bluuebunny/crossref_metadata_2025 huggingface dataset:
The active Nea Anchialos Fault System (Central Greece): comparison of geological, morphotectonic, archaeological and seismological data
Authors: R. Caputo
Published: June 2021

The Nea Anchialos Fault System has been studied integrating geological, morphological, structural, archaeological and seismic data. This fault system forms the northern boundary of the Almyros Basin which is one of the Neogene-Quaternary tectonic basins of Thessaly. Specific structural and geomorphological mapping were carried out and fault-slip data analysis allowed the Late Quaternary palaeo-stress field to be estimated. The resulting N-S trending purely extensional regime is consistent with the direction of the T-axes computed from the focal mechanisms of the summer 1980, Volos seismic sequence and the April 30, 1985 Almyros earthquake. A minor set of structural data indicates a WNW-ESE extension which has been interpreted as due to a local and second order stress field occurring during the N-S regional extension. Furthermore, new archaeological data, discovered by the author, have improved morphology and tectonics of the area also allowing a tentative estimate of the historic (III-IV century AD. to Present) fault slip rate. Several topographic profiles across the major E- W topographic escarpment as well as along the streams, have emphasised scarps and knick-points, further supporting the occurrence of very recent morphogenic activity. In the last section, the structural, morphological and archaeological data are compared with the already existing seismological data and their integrated analysis indicates that the Nea Anchialos Fault System has been active since Lower(?)-Middle Pleistocene.
Holocene uplift and palaeoseismicity on the Eliki Fault, Western Gulf of Corinth, Greece
Authors: I. Stewart
Published: June 2021

Radiocarbon dating of elevated coastal phenomena along the emergent footwall of the Eliki Fault in the West- em Gulf of Corinth has established a chronology of tectonic emergence during Holocene times. The results confirm -6 m of coastal uplift over the last 3000 years at sites both immediately adjacent to, and more distant from, the offshore l'ault. Although revealing little or no spatial vm.iation along the fault, temporally the data de- fine two phases of enhanced tectonic activity (0-3000 year B.P. and pre- 7-8000 year B.P.) separated by a 4- 5000 year period of tectonic quiescence. Well documented historical surface faulting during the most recent lclive phase testify to the contribution to net uplift played by coseismic increments, but these are considered to be superimposed on significant aseismic movements. While asesismic uplift confuses the palaeoseismic .ecord, correlation of prominent notch levels with dated raised shoreline fauna provides evidence for at least 3 surface faulting events during the past 2500 years.
Geomorphic and archaeological -historical evidence for past ealihquakes in Greece
Authors: K. Gaki-Papanastassiou  , D. Papanastassiou  , H. Maroukian
Published: June 2021

Geomorphic observations focused on landforms of marine and fluvial origin such as notches, beachrocks, stream channel shifts, alluvial terraces and knickpoints, when combined with historical and archaeological information are able to date seismic events that took place in the past in some places of the Peloponnesus. At thc Eastern Gulf of Corinth, a seismically active area, all the geomorphic observations fit quite well with the deformation field induced by the action of an offshore fault. At Mycenae, a seismically inactive area with no historical evidence of earthquakes, the archaeological information is the only evidence for past earthquakes while geomorphic data indicate the most probable activated fault. At Sparta, an area of low seismicity but with historical evidence of destructive earthquakes, the geomorphic evidence helps to identify the most likely ruptured fault. At Eliki, a seismically active area with well documented historical activity, the geomorphic data serve to define the causative fault.This paper shows that although historical and archaeological data provide evidence far the occurrence of past earthquakes and often their date, geomorphic observations must be used to identify the causative fault.
Evidence for past earthquakes in an area of low historical seismicity: the Catalan coastal ranges, NE Spain
Authors: E. Masana
Published: June 2021

The Catalan coastal ranges are situated far away from a plate margin and thus are characterised by low rates of deformation and low seismicity. Nevertheless, up to six morphological scarps in quaternary alluvial fans, large landslides and liquefaction features were detected in the southern half of these ranges and motivated a more detailed geomorphologic and palaeoseismologic study. In the Baix Ebre Fault zone, the morphological analysis of the mountain front and the fluvial network showed evidence of alternative periods of uplift and quiescence and suggested a sub-actual reactivation of the fault after a recent stable period. In El Camp zone the Almadrava andMont-roig scarps were analysed in detail. The first shows evidence of fault control and of two probably seismic deformation events. A normal semi-hidden fault that folds the surface was suggested to explain the deformation observed in this scarp. The second is also considered to be controlled by a fault which was active between 100000 and 4490-4790 year B.C. If creep deformation could be rejected the Mont-roig scarp fault may be considered an active fault able to generate large earthquakes (M > 6.5). In summary, although the zone shows low historical seismicity, evidence that can be referred to past earthquakes was detected. Further palaeoseismologic studies should be carried out in these structures in order to better constrain the active behaviour of the faults.
Quasi-five- and ten-day oscillations in f0F2 and their possible connection with oscillations at lower ionospheric heights
Authors: D. Altadill  , J. Lastovicka
Published: June 2021

The statistical analysis of the 5-day and 10-day oscillations inferred in the upper and lower ionosphere in Central Europe from f0F2 measured in Pruhonice and the radio wave absorption in the lower ionosphere shows a remarkable degree of similarity for relative amplitudes of oscillations (not for absolute amplitudes). The relative amplitudes in both regions do not express a significant solar cycle effect and their seasonal variation is also similar except for winter. The typical relative amplitude of both 5- and 10-day oscillations in the F2-region is about 4%, which is useful information for PRIME.
HF radio emissions as a tool of ionospheric plasma diagnostics
Authors: H. Rothkaehl  , Z. Klos
Published: June 2021

The electromagnetic emission in the topside ionosphere has been investigated since the first satellites were located on the orbits. HF measurements can be used to diagnose the different electron plasma waves as well as the typical ionospheric parameters like f0F2. This paper presents the examples of measurements of the ionospheric RF radio noises in 0.1-10.0 MHz frequency range, which have been observed on the boards of the Intercosmos-19, Intercosmos-24, APEX satellites in the period 1979-1992, and the current experiment CORONAS.
The mean solar magnetic field as an indicator of the interplanetary magnetic field
Authors: J. Bremer
Published: June 2021

The Mean Solar Magnetic Field (MSMF) measured daily by ground based observations at the Standford Observatory shows similar structures like the Interplanetary Magnetic Field (IMF) near the Earth about 5 to 7 days later. The ionospheric effect in the mid-latitude F2-region due to such MSMF changes is most marked for strong MSMF changes from anti to pro sectors. The mean ionospheric response is very similar to the results obtained earlier with IMF sector structure data derived from Svalgaard (1976) and Wilcox (1982, private communication). Therefore, the MSMF data can successfully be used to predict the mean IMF sector structure and the mean ionospheric response 5 to 7 days in advance.
Solar cycle effect on oscillations in the period range of 2-20 days in the F region of the ionosphere
Authors: J. Lastovicka  , P. Mlch
Published: June 2021

The results of Lastovicka and Mlch (1994) and Altadill and Lastovicka (1996) are extended by the use of f0F2 and h'F data from Juliusruh, Lannion and Rome. There is a strong solar cycle effect in amplitudes of oscillations in f0F2 but none or a weak solar cycle effect in relative amplitudes of oscillations in f0F2 and in amplitudes of oscillations in h'F. The conditions when the planetary wave type oscillations should be taken into account in short-term predictions and when, on the other hand, they need not be taken into account, are partly specified.
A single-station spectral model of the monthly median F-region critical frequency
Authors: D. V. Pancheva  , P. Y. Mukhtarov
Published: June 2021

A new single-station monthly median model of the F-region critical frequency has been obtained. A goniometric functional approximation of the monthly median hourly values of f0F2 was accepted. The diurnal course of f0F2 was described by a constant component and four "tides". Only the influence of the annual and semiannual waves in the seasonal course of f0F2 was taken into account. The solar activity was depicted not only by the well known R12 - index, but also by the parameter KR, expressing the linear trend of the monthly mean values of the sunspots for the previous 12 months. The use of this new parameter gives an opportunity for the solar cycle investigated not to be divided into falling and rising parts. The main advantage of the presented monthly median spectral model is that the same approach could be used for the short-term prediction.
Large seismic faults in the Hellenic arc
Authors: B. S. Papazachos
Published: June 2021

Using information concerning reliable fault plane solutions, spatial distribution of strong earthquakes (Ms³ 6.0) as well as sea bottom and coastal topography, properties of the seismic faults (orientation, dimension, type of faulting) were determined in seven shallow (h < 40 km) seismogenic regions along the convex part of thc Hellenic arc (Hellenic trench) and in four seismogenic regions of intermediate depth earthquakes (h = 40-100 km) along the concave part of this arc. Except for the northwesternmost part of the Hellenic trench, where the strike-slip Cephalonia transform fault dominates, all other faults along this trench are low angle thrust faults. III thc western part of the trench (Zante-west Crete) faults strike NW-SE and dip NE, while in its eastern part (east Crete-Rhodos) faults strike WNW-ESE and dip NNE. Such system of faulting can be attributed to an overthrust of the Aegean lithosphere on the eastern Mediterranean lithosphere. The longest of these faults (L = 300 km) is that which produced the largest known shallow earthquake in the Mediterranean area (21 July 365, Ms = 8.3) which is located near the southwestern coast of Crete. The second longest such fault (L = l 70 km) is that which produced a large earthquake (December 1303, Ms = 8.0) in the easternmost part of the trench (east of Rhodos island). Both earthquakes were associated with gigantic tsunamis which caused extensive damage in the coast of many Eastern Mediterranean countries. Seismic faults of the intermediate depth earthquakes in the shallow part of the Benioff zone (h = 40- 100 km) are of strike-slip type, with a thrust component. The orientations of these faults vary along the concave part of the arc in accordance with a subduction of remnants of all old lithospheric slab from the convex side (Mediterranean) to the concave side (Aegean) of thc Hellenic arc. The longest of these faults (L = 220 km) is that which produced the largest known intermediate depth earthquake in the whole Mediterranean area (12 October 1856, M = 8.2) north of Crete. The second longest such fault (L = 160 km) produced a large earthquake (26 June 1926, M = 8.0) in the easternmost part of the concave part of the arc (near Rhodos). Both earthquakes caused very serious damage in several Eastern Mediterranean countries but were not associated with tsunamis.
Modern rheology and electric induction: multivalued index of refraction, splitting of eigenvalues and fatigue
Authors: M. Caputo
Published: June 2021

The modern constitutive equations of the rheology of analeptic media and of the polarization in dielectric media are discussed in the time and frequency domains. It is seen that the most appropriate form of the constitutive equations of these media is based on the convolution of the stress and strain, and of the electric field and induction respectively, with appropriate functions representing the memory of the medium to previous stress or induction. The most successful memory forma]ism in representing the observed phenomena is that of the derivative of fractional order which allows a variety of problems to be solved by means of the Laplace Trans- form. The consequent index of refraction, generally, is a set valued function which implies that a monochromatic wave generated in the medium is split into a set of waves with the same frequency but different wavelength which interfere and have a quasi periodically varying amplitude. The eigenfunctions of these media, associated to the ordinarily used principal values of the index of retraction, are split and so are the tree modes. The fatigue of anelastic media is studied using the new constitutive equations containing fractional derivatives; a phenomenological method is introduced to compute the number of cycles which gives fatigue for a strain or stress with given amplitude and frequency. The number of cycles which may cause fatigue is proportional to the amplitude and frequency of the applied strain or stress, or inversely proportional to the rate of stress or strain. A criterion is also established to see whether an applied cyclic stress or strain may cause fatigue. This criterion is tested with experimental data on steel and rocks verifying that, in general, it is consistent with the data although thc data are not always in the linear range. It is tentatively seen that fatigue docs not seem one of the causes of the release of the elastic energy stored in the Earth.
Modelling the light-ion densities in the ionosphere
Authors: S. M. Stankov
Published: June 2021

A steady-state theoretical model is used to obtain variations of the H+/O+ and He+/O+ density ratios in the upper ionosphere at middle latitudes. The model results are compared with the existing data from satellite measurements. Analytical functions are constructed approximating the latitude and altitude variations of these ratios.
Assessment of the solar-cycle dependence of f0F2 1157
Authors: T. D. Xenos  , S. S. Kouris  , B. Zolesi
Published: June 2021

Comparisons between observed hourly monthly-median values of f0F2 at Slough and Rome, and calculated f0F2 values using as an index of solar activity R12 or T12, demonstrate that there is practically no difference in the results when a solar (e.g., R12) or ionospheric index (e.g., T12) is used. The choice of the index should be based on other criteria. It is also shown that there is a slight degree of favourability for a quadratic law between f0F2 and each index of solar activity. Therefore, in mapping F-layer characteristics a second-degree relation should be adopted independently of rising or falling solar-cycle. Saturation and hysteresis effects could be then minimised.
Austral electrojet indices derived for the great storm of March 1989 1177
Authors: V. M. Silbergleit  , M. M. Zossi de Artigas  , J. R. Manzano
Published: June 2021

Available magnetic records from eight stations in the Antarctica, for the March 1989 geomagnetic storm, are used to construct the southern hemisphere auroral indices, analogous to the boreal ones. The results show a diurnal variation depending on the distribution of the stations. An acceptable correlation between the northern and southern hemisphere indices are found except for the index indicating the presence of the eastward auroral electrojet. However, differences in the amplitudes of both auroral electrojet indices were observed.
Local seismicity in Rome (Italy): recent results from macroseismic evidences
Authors: A. Tertulliani  , P. Tosi  , V. De Rubeis
Published: June 2021

This paper presents the results obtained from the study of the macroseismic effects of the June 12, 1995 Rome earthquake. The event, MD = 3.8, provoked VI degree MCS effects in neighbourhoods of Southern Rome. This earthquake is important within the framework of seismicity in the Rome area, as it is the first noteworthy one ever to be recorded in the instrumental age, and provides a good comparison with historical earthquakes which have occurred in the same area. The filtering procedure performed on the macroseismic field reveals out the anomalies of the attenuation pattern and the site effect. The results reconfirm what has only recently emerged from the analysis of historical earthquakes, i.e. Rome is affected by local seismicity, that can cause damage in the southern neighbourhoods and the downtown area, especially where the site contributes to the amplification of the effects.
A perturbative solution of the power-law viscoelastic constitutive equation for lithospheric rocks
Authors: M. Dragoni  , T. Lenci  , S. Santini  , F. Vetrano
Published: June 2021

A power-law, viscoelastic constitutive equation for lithospheric rocks, is considered. The equation is a nonlinear generalization of the Maxwell constitutive equation, in which the viscous deformation depends on the n-th power of deviatoric stress, and describes a medium which is elastic with respect to normal stress, but relaxes deviatoric stress. Power-law exponents equal to 2 and 3, which are most often found in laboratory experiments, are considered. The equation is solved by a perturbative method for a viscoelastic layer subjected to a constant, extensional or compressional, strain rate and yields stress as a function of time, temperature and rock composition. The solution is applied to an ideal extensional boundary zone and shows that the base of the crustal seismogenic layer may be deeper than predicted by a linear rheology.
Damage pattern in historical centres: Isernia, an example in Southern Italy
Authors: E. Esposito  , L. Laurelli  , S. Porfido
Published: June 2021

As regards the July 26, 1805 earthquake, a detailed study on the damage suffered by the town of Isernia has been carried out. As a first step in our research, we analyzed a manuscript of the time, in which describes damage to public buildings, churches and some notable houses caused by the earthquake. In order to identify such damaged sites, several archival sources and documents from 1816 to 1955 have been examined, on account of the remarkable changes in toponymy which occurred after 1861 and caused by the 1943 bombing. Moreover, due to the lack of cartography of the time, a 1875 map or the town has been used and compared with the land registry maps of a later period. The analysis of the 1805 damage pattern shows that the historical centre of the Isernia town is divided into three areas whose damage level is fairly differem: such areas are respectively located in the southern, central and northern part of the town with an increase in damage from South to North.
The seismic history of Italy in the Hebrew sources
Authors: G. Busi
Published: June 2021

Over more than two thousands years the Italian Jews have produced an impressive quantity of documentary materials. To spot the data of the seismical events. therefore, has not been easy, and the results can still be supplemented, though the research has been carried out on a quite large and rich material both manuscript and printed in the Hebrew language. The crop was large and interesting, since documents about eleven different earthquakes in Italy have been found. They are texts of various kinds. sornetilnes just short notes, but very often long liturgical poems or whole writings. through which the Jewish minority traces its own historical memory and its own understanding of these exceptional tragic events. From the Middle Ages till the first half of the XIX century. Italian literature in the Hebrew language records the earthquakes of Ancona (1279), Norcia (1328). Ravenna (1468). Ferrara 11570). Lugo (1688), Ancona (1690), Mantua (1693), Leghorn (1742), Lugo (1781). Siena (1798) and Alessandria (1829). Naturally. in the towns that had a major Jewish community the data are richer and give more detailed inforn~ation:th is is the case, for instance, of the earthquake of Ferrara, in the second half of the fifteenth century. Here Azaryah de' Rossi gives us not only a vivid account of the reactions of his fellow Jews, but also the fullest and most organic essay on the causes and the meaning of the earthquakes. We also possess a remarkable abundance of Hebrew sources on the earthquake that struck Leghon~ in January 1742: among other very interesting documents. there is also a true daily diary, in which the strength and the nature of the shakes are recorded, during the quite long period the earthquake lasted, that is till the end of March of the same year.
Using 1 -D and 2-D modelling of ground motion for seismic zonation criteria: results for the city of Rome
Authors: A. Rovelli  , L. Malagnini  , A. Caserta  , F. Marra
Published: June 2021

The geological information collected in the last years by the Istituto Nazionale di Geofisica for the city of Rome is used to construct 1- and 2-D models of the nearsurface structure. These models are the basis for the numerical generation of synthetic accelerograms which can simulate the horizontal ground motion (SH waves) produced in the different areas of the city by a large (M ? 7) potential earthquake 100 km away in Central Apennines. The proposed methodology yields earthquake engineering parameters (peak ground acceleration and velocity, Arias intensity, energy flux, response spectra) whose spatial variations are consistent with the damage distribution caused by the strongest earthquakes felt in Rome during its long history. Based on the macroseismic inforination and the results of the numerical simulations, general criteria for seismic zonation of the city of Rome are proposed.
Parameters and criteria for repair and strengthening of buildings in the old town core of Dubrovnik based on seismic risk analysis
Authors: M. Vladimir
Published: June 2021

Definition of the seismicity conditions, the design seismic parameters and the seismic risk level are important and inevitable phases ol the complex process of repair and strengthening of existing structures in certain towns located in seismically active areas. These should be studied in all necessary details in order to provide corresponding bases and define the necessary preventive measures against expected strong earthquakes. Such an approach becomes even nlore necessary arter the experience regarding the last catastrophic earthquakes that occurred in Former Yugoslavia (Skopje. Banja Luka, Montenegro coast and Kopaonik) and inflicted heavy losses of human lives and material properties. The old town core of Dubrovnik is known for the large concentration of buildings of enorrnous cultural-historic importance. Considering the high seismic activity of this area. all these buildings are very likely to experience heavy damage and failure. Tlie history of the town records many catastrophic earthquakes that inflicted heavy material losses and loss of human lives. Here, we can rnention the great Dubrovnik earthquake of 1667 and the last Montenegro earthquake of April 15, 1979 with an epicenter in the Ulcinj-Bar area. The consequences of the latter are well known. The purpose of this paper is to present some results and experience gained from the investigations performed for the area of Dubro~nikil lustrated by several examples of buildings existing in the old town core of Dubrovnik.
The medieval earthquakes of the Armenian Plateau and the historic towns of Ayrarat and Shirak (Dvin, Ani, Erevan)
Authors: M. Hasrat'yan
Published: June 2021

The ancient Armenian capitals have been struck by particularly violent earthquakes throughout the ages. Their prestigious and original monuments have been destroyed and reconstructed many times. The author examines in particular the situation of the monumental complex of Dvin, which has been subjected to a thorough and extensive campaign of archaeological excavations over the last twenty years or so, and that of Garni. struck by a violent earthquake in the 17th century. It was during this quake that the ancient temple of Garni was ruined; it was completely reconstructed in the present century. The author notes that some architectural techniques adopted in Armenian churches may be interpreted as antiseismic measures. They were developed in an environment in which the frequent experience of seismic damage could have offered numerous empirical observations on which they could be based.
Ancient earthen constructions and antiseismic dwellings: Boni's project after the earthquake of 13th January 1915 (Avezzano, Italy)
Authors: E. M. Beranger
Published: June 2021

After the earthquake of 13th January 1915, the archaeologist Giacomo Boni (1859-1925), inspired by ancient building techniques. proposed the reconstruction of Marsica and the Middle Liri Valley with earthen dwellings. With the cooperation of the Italian Ministry of Agriculture, he organized an exhibition where he collected samples of vegetal trellises which were an essential support to implement these techniques. Furthermore, he rebuilt two huts on the Palatine (Orti Farnesiani): one rectangular, the other circular, inspired by terracotta urns which he himself had discovered a few years earlier exploring the famous ancient tombs in the Forum Romanum, near the temple of Antonino and Faustina, by the Via Sacra. Boni's unusual proposal was intended as an alternative to the plans put forward by seismic engineering which was developing in Italy at that time. This is a prime example of a clash between two different outlooks and cultures (humanism versus science) each of which claimed to offer solutions to attenuate the effect of earthquakes. We have so far been unable to establish whether any earthen dwellings were actually constructed in Marsica or the surroundings of Sora for the survivors of the earthquake of 13th January 1915. Unfortunately, only one of the many houses built with this technique. still existing in the Soran countryside can be dated (1924).
Seismic damage in historic town centres and attenuation criteria
Authors: A. Giuffrè
Published: June 2021

The structural significance of the damage scenarios characteristic of VIII and IX degrees on the MKS macroseismic scale is discussed with reference to the seismic behaviour of the buildings which make up the urban fabric of a historic town or city. In an VIII degree scenario, damage is limited to structurally precarious situations, while a IX degree scenario involves seismic damage to external walls. Mechanical interpretation of these scenarios provides the basis for intervention strategies sufficiently well defined as to constitute a guide for seismic damage prevention programmes. VIII degree damage is prevented by identifying precarious situations. while IX degree damage requires systematic action. A proposal is put forward for the clarification of seismic regulations and the usefulness of evaluating future earthquakes in macroseismic terms with reference to the safety requirements of new buildings is discussed.
Seismic damage and geological heterogeneity in Rome's Colosseum area: are they related?
Authors: R. Funiciello  , L. Lombardi  , F. Marra  , M. Parotto
Published: June 2021

According to the historical sources, the Colosseum suffered several types of damage related to earthquakes. In particular, the damage is mostly concentrated in the southern portion of the amphitheater where the study of the geological features shows the presence of a Holocene alluvial valley, a situation that is potentially responsible for significant amplification of ground motion during earthquakes. A detailed reconstruction of the subsurface geology in the area of the Colosseum was performed with the purpose of verifyipg whether the heterogeneity of the damage observed could be associated with the variability of the geological conditions of the site where the monument was built.
History, observation and mathematical models in the seismic analysis of the Valadier abutment area in the Colosseum
Authors: G. Croci  , D. D'Ayala  , R. Liburdi
Published: June 2021

The present work aimed to outline the need to investigate different fields of research to interpret the structural behaviour of a monument as complex as the Colosseum. It is shown how defining the numerical models first. then refining them, followed by interpretation of results. is strictly linked with the inforination gathered from historical records and observation of the ~nonumenta s it is today. The study is confined to the area of the Valadier abutment. analysing its state and its seismic behaviour before and after the XIX century restoration using different ilumerical tools, from the elastic modal analysis to the non linear step by step time history direct integration. The procedure comparati\ely evaluates the reliability in the interpretation of the results and identifies future lines or research.
Retrospective analysis of the Spitak earthquake
Authors: S. Y. Balassanian  , A. R. Arakelian  , S. N. Nazaretian  , A. S. Avanessian  , A. H. Martirossian  , V. A. Igoumnov  , M. G. Melkoumian  , A. V. Manoukian  , A. K. Tovmassian
Published: June 2021

Based on the retrospective analysis of numerous data and studies of the Spitak earthquake the present work at- tempts to shed light on different aspects of that catastrophic seismic event which occurred in Northern Arme- nia on December 7, 1988. The authors follow a chronological order of presentation, namely: changes in geo- sphere, atmosphere, biosphere during the preparation of the Spitak earthquake, foreshocks, main shock, after- shocks, focal mechanisms, historical seismicity; seismotectonic position of the source, strong motion records, site effects; the macroseismic effect, collapse of buildings and structures; rescue activities; earthquake conse- quences; and the lessons of the Spitak earthquake.
Tidal analysis of data recorded by a superconducting gravimeter
Authors: P. Baldi  , G. Casula  , S. Focardi  , F. Palmonari
Published: June 2021

A superconducting gravimeter was used to monitor the tidal signal for a period of five months. The instrument was placed in a site (Brasimone station, Italy) chat-acterized by a low noise level, and was calibrated with a precision of 0.2%. Then tidal analysis on hourly data was performed and the results presented in this paper; amplitudes, gravimetric factors, phase differences for the main tidal waves, M2, S2, N2, 01, Pl, K1, QI, were calculated together with barometric pressure admittance and long term instrumental drift.
Remarks on the mean-square values of the geomagnetic field and its components
Authors: A. De Santis  , C. Falcone  , F. J. Lowes
Published: June 2021

When considering functions on the Earth's (spherical) surface, mean-square values are often used to indicate their (relative) magnitude. If a function is separated into it, (essentially) spherical harmonic components then, provided these individual harmonic components are orthogonal over the surface, the concept of spatial power spectrum can be introduced, with each harmonic contributing separately to the total mean square value; this is true for the geomagnetic field vector B, its horizontal component vector H, and its vertical component z. However, because of the lack of orthogonality this concept is not applicable to the horizontal X and y components individually; problems which arise from this are discussed.
3-D crustal P-wave velocity tomography of the Italian region using local and regional seismicity data
Authors: B. Alessandrini  , L. Beranzoli  , F. M. Mele
Published: June 2021

A tomographic experiment was performed in the Italian region using local and regional arrivaI times of p and S seismological phases selected from the Italian National Bulletin in the time interval 1984-1991. We deter- mined a 3-D crustal P-wave velocity model using a simultaneous inversion method that iteratively re1ocates the hypocenters and computes the unknown model parameters. A fast two-point ray tracing algorithm was adopted to compute the ray paths and travel times of P", S", P g' Sg phases with good accuracy. Synthetic tests were performed using the "true" hypocenter and station distribution to rough1y evaluate the extension of the areas most densely spanned by the ray paths; the agreement between synthetic and computed models is more satisfactory at Moho depths than in the upper crust. The qua1ity of the model resulting from inversion of real data is examined by the ca1culation of the Spread Function (Toomey and Foulger, 1989). The 3-D crustal P-wave velocity mode1 of the Italian region shows remarkab1e trends at Moho depths: the areas east of the Apennines call for positive adjustments of the initial velocity va1ue, while the west region shows negative ad- justments. The correspondence among the main features of the velocity field, the map of Moho isobaths and the map of the gravity anoma1ies is also outlined.
Seismic effects of the strongest historical earthquak in the Syracuse area
Authors: E. Boschi  , E. Guidoboni  , D. Mariotti
Published: June 2021

The effects of earthquakes that occurred in a given area contribute significantly to the evaluation of to local seismic hazard. The information concerning historical earthquakes of the Mediterranean area covers many centuries, but the wealth of information made available by historical seismology does not appear to ha taken into account by engineering seismologists. By adopting "attenuation laws" based on data contained in the seismic catalogues, not only do we sometimes come up against the gross errors normally found jn logues, but we also lose sight of important details relating to the characteristics of urban seismic scenarios this paper we describe the results obtained from the analysis of seismic scenarios in Ortigia (old Syracuse this analysis we emphasized the qualitative and descriptive data to outline the "largest historical eve reassessed the data concerning five earthquakes that occuned in 1169,1542,1693,1757 and 1846, w reported by the Catalogue of Italian Earthquakes with an intensity greater than or equal to IX MCS epicentre of which was located within 50 km of the city. The last two of these earthquakes turned out t result of mistakes in the transmission of the news and have therefore been removed trom the list of de events. In addjtjon, we reconstructed the damage caused by the 1542 and 1693 earthquakes on a ma ancient town of Ortigia, taking into account the economic, demographic, and urbanistic conditions of t The empirical elements supplied to evaluate the local seismic response can also be of use in the preservation of historical buildings.
Amplitude response of a telemetered seismic system from seismometers to digital acquisition system
Authors: R. Di Giovambattista  , S. Barba  , A. Marchetti
Published: June 2021

Automated amplitude response of the complete seismometer, telemetry and recording system js obtaiued trom sinusoidal inputs to the calibration coil. Custom-built software was designed to perform fully automatic cali- bration analyses of the digital signals. In this paper we describe the signals used for calibration and interactive and batch procedures designed to obtain calibration functions in automatic mode. By using a steady-state method we reach a high degree of accuracy in the determination of both the frequency and amplitude of the \ignal. The only parameters required by this procedure are the seismometer mass, the calibration-coil constant and the intensity of the current injected into the calibration coil. This procedure is applicable to telemetered seismic systems and represents an optimization of the processing time. The software was designed to requjre no modification" jf the device used to generate the sinusoidal current should change. In particular, it is possi- ble to changc the number of monotrequcncy packages transmitted to the calibration coil with the on]y restric- tion that the difference between the frequency of two consecutjve packages be greater than 5%; for these rea- sons the procedure is expected to be usefu] for the seismological community. The paper inc]udes a generaI de- scription of thc designing criteria, and of the hardware and software architecture, as well as an account of thc system's performancc during a two year period of operation.
Rifting and thermal evolution of the Northwestern Mediterranean
Authors: V. Pasquale  , M. Verdoya  , P. Chiozzi
Published: June 2021

The structural setting of the Northwestern Mediterranean stems from tectonothermal processes which reflect on the nature of the crust. The Oligocene to Present evolution is here analysed with a thermal model which takes into account the significant extension of the continentallithosphere before the onset of sea-floor spread- ing in the bathyal zone. Subsidence data were used to set the boundaries of the oceanic realm which was com- pared with previous reconstructions inferred from other geophysical evidence. The thermal features of the transitional crust that lies between the oceanic crust and the stretched continental margins were also outlined. The Ligurian-Proven~al basin is a marginaI basin, whereas only the continental crust is expected in the Valen- cia trough. An evolutionary sketch of the study area that accounts for the observed subsidence and heat flux is proposed.
Positive and negative feedback in the earthquake cycIe: the role of pore fluids on states of criticality in the crust
Authors: I. G. Main  , P. G. Meredith  , J. R. Henderson  , P. R. Sammonds
Published: June 2021

Fluids exert a strong physical and chemical control on local processes of rock fracture and friction. For example they may accelerate fracture by stress corrosion reactions or the development of overpressure (a form of positive feedback), or retard fracture by time-dependent stress relaxation or dilatant hardening (negative feed-back), thereby introducing a variable degree of local force conservation into the process. In particular the valve action of dynamic faulting may be important in tuning the Earth to a metastable state of incipient failure on all scales over several cycles, similar to current models of Self-Organised Criticality (SOC) as a paradigm for eartiquakes However laboratory results suggest that ordered fluctuations about this state may occur in a single cycle due to non conservative processes involving fluids which have the potential to be recognised, at least in the short term, in the scaling properties of earthquake statistics. Here we describe a 2-D cellular automaton which uses local rules of positive and negative feedback to model the effect of fluids on failure in a heterogeneous medium in a single earthquake cycle. The model successfully predicts the observed fractal distribution of fractures, with a negative correlation between the predicted seismic b-value and the local crack extension force G. Such a negative correlation is found in laboratory tests involving (a) fluid-assisted crack growth in tension (b) water-saturated compressional deformation, and (c) in field results on an intermediate scale from hydraulic mining-induced seismicity all cases where G can be determined independently, and where the physical and chemical action of pore fluids is to varying degrees a controlled variable. For a finite local hardening mechanism (negative feedback), the model exhibits a systematic increase followed by a decrease in the seismic b-value as macroscopic failure is approached, similar to that found in water-saturated laboratory tests under controlled «undrained» conditions, and where dilatancy hardening is independently known to be a local mechanism of negative feedback. A similar pattern is suggested from selected field observations from natural seismicity, albeit with a lesser degree of statistical significance.
Artificial and natural electromagnetic signals revealed during two years in the Amare cave (Central Italy)
Authors: F. Bella  , R. Bella  , P. F. Biagi  , M. Caputo  , G. Della Monica  , A. Ermini  , W. Plastino  , V. Sgrigna
Published: June 2021

n 1990, some instrumentation was set up in the Amare cave (southern slope of the Gran Sasso chain, L'Aquila) in order to pick up electric signals ranging from 0.3 to 300 kHz, magnetic signals from 0.3 to 30 kHz and seismoacoustic signals by means of three geophones with natural frequencies of 0.3 kHz, 25 kHz and 150 kHz. Data are recorded every ten minutes on a solid state memory. The analysis of the data allows us to establish the existence of electromagnetic fields of distant origin connected with broadcastings and with tropical lightning activity and the discontinuous presence of local electric and magnetic signals, coupled with seismoacoustic ones, connected with weather events. A qualitative explanation of these near fields is given.
Self-potential time series analysis in a seismic area of the Southern Apennines: preliminary results
Authors: G. Di Bello  , V. Lapenna  , C. Satriano  , V. Tramutoli
Published: June 2021

The self-potential time series recorded during the period May 1991 - August 1992 by an automatic station, located in a seismic area of Southern Apennines, is analyzed. We deal with the spectral and the statistical features of the electrotellurie precursors: they can play a major role in the approach to seismic prediction. The time-dynamics of the experimental time series is investigated, the cyclic components and the time trends are removed. In particular we consider the influence of external noise, related to anthropic activities and meteoclimatic parameters, and pick out the anomalies from the residual series. Finally we show the preliminary results of the correlation between the anomalies in the time patterns of self-potential data and the earthquakes which occurred in the area.
Megasource time-domain electromagnetic sounding at Poggi del Sasso - Cinigiano (GR)
Authors: G. V. Keller  , P. Cantini  , R. Carrara  , O. Faggioni  , E. Pinna
Published: June 2021

An experiment was carried out in the vicinity of the I Terzi area in Southeastern Tuscany (fig. 1) to evaluate the applicability of the Time Domain Electromagnetic (TDEM) sounding method under the geological and environmental conditions prevailing in that area. An electromagnetic source was established using a motor-generator set and heavy cable. Measurements were attempted at four sites. Numerous samples of electromagnetic noise were recorded at each of these sites. At one site, signals transmitted for a grounded dipole source at 1.6 km distance were also recorded with the noise. The single set of observations has been processed and inverted to yield a six-layer piecewise constant resistivity depth-profile to a depth of about 2 km. The primary achievement of the experiment was demonstration of the praeticability of TDEM methods under the conditions prevailing in the site.
Experimental tests for characterization of GPR antenna patterns
Authors: E. Pettinelli  , N. Pierdicca  , S. Piro  , L. Versino
Published: June 2021

Detection and location of buried structures using the electromagnetic impulsive methodologies (GPR) require the study of the spatial distribution of energy irradiated by an antenna into the ground and the mechanisms of wave propagation and scattering from relevant targets. Evaluation of the difference in wave field distribution in the ground with respect to free space can provide some useful indications on the propagation of the Geo-radar signal in the ground and the spatial resolution capability of the GPR method. For this reason, a research group, involving La Sapienza University, Rome and the National Research Council began, during 1992, to perform studies on antenna radiation pattern, the propagation and scattering phenomena of GPR. This paper presents the experimental set up and the obtained results on the antenna radiation pattern.
A multidisciplinary approach for the study of the effects of active tectonics along the North Anatolian fault zone: possibilities for the application of the electrical self potential method
Authors: W. Balderer
Published: June 2021

The aims of this joint interdisciplinary project Marmara of ETH Zurich and the Istanbul Technical University (ITO) are to study the effects of active tectonics as evidenced by geology, geodesy and seismology on hydrogeology and geothermics in selected areas along the North Anatolian fault zone. Within the framework of this project thermal water systems in seven different areas have been investigated or are under investigation up to now (SchindIer et al., 1993). For three study areas along the North Anatolian fault zone (from east to west) of Kuzuluk/Adapazari, Bursa and of Canakkale the investigations with respect to the geological and hydrogeological features are complete. The now possible hydrogeological characterisation shows encouraging possibilities for the application of new methods like the electrical self potential method for the following reasons: 1) a fully interdisciplinary approach, including seismic survey with especially conceived network, geodetic survey to investigate tectonic movements by the GPS method, geothermic survey combined with geological mapping and hydrogeological investigations of normal mineral and thermal waters; 2) groundwaters of very different chemical and isotopical composition e.g.: Ca-HCO3-type thermal waters of up to 82 °C temperature and total mineralisation of 500 mg/I to 1500 mg/I in the Bursa area, Na-HCO3-type cold mineral waters of up to 2500 mg/I to thermal waters of same mineralisation of up to 80 °C temperature, containing large amounts of CO2 of up to 1 l per 1 kg of water (at surface conditions) in the Kuzuluk area and Na-Cl-type waters presenting real thermal brines of up to 65 000 mg/I of total mineralisation and temperatures of up to 100 °C in the Canakkale area; 3) distinct types of hydrodynamic flow regime in areas of different geological and tectonic structure. Based on the results of the investigations within these areas the possibilities of further studies including self potential methods are discussed.
A magnetovariational study in Central Italy: Standard techniques
Authors: E. Bozzo  , G. Caneva  , A. Elena  , M. Gambetta  , E. Zunino
Published: June 2021

magnetovariational study was performed in Central Italy, with an array of magnetometers located at Radicondoli (SI), Radda in Chianti (SI), Roccalbegna (GR), Città di Castello (PG) and Pennabilli (PS) from February to May 1992. Geomagnetic transfer functions in the frequency domain were calculated using the standard least squares tecnique. The induction arrows for the periods T= 32 min and T= 128 min, the Hypothetical Event (HE) maps and two IZ/HI pseudosections across the array, show the magnetovariational effect of the upper mantle anomaly in the Tuscan-Tyrrhenian area and the contrast between different crustal types.
Some events in Central Italy: are they all tsunamis? A revision for the Italian tsunami catalog
Authors: A. Maramai  , A. Tertulliani
Published: June 2021

he catalogs available in the literature show that tsunamis affecting Italian coasts are not very strong, except for a few well analyzed events, i.e. the Messina December 28, 1908 tsunami. This study aims at making a careful revision of some minor tsunamigenic events, in particular those occurred along the coasts of the Central Tyrrhenian Sea, considering tsunamis associated with earthquakes, from 1700 to 1919. These events have been poorly studied so far, and need a check to verify their reliability, even though they are reported in the catalogs. The results show how it is difficult to get a clear definition of those tsunamis, because of a gap in the historical sources, in spite of the large amount of seismological data concerning earthquakes related to the anaIyzed tsunamis. This analysis proposes to delete from the catalog some events for which a clear groundlessness appeared.