determined from the corresponding measurement data sets and the degree of correlation between the two ionospheric parameters is established.
Paleogeographical reconstructions compatible with Earth dilatation
Authors: G. Scalera
Published: June 2021

The present research concerns the study of the possibility of an increase in the size of the Earthbecause of a still unknown process. After a previous recognition of the existence in the Pacific of shape conformities in a number of pairs of continental and oceanic boundaries (Scalera, 1991, 1993a), a search for compatibility of these results with independent data sets, paleomagnetic and geological and paleontological was undertaken. The conclusion is that the Earth's dilatation is compatible with the used data, while nothing can be affirmed with certainty about the dilatation process or its continuity or discontinuity through geological time. A tentative model of the evolution of the trench-arc-backarc systems has been provided, tuning it in agreement with a dilatational planet.
Some theoretical aspects of the two-level magnetovariational method
Authors: M. Vellante
Published: June 2021

We discuss some theoretical aspects of the two-level magnetovariational method for the determination of the underground electrical structure. The properties of two new apparent resistivity functions, respectively depending on gain and phase of the transfer function of the horizontal magnetic field variations between the Earth's surface and a given depth, are examined for two-layer Earth models. The effects of a finite wavelength of the source field are also investigated. It is shown that the measurement of the attenuation of the magnetic vertical component generated by an inhomogeneous source field can provide further information on the vertical distribution of the Earth's conductivity. In particular, it is shown that the measurement of the transfer function of both vertical and horizontal components between two levels can be used to estimate the average conductivity of the interlying medium.
Regional geomagnetic field modelling: the contribution of the Istituto Nazionale di Geofisica
Authors: A. De Santis  , M. Chiappini  , G. Dominici  , A. Meloni
Published: June 2021

Models of the geomagnetic field are mathematical expressions able to represent the Earth's magnetic field space and time variations. Time variations on the long term basis are represented by the so-called secular variation. This paper describes and reviews recent activities of the Italian group at the Istituto Nazionale di Geofisica in regional magnetic field modelling. The models are introduced starting from the classical technique of Spherical Harmonic Analysis (SHA) undertaken for the first time by Gauss, the polynomial analysis and the regional harmonic analysis, specifically introduced as a regional analogue of SHA. In this last group the recent techniques of Spherical Cap Harmonic Analysis (SCHA), Translated Origin Spherical Cap Analysis (TOSCA) and Adjusted Spherical Cap Harmonic Analysis (ASHA) are also described and discussed.
Retrospective correlation
Authors: F. Mulargia
Published: June 2021

One of the main tools in phenomenological studies is the identification of correlations among different processes. This is essentially effected in retrospective with the specific aim of finding a positive result, and that leads to a parameter optimization which introduces a bias, so far only marginally considered, in the significance level of the results. If the correlation can be validated in a forward study in which parameters are kept fixed, such a bias is irrelevant. Unfortunately, forward studies are often infeasible for either cost or intrinsic reasons. This is the case of geophysics, due to the comparatively long time scale of recurrence of the phenomena. Unbiased estimates can be obtained in retrospective if each of the optimal choices is properly identified and accounted for. An estimate of the bias is made in a specific case, which can be written in closed form. While simulation confirms its good performance, the latter shows that apparently highly significant retrospective correlations may be insignificant.
A MT 2D modelling of the Apenninic margin and Bradanic trough after identification of an artificial e.m. wide-band source on the natural MT data
Authors: V. Iliceto  , G. Santarato
Published: June 2021

In the frame of Italian research project «CROP», a magnetotelluric (MT) survey was carried out in Southern Italy, above the Apulian platform, with the aim to investigate its transition beneath the Apennine chain. The MT stations were divided into two areas, the first around Lavello town, the second south of Mount Vulture inactive volcano. The standard processing of MT raw data, collected with the single-site scheme, gave fairly non-plane wave response as concerns data of Lavello area, while the volcano's area data were compatible with a natural plane-wave e.m. field response. The Lavello area results were shown to be heavily affected by a near field effect of a strong wide-band electromagnetic source located several kilometers NE of Lavello. After the identification of this effect and an attempt to interpret these data, a 2D interpretation of the whole survey was then possible and the main result can be summarized as follows: a) the «electrical» boundary of the Bradanic trough should be displaced about 4 km toward SW; b) in the area south of Melfi town, the carbonatic platform should lie at a depth of about 8 km.
Analysis of short time-space range seismicity patterns in Italy
Authors: F. Di Luccio  , R. Console  , M. Imotof  , M. Murru
Published: June 2021

In our paper we analyze the data base obtained from the observations of the Italian Seismological Network from 1975 to 1994 by using a simple algotithm to determine the rate of occurrence of seismic events condi- tioned by the occurrence of previous events after a period of quiescence. The number of observed pairs of earthquakes depends on several parameters: the magnitude threshold of the two events, the spatial and tempo- ral ranges of the quiescence period preceding the first (non aftershock) event, the time elapsed between the first and the second events and the spatial dimension of the alarm area. The Akaike information criterion was adopted to assess the optimal set of space-time parameters used in the definition of non-aftershock (events not related to a stronger previous one). In Central Italy, the rate of M ³3.8 earthquakes preceded by at least one M ~ 3.3 foreshock within 14.1 km and 2 days is 30%, while the rate of M ~ 3.3 earthquakes followed by a M ~ 3.8 mainshock in the same space time range is 7%. We observed that the probability that an earthquake of magnitude MI will be followed by an earthquake of magnitude M2 (success rate) fits the law log À = a+b (Mi -M2) with b approximately equal to l. By computing the success rate for given values of magnitude threshold of the first and the second events over a dense grid of spatial coordinates, we obtained maps of this feature over the investigated area. The results of this process document variations larger than a factor of five in the success rate over the Italian territory.
Finite element modelling of the recent- present deformation patter in the Calabrian arc and surrounding regions
Authors: D. Albarello  , E. Mantovani  , M. Viti
Published: June 2021

An attempt is made to quantify the implications of the hypothesis that the recent-present deformation pattem in the Calabrian arc and the adjacent African margin is mainly determined by horizontal tectonic forces in- duced by the relative convergence of the confining blocks (Africa and Adriatic)- Modelling of present-day tec- tonic processes is carried out by means of a 2D finite element scheme involving elastic shells in a piane stl-ess approximation- On the assumption that tectonic processes are strongly influenced by the presencc of major di,- continuitie", the model includes zones whcre most deformations can concentl-ate Convcrgent and divcrgcnt boundaries are simulated by narrow belts having elastic parameters lower than those in the surrounding regions, transform boundaries are reproduced by orthotl-opic elements, Kinematic boundary conditions are im- po,ed to simulatc the relative convergence between Africa and the Adriatic, Numerical experimcnts show that this convergence causes the lateral escape of crustal wedgcs in the Calabrian arc and the adjacent African mar- gin (Sjcily). The resulting microplate kinematics can account for the complex distribution of compressional, tensional and transcurrent deformations actually observed.
The earthquake of 1 January 1837 in Southern Lebanon and N orthern Israel
Authors: N. N. Ambraseys
Published: June 2021

All of our 20th-century information for the Levant Fracture and Dead Sea transform fault systems is for a qui- escent period in the seismicity. This is apparent when we consider earlier events which show that infi.equent earthquakes have occurred in the past along this system, an important consideration for the assessment of haz- ard and tectonics of the Middle East. One of these events was the earthquake of 1837 which caused heavy damage in Northem Israel and Southem Lebanon. This earthquake was a much larger event than earthquake catalogues indicate. We reckon it was a shallow, probably multiple event of magnitude greater than 7.0.
Is plate tectonis withstanding the test of time?
Authors: O. Shields
Published: June 2021

Since the theory of plate tectonics was first proposed thirty years ago, some problems have arisen in its practical application. These call into question its fundamental assumptions of horizontal plate motion, hotspot fixity, true polar wander, Panthalassa, and the Earths constant size while leaving seafloor spreading and subduction intact. A rapidity expanding earth solves these problems and privides an alternative viewpoint worth reconsidering.
Foreland deformation in the Central Adriatic and its bearing on the evolution of the Northern Apennines
Authors: A. Argnani  , F. Frugoni
Published: June 2021

Seismic profiles in the Central Adriatic show the presence of a WNW-ESE trending belt (Central Adriatic Deformation Belt, CADB) where broad folds of Quaternary age occur. Seismicity in the Adriatic foreland seems to be localised along the CADB which is interpreted as the result of foreland deformation linked to the Apennine fold-and-thrust belt and possibly due to the presence of an inherited structural discontinuity. Geological arguments indicate that the CADB lineament can continue underneath the Northern Apennines and might have affected its recent evolution, characterised by the rise of a linear orographic front.
The investigation of electromagnetic precursors to earthquakes in Armenia
Authors: S. Balassanian  , A. Mouradian  , A. Sahakian  , S. Kalinin  , M. Babayan  , A. Pogossian
Published: June 2021

The present work provides a sufficient theoretical substantiation of the anomalous distribution for Very-Low-Frequency (VLF) radio waves which is observed for all radio routes controlled by the National Survey for Seismic Protection (NSSP) of the Republic of Armenia. This event is connected with the ionosphere excitement over the strong seismic event preparation zone under the influence of intensively oscillated VLF electromagnetic waves falling on the ionosphere from the source called an area of uniformly oriented Zones of Separated Charges (ZSC) in the strong seismic preparation zone. ZSC, formed at the interfaces of solid, liquid, and gaseous phases of rocks, acquire identical orientation under the action of increasing elastic strain forces. These strain forces may cause the effect of mutual polarisation of ZSC in the field of their high concentration. As a result, in the strong earthquake preparation zone, the most sensitive to the deformation ZSC, non-linear electromagnetic effects may be observed. One of these effects is the irreversibility of non-stationary electromagnetic processes (INP). It is shown that the INP method developed by Balassanian and Kabilsky (Balassanian, 1990) may prove to be very sensitive to the deformations of geological medium in the earthquake preparation zone.
On the interpretation of large-scale seismic tomography images in the Aegean sea area
Authors: G. A. Papadopoulos
Published: June 2021

A review of the interpretations given to large-scale seismic tomography anomalies in the Aegean area indicates a strong contradiction between these interpretations and the traditional ones based on seismic and tectonic data: 1) the tomographic lithospheric slab penetrates down to at least 400 km which doubles the maximum depth of the Benioff zone seismicity; 2) the resulting minimum time estimates for the subduction process duration at least doubles the seismotectonically calculated maximum time of 13 Ma for the subduction initiation. An alternative interpretation is proposed: the tomography detects not only the South Aegean active Benioff zone but also large remnants of lithospheric material subducted in two phases beneath the Aegean during the Miocene. Given that the geometric features of the paleosubductions are compatible with the features of the tomographic anomalies, it is suggested that the latter represent cool, non-assimilated lithospheric remnants. Then, no contradiction any longer exists and both seismotectonic and tomographic data are well explained.
The correlation between geomagnetic field reversals, Hawaiian volcanism, and the motion of the Pacific plate
Authors: G. P. Gregori  , W. Dong
Published: June 2021

The correlation between geomagnetic field reversals and volcanism is investigated, according to the speculated consequence on volcanoes of the transient electric currents in the geodynamo, through Joule's heating, before and after every reversal event. We evaluate the temporal variation during the last ~ 70 Ma both of the magma emplacement rate Q(t) from the Hawaii hot spot, and of the speed v(t) of the Pacific plate, by means of the observed volumes of islands and seamounts along the Hawaii/Emperor Seamounts chain, and their respective radiometric datings. Results confirm expectations. A justification of the volcanic crises that lead to the generation of the large igneous provinces during the last ~ 250 Ma also emerged. We describe in detail the complex pattern of the timings of the different effects. Joule's power is generally responsible for ~ 75-80% of magmatism, and friction power only for ~ 20-25%; but, on some occasions almost ~ 100% is fuelled by friction alone. The visco-elastic coupling between lithosphere and asthenosphere results ~ 96% viscous, and ~ 4% elastic.
Normal and anomalous behaviour of electric, magnetic and seismoacoustic signals recorded in the Amare cave
Authors: F. Bella  , P. F. Biagi  , M. Caputo  , G. Della Monica  , A. Ermini  , W. Plastino  , V. Sgrigna
Published: June 2021

Since 1987 multichannel instrumentation has been recording electromagnetic and seismoacoustic emissions in the Amare cave (Gran Sasso í L'Aquila). Equipment detecting RMC (Principality of Monaco) longwave broadcasting (216 kHz) has been operating in the same place. Data collected during this period have pointed out two different phenomena called «quiet» and «perturbed» that characterize the normal behaviour of the cave. On 25 August 1992 an earthquake with M = 3.9 occurred in the Gran Sasso area and on 4 June 1993 an earthquake with M = 4.3 occurred in Umbria, 100 km to north of the Amare cave. Before these earthquakes, electromagnetic, seismoacoustic, and RMC data showed anomalies. Here we present the observed phenomenology and discuss the possibility that the anomalies can be considered precursors of the earthquakes.
Inverse problem for tripotential measures in the study of buried cavities
Authors: P. Cosentino  , D. Luzio  , R. Martorana
Published: June 2021

This paper presents a solution to the inverse electrical problem for the interpretation of apparent resistivity anomalies due to empty buried cavities of quasi-spherical shape when tripotential measures are carried out. The anomalies of the apparent resistivities ra,rb andrg,and the composed resistivitiesrmand rt were previously calculated for a sufficient class of spherical models of resistivity anomalies. Then, for the whole class of models, some functionals of spatial distribution of the apparent and composed resistivity were identified and analyzed. They represent the average characteristics of the anomalies and, depending in a simple way on the fundamental parameters of the sources of the anomalies (average diameter and depth), they allow reliable estimates to be determined. Among the studied functionals, those allowing the most stable and less biased estimates of the anomaly source parameters are identified by numerical simulations with random noise perturbed data. Finally the trend of standard deviation and bias of the estimates of the unknown parameters were analyzed by varying the source models and the set of functionals used for the inversion.
Development of an early-warning system for monitoring remote volcanoes
Authors: G. Poupinet  , G. Sauvage  , J. P. Cauzac
Published: June 2021

Many andesitic volcanoes are quiescent for long time periods: usually (but not always) an increase in seismic activity and in deformation precedes an eruption by a few months or a few days. A UNESCO panel has put forward the concept of an early warning system for monitoring dormant volcanoes in remote regions. Simple seismic or deformation measuring devices can in principle be built for monitoring remote volcanoes. These instruments are composed of two units: 1) a processor that measures the baseline «activity» of the volcano and decides when the activity increases above a certain threshold; 2) a transmitter for long distance communication. For slow parameters like tilt or extensometry, the signal can be transmitted every few minutes or hours. For seismology, signals include a large quantity of data and therefore they are usually not transmitted. The processing unit is not easy to design because a single seismic station can record noises that are very similar to «volcanic events». Average noise level on a given time interval, event detection counters and high amplitude ground motion counters are a simple (but not exhaustive) way to summarize seismic activity. The transmission of data from the field to a monitoring center is feasible by present and future satellite telemetry. We present our attempt to develop an early warning system for remote volcano monitoring with data transmission by satellite.
Neural networks and dynamical system techniques for volcanic tremor analysis
Authors: R. Carniel
Published: June 2021

A volcano can be seen as a dynamical system, the number of state variables being its dimension N. The state is usually confined on a manifold with a lower dimension f, manifold which is characteristic of a persistent «structural configuration». A change in this manifold may be a hint that something is happening to the dynamics of the volcano, possibly leading to a paroxysmal phase. In this work the original state space of the volcano dynamical system is substituted by a pseudo state space reconstructed by the method of time-delayed coordinates, with suitably chosen lag time and embedding dimension, from experimental time series of seismic activity, i.e. volcanic tremor recorded at Stromboli volcano. The monitoring is done by a neural network which first learns the dynamics of the persistent tremor and then tries to detect structural changes in its behaviour.
Structural settings of the carbonatic "basament" and its relationship with magma uprising in the gulf of Naples (Southern Italy)
Authors: N. Fusi
Published: June 2021

The carbonatic "basement" of the Gulf of Naples, a peri-tyrrhenian basin located on the western side of the Southern Apenninic chain, was studied in detail by means of seismic reflection profiles both on the mainland and in the sea. The carbonatic "basement" dips toward the north-west with an angle of 100 and is affected by brittle extensional tectonics. This structural setting is related to the extension of the Tyrrhenian Sea, which caused the development of horst and graben-like structure along the western margin of the Apennines. Some normal faults with a regional relevance were recognised: 1 ) a N 110° trending fault responsible for the sinking of the carbonic "basement" below Mount Somma-Vesuvius; 2) a N 1O° trending fault, along which five sub- marine volcanoes are aligned; 3) a N70° fault, which separates the Gulf of Naples from the Gulf of Salerno. The first two faults, arranged radially with respect to the shallow magmatic chamber of Phlegraean Fields, are interpreted as the main uprising route for magma in this area. The carbonatic "basement"cannot be recognized in seismic profiles in the Phlegraean area; a tectonic feature responsible for this is hypothesised.
Probable values of rise and fall off time of solar cycles 23,24, and 25
Authors: N. Ortiz de Adler  , A. G. Elias
Published: June 2021

From an analysis of the rise and fall off time of solar cycles 4 to 22, a recurrence tendency of 7 cycles is observed in the rise time and, apparently, of 9 cycles in the fall off time. The envelope of these times presents a decreasing amplitude of oscillation. According to this behaviour, the rise and fall length of future solar cycles until cycle 25 can be inferred qualitatively. These values are compared with those obtained with a multiple regression method showing a good agreement.
First palaeoseismological results from Greece
Authors: S. Pavlides
Published: June 2021

This is a brief account of our approach to trends in palaeoseismological research that are currently emerging in Greece, with the application of modern investigative methods practised world-wide in active tectonic zones. These techniques include fault stratigraphy in trenches, and dating recent fault reactivations in order to understand and distinguish palaeoseismic events along specific segments of active faults, named Gerakarou (Mygdonia Basin, Thessaloniki area), Palaeochori Fault (Kozani-Grevena, Western Macedonia), Souli (Petousi, Epirus), and Volos-Larissa (Thessaly plain). Four palaeoearthquakes were investigated on the Gerakarou fault segment, with a uniform slip rate and return period around 7000 years. In Western Macedonia "aseismic areas" the Servia-Palaeochori recently activated fault shows a -3500 year quiescence. Three coseismic events on the Souli Fault pre- and post-date to 26000 year deposits.
Review of progress in gathering, distributing and using satellite data for activities within COST 238 (PRIME)
Authors: I. Kutiev  , S. Stankov
Published: June 2021

Recent progress in using the satellite data for various PRIME purposes is briefly presented. The satellite data base is already in operation and contains data of local plasma and neutral atmosphere parameters taken from several ionospheric satellites. A method of tracing the locally measured parameters along the magnetic field lines down to hmF2 is developed using a theoretical F-region code. This method is applied to receive f0F2sat needed to test monthly median and instantaneous mapping methods. In order to reduce the uncertainties arising from the unknown photoionization and recombination rates, f0F2 is calibrated at one point on the satellite orbit with a Vertical Incident (VI) f0F2 and their ratio is then assumed constant along the whole satellite track over the PRIME area. The testing procedure for monthly median maps traces the measured plasma density down to a basic height of 400 km, where individual f0F2sat values are accumulated in every time/subarea bin within the given month, then their median is calibrated with the available medians from the VI ionosonde network. From all available satellite orbits over the PRIME area, 35 of them were found to pass over two VI ionosonde stations. The second station in these orbits was used to check the calculated f0F2sat with the measured VI f0F2. The standard deviation was found to be only 0.15 MHz.
Intensity assessment from documentary data. Criteria and procedures in the daily practice of seismologists
Authors: A. Moroni  , G. Monachesi  , D. Albarello
Published: June 2021

A major problem in assessing macroseismic intensity from historical records is the lack of a standardized procedure for processing documentary sources and supplying unequivocal intensity estimates. In fact, most macroseismic, scales do not include detailed descriptions of procedures for intensity assessment and many divergent interpretations of intensity values arc obtained by different operators. In order to disclose these problems an experiment was made in Italy in 1994, in the framework of GNDT "Seismicity" Working Group. A set of selected documents concerning origil1al descriptions of effects produced by earthquakes which had occurred in Italy from 15th to 20th century, was supplied to a number of independent researchers. Each of them was invited to assess on this basis the intensity values and to explain his intellectual path by describing it in detail. This documentation was finally collected and, during a meeting devoted to this topic, the researchers involved were invited to discuss their personal experiences. The discussion indicated that the discrepancies between the estimate obtained by the different authors from the same documentary source are, in many cases, greater than 1 degree. This implies that the effect of personal choices may play an important role in intensity assessment and makes intensity estimates performed by the different authors less comparable. At present no definitive conclusions about these problems can be drawn but the topics focused during the meeting may represent a useful basis for a wider discussion to define a standardized procedure for thc assessment of intensity from documentary data.
The earthquake of 27thFebrary 1768 in Lower Austria: repair costs and seismic intensity in Wr.Neustadt
Authors: R. Gutdeutsch  , C. Hammerl
Published: June 2021

During the Age of Enlightenment the importance of administration increased. It left its traces in the official inquiries after natural disasters. For financial and other reasons authorities found it important to record the dam- age done to buildings by earthquakes. This background reflects the official inquiries after the damaging earthquake of 27th February I 768 in Lower Austria, which includes an important additional piece of information: a record of the respective damage costs il1 floril1s per house in Wr. Neustadt. In this study an attempt of quantification is made to relate the damage costs to the respective damage class and intensity according to the EMS- 92 scale. The earthquake intensity for Wr. Neustadt as a whole is estimated to be I = VII EMS-92. This result contrasts with older publications, where the intensity VII- VIII or VIII has been assessed.
Two strong historicaI earthquakes in Transylvania (Romania): November 19, 1523 and October 3, 1880
Authors: C. Radu  , E. Toro
Published: June 2021

The investigation into the historical seismicity of Romania evidences the occurrence of two strong earthquakes in Transylvania (central part of Romania) near the localities of Medias (1523) and Tàrnaveni (1880). Historical information on the 1523 earthquake, though poor, shows that it was felt on Saint Elizabeth's Day, which is celebrated on November 19, not on June 19 as proposed by previous studies and catalogues. Historical information on the 1880 earthquake allows a detailed study. The investigation concentrated on time, epicentral location and intensity distribution. The new macroseismic map shows a large area of I = VII (r7 = 20.7 km), the centre of which is proposed as the epicentral location, different from the previous ones.
Exploring the potentiaI of seismologicaI compilations: J. Schorn (1902) and the seismicity of Tyrol
Authors: P. Albini  , D. Bellettati  , M. Stucchi  , A. Zerga
Published: June 2021

Seismological compilations of the past two centuries have represented one of the main sources of supporting data for the compilers of current parametric earthquake catalogues, On the one hand, their quality and reliability was proved as varied and, in many cases, fairly low; on the other hand, it is not clear whether all the earthquake records they supply have been exploited to become part of the present knowledge of the historical seismicity of some European countries. This paper analyses one of these compilations, Die Erdbeben von Tirol und Vorarlberg, published in 1902 by J. Schorn, which covers an area today shared among Austria, Switzerland and Italy, with the aim of checking its reliability and its usefulness towards a revision of the knowledge on the seismicity of historical "Tyrol".
Problems of reliability in earthquake parameters determination from historicaI records
Authors: V. Castelli  , G. Monachesi
Published: June 2021

Earthquake parameters determination from macroseismic data is a procedure, the reliability of whose results can be impaired by many problems related to quality, number and distribution of data. Such problems are common with ancient, sketchily documented events, but can affect even comparatively recent earthquakes. This paper presents some cases of Central Italy earthquakes, the determination of whose epicentral parameters involved problems of reliability. Not all problems can ever be completely solved. It is therefore necessary to devise ways for putting on record the uncertainty of the resulting parameters, so that future users can be aware of them.
Parameters estimation of intensity decay relationships
Authors: F. Cella  , G. Zonno  , F. Meroni
Published: June 2021

This paper presents a methodology that analyses a set of observed intensities and estimates the parameters of an adopted attenuation law directly using the data points. A procedure was developed to define and evaluate the equivalent radii Di of the isoseismal lines. From these data it is possible to derive the parameters of the attenuation law. Moreover a validation procedure was developed to measure the capability of intensity decay relationships to reproduce the observed intensities. A case study of 55 earthquakes, divided into 9 subsets, of similar-attenuation zones, was analysed, using, as attenuation law, the one proposed by Grandori (1987, l991) to estimate either the parameters for each single earthquake or the parameters of an average intensity decay relationship for the similar-attenuation zones. The calculated intensity decay relationships result in 60- 70% of correctly reproduced points for most intensity data maps analysed. Analysing the similar-attenuation zones and different earthquakes simultaneously, the parameters of attenuation laws obtain results with a lower percentage of correctly reproduced points. The proposed methodology seems to be effective and suitable to reach practical results in parameters estimation of intensity decay relationships.
The June 12, 1995 microearthquake sequence in the city of Rome 1167
Authors: A. Basili  , L. Cantore  , M. Cocco  , A. Frepoli  , L. Margheriti  , C. Nostro  , G. Selvaggi
Published: June 2021

The earthquake of June 12, 1995 has been located using local and regional data (41°48.8'N, 12°30.8°6E at a depth of about 11.5 km) a few kilometers inside the city limit of Rome, in its southernmost part. This is the first event that occurred in Rome for which instrumental data are available. The local magnitude estimated from digital recordings is ML 3.6 and it was largely felt reaching intensity VI MCS. We constrained the focal mechanism by analyzing the S-wave polarization and it agrees well with the distribution of P-wave polarities. The fault plane solution shows a dominant strike slip mechanism (strike 275°, dip 70°, rake - 140°). Seismic moment, M0 = 2.3 ± 0.6 1021dyne × , was computed from S-wave displacement spectra of horizontal components of ground motion digital waveforms. The corresponding source radius ranges between 200 and 500 m, depending on the assumed stress drop (100 bars or 10 bars, respectively). The earthquake was preceded by a ML 2.6 foreshock. The seismic sequence lasted a few days during which 38 aftershocks were recorded. The seismicity pattern shows the characteristics of a mainshock-aftershock sequence, rather than swarm behavior which seems to characterize the activity of the neighboring seismogenic areas of the Alban Hills. We used a master event algorithm to locate some of the aftershocks. Results show that the relocated aftershocks are clustered in a small volume in proximity of the mainshock hypocenter.
Spanish sources concerning the 1693 earthquake in Sicily
Authors: F. Rodriguez de la Torre
Published: June 2021

When the great 1693 earthquake occurred, Sicily was a viceroyalty of Spain. In order to find primary and direct sources, the Archivo General de Simancas has to be investigated. Due to the lack of extensive and adequate catalogues it is difficult search amongst the millions of documents filed there. The author located among numerous bundles of papers of different Sections. a total of 238 manuscripts (with 850 pages) and 4 printed edicts related to the 1693 earthquake. All the gathered information offers good prospects of true knowledge on many aspects related to the seismic catastrophe: perception area. number of victims, ruin of towns, list of aftershocks. reconstruction. health and public order problems, and all those problems that surround a great historic earthquake (economic, political, social and religious).
Some aspects of historical research on <> earthquakes in eighteenth century Europe
Authors: P. Albini  , N. N. Ambraseys  , J. Vogt
Published: June 2021

In the framework of the CEC project <<Review of Historical Seismicity in Europe (RHISE),,. the investigation of transfrontier earthquakes has been one of our main tasks. Using a number of case histories, among many others considered during the project, some of the specific problems encountered during the research <> the border areas and <> repositories are presented, with special attention paid to eighteenth century Europe.
Seismic damage and destructive potential of seismic events
Authors: D. Abruzzese  , S. M. Petrazzuoli
Published: June 2021

This paper has been written within a research framework investigating the destructive potential of seismic events. The elastic response spectra seem insufficient to explain the behaviour of structures subject to large earthquakes in which they experience extensive plastic deformations. Recent works emphasise that there were many difficulties in the definition of a single pararneter linked to the destl-uctive potential of an earthquake. In this work a study on the effect of frequency content on structural damage has been carried out. The behaviour of two different elastoplastic oscillators has been analysed, considering several artificial earthquakes. The results obtained suggest a method for evaluating the destructive seismic potential of an earthquake through the response spectra ad the frequency content of the signal. and through the mechai~ical characteristics of the structures within the analysed area.