bluuebunny/crossref_metadata_2025 huggingface dataset:
Uniform regularity for the isentropic Hall-MHD system
Authors: Fan Jishan , Zhou Yong
Published: June 2021

In this manuscript, we consider the compressible Hall-MHD system, which is a mathematical model to describe magnetic reconnection in space plasmas, star formation, neutron stars, and geo-dynamics. In the system, there are two viscosity constants and a resistivity coefficient. Uniform regularity for the compressible isentropic Hall-MHD system is established in terms of these coefficients.
Development of a Self-reported Olfactory Dysfunction Questionnaire (SODQ) to screen olfactory disorders in China
Authors: Liu X. , Huang J. , Tian P. , Hu J. , Zou L.
Published: June 2021

Background: The diagnosis of olfactory dysfunction is challenging given the negligence during routine physical examination, inconvenience of diagnosis in clinical practice, and the inattention to cross-cultural adaptability. The study aimed to develop and validate a simple and effective self-reported olfactory dysfunction questionnaire (SODQ) for the initial screening of clinical olfactory disorders in China. Methods: A total of 121 subjects participated in the study; of these, 96 subjects completed the T&T olfactometer test and 12-item questionnaire, and 25 participants were retested using the SODQ after one week. The T&T olfactometer test examined the olfactory function and the questionnaire measured the ability to perceive common odors in daily life. We evaluated the factor structure, reliability, validity, and discriminative ability of the SODQ. Results: The final version of the SODQ consisted of 10 items with one factor. Test–retest and internal consistency were excellent. Convergent validity of the questionnaire with the T&T olfactory test was high. Furthermore, the discrimination ability was high for the questionnaire with an area under the curve of 0.95 and a cut-off point of 22. Conclusions: The SODQ is a brief, valid, and repeatable tool that has the potential to effectively screen for clinical olfactory disorders from a subjective perspective.
Coping with COVID: Developing a Rapid-cycle Frontline Quality-improvement Process to Support Employee Well-being and Drive Institutional Responsiveness in a Tertiary Care Faith-based Hospital in Rural Kenya
Authors: Adam Mary B. , Makobu Naomi Wambui , Kamiru Wilson Karuri , Mbugua Simon , Mailu Faith
Published: June 2021

The coronavirus disease 2019 (COVID-19) pandemic has demanded rapid institutional responses to meet the needs of patients and employees in the face of a serious new disease. To support the well-being of frontline staff, a series of debriefing sessions was used to drive a rapid-cycle quality-improvement process. The goals were to confidentially determine personal coping strategies used by staff, provide an opportunity for staff cross-learning, identify what staff needed most, and provide a real-time feedback loop for decision-makers to create rapid changes to support staff safety and coping. Data were collected via sticky notes on flip charts to protect confidentiality. Management reviewed the data daily. Institutional responses to problems identified during debrief sessions were tracked, visualized, addressed, and shared with staff. More than 10% of staff participated over a 2-week period. Feedback influenced institutional decisions to improve staff schedules, transportation, and COVID-19 training.
The impact of space weather on communication
Authors: Y. K. Tulunay  , P. A. Bradley
Published: June 2021

As a preliminary to the studies conducted by the individual Working Groups, a review has been undertaken of topics which are relevant to the space-weather phenomena that can occur. The ways in general that these can influence the state of the ionosphere are discussed. The various changes in propagation parameters that arise on Earth-space and terrestrial radio paths via the ionosphere are listed. International procedures for frequency allocation and assignment are explained and the extent to which these are influenced by propagation factors is addressed. The role of mitigation techniques to improve radio-system performance is also identified.
19th century earthquakes in Mexico: three cases, three comparative studies
Authors: A. Molina del Villar
Published: June 2021

This paper is a comparative study of the three strongest 19th century earthquakes in Mexico and their effects and impact mainly in Mexico City. The research is based on historical sources and previous investigations already published for two of the seismic events (8 March 1800 and 19 June 1858), with newly retrieved and analysed data for the 7 April 1845 earthquake. Primary and secondary sources include reports on damage to city buildings, streets and neighbourhoods and allowed a detailed analysis of the national and local effects, impacts and responses to each of the three earthquakes, whose comparison allows a better understanding of specific aspects related to the investigation of historical earthquakes in Mexico.
Seismic activity in Ghana: past, present and future
Authors: P. E. Amponsah
Published: June 2021

Though Ghana is far away from the major earthquake zones of the world, it is prone to earthquake disaster. Ghana has records of damaging earthquakes dating as far back as 1615. The last three major events occurred in 1862, 1906 and 1939. This paper presents the main historical and current instrumental recorded earthquakes of Ghana and the steps being taken to mitigate the negative effects of such disastrous occurrences in the country. The discussion is based on historical and current data obtained from the seismological observatories in Accra and Kukurantumi. Historical earthquakes of magnitude greater than 6.0 and current local tremors with magnitudes ranging from 1.0 to 4.8 on the Richter scale have been recorded since the establishment of the seismograph stations.
Catalogues of historical earthquakes in Italy
Authors: R. Camassi
Published: June 2021

A complete survey of historical earthquake investigation in Italy cannot be compressed into a few pages, since it would entail making a summary of widely different phases of research (performed by past scholars and by contemporary scientists and historians) and taking into account the widely different historical contexts, methodological assumptions and critical awareness of each of them. This short note only purposes to chart the main stages of the progress made by Italian historical seismology, from the late 17th century compilation by Bonito(1691) up to the latest parametric catalogue (Working Group CPTI, 1999).
State-of-the-art of historical earthquake investigation in Bulgaria
Authors: R. Glavcheva
Published: June 2021

This paper deals with non-instrumental seismology development in Bulgaria (the central-eastern part of the Balkan peninsula). The first steps and products of this scientific branch are discussed because they have traced the road of present-day historical seismology in this country. The sources of information on long-term seismicity are critically reviewed. Some recent studies, which contribute to an improvement of the supporting data sets, are also discussed. A special emphasis is laid on the rules adopted to solve different cases as well as on the aspects, by which our understanding of the seismogenesis throughout the present-day Bulgarian lands has been enhanced.
Implications of some early Jewish sources for estimates of earthquake hazardin the Holy Land
Authors: I. Karcz
Published: June 2021

For the past two millennia the Holy Land was under the yoke of successive invaders and oppressors, not a fertile ground for growth of historiographic traditions. Consequently, earthquake cataloguers had to rely largely on chronicles and texts written at distant administrative and cultural centers of the day, where earthquake destruction suffered by a culturally and economically depressed province may have been overshadowed by damage in more important parts of the empire. On this assumption, and aided by an implicit notion that the lands bounded by the Dead Sea Rift and Anatolian Fault systems are seismically contiguous, early cataloguers often extended the impact of earthquakes documented in nearby East Mediterranean countries to the Holy Land. Once published, such reports of supposed destructive intensities in Israel were used by Judaic scholars and archaeologists to date poorly defined, often metaphoric, literary seismic echoes, and to justify assigning seismic origin to equivocal signs of damage, asymmetry, or abandonment at archaeological sites of corresponding age. The spread of damage and intensity portraits are therefore enhanced and distorted, and so is their application in palaeoseismic analysis. Four test cases are presented, illustrating the use and misuse of local Judaic sources in identifying destructive intensities supposedly generated in the Holy Land by earthquakes of 92 B.C., 64 B.C. and 31 B.C., and in postulating a regional seismic catastrophe in 749 A.D..
Time intermittency and spectral features of the geomagnetic field
Authors: P. De Michelis  , G. Consolini
Published: June 2021

In the field of geomagnetism a number of studies have been devoted to the investigation of turbulence and intermittency in the outer core fluid motions. Here, in order to obtain information on such phenomena we study the time spectral and self-similarity features of the main geomagnetic field fluctuations as measured on the Earths surface. The existence of a power law spectrum, characterised by an exponent a-11/3, and an anomalous scaling of q-th order structure functions on time scales longer than 5 years, suggests the occurrence of intermittent turbulence rather than classical Kolmogorov turbulence in the fluid core motions. These results are briefly discussed in connection with the existence of a strong magnetic field and drift-wave turbulence.
Inferences on the source mechanisms of the 1930 Irpinia (Southern Italy) earthquake from simulations of the kinematic rupture process
Authors: A. Emolo  , G. Iannaccone  , A. Zollo  , A. Gorini
Published: June 2021

We examine here a number of parameters that define the source of the earthquake that occurred on 23rd July 1930 in Southern Italy (in the Irpinia region). Starting from the source models proposed in different studies, we have simulated the acceleration field for each hypothesized model, and compared it with the macroseismic data. We then used the hybrid stochastic-deterministic technique proposed by Zollo et al. (1997) for the simulation of the ground motion associated with the rupture of an extended fault. The accelerations simulated for several sites were associated with the intensities using the empirical relationship proposed by Trifunac and Brady (1975), before being compared with the available data from the macroseismic catalogue. A good reproduction of the macroseismic field is provided by a normal fault striking in Apenninic direction (approximately NW-SE) and dipping 55° toward the SW.
Model of long-term seismogenesis
Authors: F. Evison  , D. Rhoades
Published: June 2021

A three-stage faulting model explains the observed quantitative relations between long-term precursory seismicity, mainshocks and aftershocks. Seismogenesis starts with the formation of a major crack, culminates in the corresponding major fracture and earthquake, and ends with healing. Crack formation is a self-organised critical phenomenon, and shear fracture is a delayed sequel to crack formation. It is postulated that the major crack generates a set of minor cracks, just as, later, the major fracture generates a set of minor fractures. Fracturing of the minor cracks raises the average seismicity level. By Mogis uniformity criterion, the major earthquake is delayed until the minor fractures have healed and the stress-field has regained relative uniformity. In accord with the scaling principle, the model applies at all magnitude levels. The size of any given initial crack determines the scale of the ensuing seismogenic process. A graphical technique of cumulative magnitude analysis gives a quantitative representation of the seismicity aspects of the model. Examples are given for large earthquakes in a region of continental collision and a subduction region. The principle of hierarchy is exemplified by the seismogenesis of a M 5.9 mainshock occurring entirely within the precursory stage of a M 7.0 mainshock. The model is capable of accommodating a variety of proposed shorter-term precursory phenomena.
The Kresna earthquake of 1904 in Bulgaria
Authors: N. N. Ambraseys
Published: June 2021

The Kresna earthquake in 1904 in Bulgaria is one of the largest shallow 20th century events on land in the Balkans. This event, which was preceded by a large foreshock, has hitherto been assigned a range of magnitudes up to M S = 7.8 but the reappraisal of instrumental data yields a much smaller value of M S = 7.2 and a re-assement of the intensity distribution suggests 7.1. Thus both instrumental and macroseismic data appear consistent with a magnitude which is also compatible with the fault segmentation and local morphology of the region which cannot accommodate shallow events much larger than about 7.0. The relatively large size of the main shock suggests surface faulting but the available field evidence is insufficient to establish the dimensions, attitude andamount of dislocation, except perhaps in the vicinity of Krupnik. This downsizing of the Kresna earthquake has important consequences for tectonics and earthquake hazard estimates in the Balkans.
A fast-moving feature of westward drift
Authors: D. R. Barraclough  , S. R. C. Malin
Published: June 2021

he dominant feature in the magnetic declination record at all European sites for which adequate data are available is a minimum between 1750 and 1860. The time of minimum at different sites correlates well with longitude and implies a westward drift rate of 0.61 ± 0.08° yr-1. This is greatly in excess of the widely adopted value of 0.18° yr-1 for global westward drift.
Magnetotelluric investigations of the seismically active region of Northwest Bohemia: preliminary results
Authors: D. Di Mauro  , G. Volpi  , A. Manzella  , A. Zaja  , N. Praticelli  , V. Cerv  , J. Pek  , A. De Santis
Published: June 2021

During 1997, within the framework of an Italian-funded scientific cooperation between Italy and the Czech Republic, a series of magnetotelluric (MT) soundings was carried out in the region of Northwest Bohemia (Czech Republic). This is one of the most seismically active areas in Central Europe, where micro-earthquake swarms frequently occur during the apparently quiescent intervals between large macro-seismic swarms. Fifteen MT stations were installed in an area of about 15 ´ 20 km2 where 80% of the seismicity of the entire region has been recorded since 1986. The area showed a high electromagnetic noise, possibly of high cultural origin from the nearby industrial zone of the Sokolov basin, which affected both the electric and the magnetic signals. The final data, carefully selected, were modeled by 2D and 3D techniques. The results show an extensive conductive structure in the depth range from 0.5 to 3 km. This structure could be connected with the locally buried granitic massif in the inhomogeneous metamorphic basement, probably accompanied by fracturation, thermo-metamorphism or paleofluids. Moreover, the presence of a conductive anomaly in the northern part of the investigated region could be linked to a lithological change in the metamorphic rocks (prevalence of phyllites over mica schists), which would even increase the effect of the granite.
Pattern of seismic deformation in the Western Mediterranean
Authors: S. Pondrelli
Published: June 2021

The seismic deformation of the Western Mediterranean was studied with the aim of defining the strain pattern that characterizes the Africa-Eurasia plate boundary in this area. Within different sections along the boundary the cumulative moment tensor was computed over 90 years of seismological data. The results were compared with NUVELlA plate motion model and geodetic data. A stable agreement was found along Northern Africa to Sicily, where only Africa and Eurasia plates are involved. In this zone it is evident that changes in the strike of the boundary correspond to variations in the prevailing geometry of deformation, tectonic features and in the percentage of seismic with respect to total expected deformation. The geometry of deformation of periadriatic sections (Central to Southern Apennines, Eastern Alps and the Eastern Adriatic area) agrees well with VLBI measurements and with regional geological features. Seismicity seems to account for low rates, from 3% to 31%, of total expected deformation. Only in the Sicily Strait, characterized by extensional to strike slip deformation, does the ratio reach a higher value (79%). If the amount of deformation deduced from seismicity seems low, because 90 years are probably not representative of the recurrence seismic cycle of the Western Mediterranean, the strain pattern we obtain from cumulative moment tensors is more representative of the kinematics of this area than global plate motion models and better identifies lower scale geodynamic features.
A new geomagnetic observatory at Livingston Island (South Shetland Islands): Implications for future regional magnetic surveys
Authors: J. M. Torta  , L. R. Gaya-Piqué  , J. G. Sole  , I. Bianco  , A. Garcia
Published: June 2021

A pennanent geomagnetic observatory is always the ideal reference station for monitoring geomagnetic activity during airborne, marine or ground magnetic surveying, especially in Antarctica, where logistic difficulties are an important factor even for the deployment of temporary base stations. The utility of the magnetic observatory records for the correct reduction of the survey data is reinforced if both their spatial homogeneity and their particular anomaly biases are assessed. This, combined with data from the magnetic surveys themselves, can yield information on the crustal contribution to the Earth's magnetic field from a remote and poorly understood region. With these objectives in mind, we present a new geomagnetic observatory in the South Shetland Islands, where (because of the complex regional tectonic characteristics) magnetic surveys on one or another structure are conducted from time to time. An evaluation of the observatory representativeness and a look at the crustal magnetic anomaly ambience are also given.
Near-field seismic displacement and tilt associated with the explosive activity of Stromboli
Authors: E. Wielandt  , T. Forbriger
Published: June 2021

Broadband seismic recordings in the near-field of Strombolian explosions, at 500 m distance, show pronounced effects of tilt. The tilt signal is predominant in the horizontal components beyond about 50 s period while it is negligible in the vertical component. The waveform of the tilt signal at the seismometer output is a double time integral of the waveform due to ground displacement. Since the waveform of the displacement is known from the vertical component, the waveform of the tilt signal in the horizontal seismogram can be reconstructed and both contributions can be separated from each other with a linear regression. We have analyzed data recorded in the summit region of Stromboli in 1995 and 1996. The regional tilt can be determined from the differential vertical displacement between instruments a few tens of meters apart. Local tilts determined with individual instruments scatter around the regional value, most probably due to local strain-tilt-coupling. Mogi's (1958) formulae for a pressure source in a homogeneous halfspace are used to interpret the results. The source displaces a volume of several tens of cubic meters of the surrounding rock before the explosive discharge; typical volumes were 25 m3 in July 1995 and 60 m3 in September 1996.
The mechanics of Campi Flegrei unrests as related to plastic behaviour of the caldera borders
Authors: S. M. Petrazzuoli  , C. Troise  , F. Pingue  , G. De Natale
Published: June 2021

We present here a model which explains the mechanism of generation of unrest episodes at Campi Flegrei caldera from a mechanical point of view. The mechanism involves the effects of plastic zones at the borders of the inner collapsed area on both static deformations and seismicity. The large amount of ground uplift observed necessarily calls for plastic effects. These effects are interpreted as concentrated at the caldera borders: the generation of such plastic zones is simulated in terms of the mechanisms leading to the caldera collapse. In order to simulate the influence of such plastic zones on both ground deformations and seismicity we model them as surfaces of discontinuities free from shear stress within an elastic homogeneous half-space. The presence of such discontinuities allows the inner caldera block to move differentially from the outer areas, by slip along the plastic bordering zones. Such a differential uplift of the central block causes the concentration of the ground deformation. Our model explains a lot of puzzling observations at Campi Flegrei in terms of the effects of the caldera structure. The model is applicable to other caldera areas, which show typical evidence for the effects of such discontinuity zones, during unrest episodes.
Giuseppe Imbò and his contribution to volcano seismology
Authors: R. Schick
Published: June 2021

Together with Fusakichi Omori and Kenzo Sassa, Giuseppe Imbò is one of the founders of volcano seismology. Imbò's novel idea in volcanic tremor analysis was the introduction of what he called "numeri indici dell'intensità eruttiva" (numerical indices of the eruptive intensity). It was one of the first attempts to quantify eruptive activity on the basis of seismic data. The indices permitted him to establish correlations at Mt. Vesuvius between seismic observations and eruptive phenomena. He found significant differences in the character of the recorded seismic signals between pre- and post-eruptive phases of effusive and explosive activity of the March 1944 eruption of Vesuvius. According to Imbò, volcanic tremors are the product of a rhythmic hammering caused by the degassing magma normal to the vertically-oriented walls of the feeding conduits.
The temporal and spatial variations of low frequency geomagnetic pulsations at polar cusp and cap latitudes
Authors: N. G. Kleimenova  , P. Francia  , U. Villante  , O. V. Kozyreva  , J. Bitterly  , J. J. Schott
Published: June 2021

Geomagnetic field measurements at two Antarctic stations are compared during two weeks in the local summer (January 1-15, 1992). Low frequency (0.6-6 mHz) pulsations are observed at each station near local magnetic noon. The same wave packets appear in some cases also at the other station, although with a significant attenuation, more clearly in the morning sector; the waves show a near noon reversal of the polarization sense from counter-clockwise in the morning to clockwise in the afternoon indicating a westward and an eastward propagation, respectively.
Stress tensor inversion in Western Greece using earthquake focal mechanisms from the Kozani-Grevena 1995 seismic sequence
Authors: A. A. Kiratzi
Published: June 2021

Stress tensor inversion has been applied to estimate principal stress axes orientations in Western Greece, from 178 earthquake fault plane solutions from the Kozani-Grevena May 13, 1995 sequence. All focal mechanisms were previously determined through the deployment of a dense portable array. The magnitude range is 2.7-6.5 and the depth range is 4.0-15 km. A single stress tensor with an average misfit of 6.5°, small enough to support the assumption of stress homogeneity, can describe the stress field. The maximum compressive stress, s1, has a NNE-SSW trend (N26°E) and a nearly vertical plunge (80°) while the minimum compressive stress, s3, has a NNW-SSE orientation (N159°E) and a shallow plunge (7°) southwards. The scalar quantity, R (stress ratio) was found equal to 0.4 suggesting a transtensional regime (normal faulting with strike-slip motions) in which s2 is compressional. The identification of the fault plane from the auxiliary plane was achieved for 99 fault plane solutions out of 178 in total (56%). Vertical cross sections support previous results concerning the north dipping main fault segments and the south dipping antithetic faulting. The strike-slip motion is mainly dextral, along NNE-SSW structures, which follow the direction of the main neotectonic faults while the scarce sinistral strike-slip motion is connected to NW-SE trending zones of weakness pre-existing the old phase of compression in the Aegean. The strong strike slip motion that supports the transtensional regime probably reflects the effect of the motions of the North Anatolian Fault, taken up by normal faulting in the area of Western Greece.
A review of nonparametric attenuation functions computed for different regions of Italy
Authors: R. R. Castro  , M. Mucciarelli  , G. Monachesi  , F. Pacor  , R. Berardi
Published: June 2021

We used a set of previously published nonparametric attenuation functions to calculate average functions for the Italian region. These nonparametric functions describe the spectral amplitude decay of the S waves as a function of distance for 14 frequencies between 1 and 20 Hz for the regions of Lombardia-Piemonte, Eastern Sicily, Friuli, Marche and the Central Apennines. Since all the attenuation functions were obtained using the same methodology, we were able to make a fair comparison of the attenuation characteristics of the different regions. In general, while the Central Apennines show the strongest amplitude decay for all the frequencies analyzed, the regions of Lombardia and Eastern Sicily show the smallest attenuation. The Marche region also shows a strong amplitude decay, particularly for frequencies f > 3 Hz, and in the frequency band between 1 and 3 Hz the rate of decay of the spectral amplitudes with distance becomes similar to that of the region of Friuli. Since the attenuation functions analyzed represent different geologic and tectonic environments, we used them to calculate an average set of attenuation functions, one per frequency, for the hypocentral distance range between 10 and 120 km. The resulting functions permit a mean attenuation correction to spectral records of S waves in regions of Italy where the specific values of the attenuation parameters are unknown.
Chandler wobble excitation by catastrophic flooding of the Black Sea
Authors: G. Spada  , L. Alfonsi  , E. Boschi
Published: June 2021

It is now widely accepted that during the late Quaternary glaciation the Black Sea formed an isolated inland lake (Ross et al., 1970). New geological data and the recognition of sudden population movements away from the Black Sea coasts suggest that the basin was rapidly flooded through the Bosphorus sill 7150 years bp, causing a sea level rise of ~ 135 m in a few years (Ryan et al., 1997). As shown here, such a catastrophic redistribution of mass has significantly altered the amplitude of the Chandler wobble, the free motion of the pole of rotation around the main inertia axis of the Earth (Lambeck, 1980). We also estimate that during the flooding the pole of rotation was diverted from its secular path and shifted by ~ 30 m, at a rate of several meters per year. These rotational variations are found to be orders of magnitude larger than those produced by other short-term geophysical processes, such as earthquakes seismic moment release (O'Connell and Dziewonski, 1979; Chao et al.,1996), anthropogenic water impoundment (Chao, 1995), and tectonic mass movements (Alfonsi and Spada, 1998). The Black Sea flooding may thus be responsible for the most drastic change in the rotational parameters of the Earth in the recent history of our planet.
Analysis of multidimensional geophysical monitoring time series for earthquake prediction
Authors: A. A. Lyubushin
Published: June 2021

A method is presented for detection of synchronous signals in multidimensional time series data. It is based on estimation of eigenvalues of spectral matrices and canonical coherences in moving time windows and extraction of an aggregated signal (a scalar signal, which accumulates in its own variations only those spectral components which are present simultaneously in each scalar time series). It is known that an increase in the collective behavior of the components of some systems and an enlarged spatial radius of fluctuations of their parameters could be regarded as an important precursor of an oncoming catastrophe, i.e. abrupt change of the system's parameter values. From that point of view, detection of synchronous signals in various geophysical parameters, measured at points of some network, covering a given area of the Earth's crust, is of interest for identifying precursors of strong earthquakes. Some examples are presented of the use of this technique in the processing of real geophysical time series.
On the existence of earthquake precursors
Authors: F. Evison
Published: June 2021

Earthquake prediction based on precursors can aim to provide fully quantified, time-varying, synoptic forecasts, which do not depart from physical and geological principles, and are amenable to formal testing. These features are in contrast to the traditional occultist or soothsayer style of prediction. The recently-advanced, pre-emptive hypothesis that earthquakes are intrinsically unpredictable, and precursors non-existent, is also amenable to testing: it is refuted by the well-known relations between mainshocks and aftershocks. These relations show that a set of aftershocks is to a high degree predictable from the mainshock, so that, as a matter of principle, the mainshock is a precursor to its aftershocks. This result is compatible with the power-law property of seismicity, on which the unpredictability hypothesis is based. Empirical research on most precursors is difficult because of the scarcity of data, and is still largely at the anecdotal stage. Additional difficulties at the experimental stage are exemplified by the failure of the Tokai and Parkfield experiments to advance the study of precursors as planned. A comparative abundance of data is available on seismicity anomalies, and research on this type of precursor is progressing towards the operational stage.
A scheme for the preparation of strong induced seismic events
Authors: V. A. Mansurov  , B. Ts. Manjikov
Published: June 2021

A scheme of rockburst preparation is proposed from an analysis of induced seismicity."Rigid" inclusion is the basis of this scheme. Intensive destruction of the inclusion begins when a critical flaw concentration is reached in the volume. The size of the inclusion volume before destruction determines the maximum possible rockburst energy. It is very difficult to determine the place, where the main discontinuity will propagate, thus rockburst location may be determined only within the accuracy of a nucleus-zone size. The results obtained show: a) maximal localization of the failure process in a space occurs during the preparation of the dynamic event, and localization of the failure process in a time follows; b) the period of preparation of a high energy event has discontinuity values scatter less then during the subsequent period; c) both the average size of discontinuity and its variation ratio have good forecasting capability.
The fine structure of the dynamics of seismicity before earthquakes in the area of Reggio Emilia (Northern Italy)
Authors: R. Di Giovambattista  , Y. Tyupki
Published: June 2021

We present the results of studies of seismicity in the Reggio Emilia area (Northern Italy). The Istituto Nazionale di Geofisica instrumental earthquake catalogue (1975-1996) reported about three moderate-size earthquakes with M ³ 4.5 that occurred in this area (November 1983, May 1987, October 1996). The RTL prognostic parameter proposed by Sobolev and Tyupkin (1996a) was used for analysis. This parameter is designed in such a way that a seismic quiescence produces negative anomaly of the RTL parameter in comparison to its perennial background level and an activation of seismicity initiates the growth of its value. The RTL prognostic parameter indicates that all three earthquakes are preceded by activation of the seismicity. The interval between the commencement of the activation identified by RTL parameter and the event itself was about one year for the 1987 and 1996 earthquakes, and about three months for the 1983 earthquake.
Seismic hazard assessment in Eastern and Southern Africa
Authors: V. Midzi  , D. J. Hlatywayo  , L. S. Chapola  , F. Kebede  , K. Atakan  , D. K. Lombe  , G. Turyomurugyendo  , F. A. Tugume
Published: June 2021

Seismic hazard assessment for the Eastern and Southern Africa region was done using the probabilistic approach. Seismic hazard maps for 10% exceedance in 50 years, 10% exceedance in 100 years, as well as for 50 and 100 years return periods were prepared using the FRISK88M software. The area involved covers a wide region bounded by latitudes 40°S-25°N and longitudes 10°E and 55°E. Input parameters for the computations were obtained using the recent earthquake catalogue compiled by Turyomurugyendo. The catalogue which covers the time period 627-1994, contains earthquakes within the area bounded by 40°S-25°N and 10°E-55°E, with homogeneous magnitudes (M S ). Since a Poisson model of earthquake occurrence is assumed, dependent events were cleaned from the catalogue. Attenuation relations for the Eastern and Southern Africa region based on the strong motion data are virtually non-existent. However, attempts have been made recently by Jonathan and Twesigomwe to establish an average attenuation relation for the region. These relations were used in the computations. Possible uncertainties in the attenuation relations were accounted for using the logic-tree formalism. The results are presented in seismic hazard maps in terms of Peak Ground Acceleration (PGA) for the mean and the 85th percentile. The distribution of PGA values indicate relatively high hazard along the East African rift system. In the northern segments of the rift system, they exceed 250 gals for 10% probability of exceedence in 50 years.
Seismic hazard map of North and Central America and the Caribbean
Authors: K. M. Shedlock
Published: June 2021

Minimization of the loss of life, property damage, and social and economic disruption due to earthquakes depends on reliable estimates of seismic hazard. National, state, and local governments, decision makers, engineers, planners, emergency response organizations, builders, universities, and the general public require seismic hazard estimates for land use planning, improved building design and construction (including adoption of building construction codes), emergency response preparedness plans, economic forecasts, housing and employment decisions, and many more types of risk mitigation. The seismic hazard map of North and Central America and the Caribbean is the concatenation of various national and regional maps, involving a suite of approaches. The combined maps and documentation provide a useful regional seismic hazard framework and serve as a resource for any national or regional agency for further detailed studies applicable to their needs. This seismic hazard map depicts Peak Ground Acceleration (PGA) with a 10% chance of exceedance in 50 years. PGA, a short-period ground motion parameter that is proportional to force, is the most commonly mapped ground motion parameter because current building codes that include seismic provisions specify the horizontal force a building should be able to withstand during an earthquake. This seismic hazard map of North and Central America and the Caribbean depicts the likely level of short-period ground motion from earthquakes in a fifty-year window. Short-period ground motions effect short-period structures (e.g., one-to-two story buildings). The highest seismic hazard values in the region generally occur in areas that have been, or are likely to be, the sites of the largest plate boundary earthquakes.
Are different M = a + bI0 relationships due to a statistical bias?
Authors: M. Mucciarelli
Published: June 2021

Relationships between magnitude and macroseismic intensity are widely used, even though intensity is a non-metric observable. Several proposed relationships for the Italian and surrounding regions show a significant correlation of the parameters of the widely used functional form M = a + bI0 This could suggest either the common dependence on a third variable or that the different proposed relationships are due to a pivotal phenomenon around average values, mainly driven by data sampling and uncertainties. Synthetic simulations lend support to the last hypothesis.
Forecast of solar maximum and minimum dates for solar cycles 23 to 29
Authors: A. G. Elias  , N. Ortiz de Adler
Published: June 2021

The solar cycle length for cycles 23 to 29 are forecasted. Two methods are analysed. In the first one, the solar cycle length is separated into its two phases í the rise time and the fall off time í and a multiple regression method is applied to each phase using lagged values as independent variables. In the second method, the multiple regression is fitted directly to the solar cycle length. The minimum and maximum solar activity dates are listed for the cycles predicted with the latter method which proves to be more accurate. Two lagged values appear in the multiple regression adjusted to the solar cycle length. One is associated with the Gleissberg period, also observed in the maximum sunspot number, and the other is coincident with one of the periodicities in the C14 time record, which is associated with solar activity variation
Some theoretical of ionospheric storms at middle latitudes
Authors: G. A. Mansilla  , J. R. Manzano
Published: June 2021

Neutral wind effects in the F2-region during geomagnetic storms are theoretically studied solving the continuity equation (with production and loss of electrons) by means of a numerical method. This study was made for storms with sudden commencement at different times of day and at different latitudes. The results show that the equatorward movements of neutral air produce either enhanced or depressed maximum electron density values which depend on the velocity of these winds when the perturbation occurs at diurnal hours. If the geomagnetic storm is present during the night, only enhanced values are observed.
Historical geomagnetic measurements in Romania
Authors: A. Soare  , G. Cucu  , M. M. Alexandrescu
Published: June 2021

Following studies which give complete compilations of declination and inclination data for some European sites, this paper presents the geomagnetic field behaviour in Bucharest, over more than two centuries. The paper also discusses all the early survey measurements (declination, D, inclination, I, horizontal component, H) made in Romania, since the end of the nineteenth century.
Some considerations on the state of Vesuvius in the Middle Ages and the precursors of the 1631 eruption
Authors: A. Nazzaro
Published: June 2021

The volcanologic literature concerning Vesuvius and its activity, since the great eruption of 1631, is particularly abundant and helpful in order to investigate topics of remarkable interest on the eruptive history of the Neapolitan volcano. One of these topics relates to the precursory phenomena of the eruption of 1631. This problem it is of great importance for a better knowledge of the eruptive trends of the volcano since the 1631 eruption is the reference for any Civil Defence plan regarding the Vesuvius volcano. In addition, knowledge of the medieval activity of Vesuvius is important because it furnishes useful data for research into some unfamiliar aspects of the volcano's history, e.g., the existence of a 1500 eruption and consequently the duration of the inactivity period before 1631. It is generally assumed that the precursors of this eruption occurred less than one month before its beginning. In particular, the earthquakes would have come about 10 days before the eruption. Moreover a soil uplift is reported about 20 days beforehand. On the basis of a careful analysis of some important sources, books and manuscripts, we will see that the outline of the phenomena was much more complex.
A P-wave velocity model of the upper crust of the Sannio region (Southern Apennines, Italy)
Authors: G. Iannaccone  , L. Improta  , P. Capuano  , A. Zollo  , G. Biella  , R. De Franco  , A. Deschamps  , M. Cocco  , L. Mirabile  , R. Romeo
Published: June 2021

This paper describes the results of a seismic refraction profile conducted in October 1992 in the Sannio region, Southern Italy, to obtain a detailed P-wave velocity model of the upper crust. The profile, 75 km long, extended parallel to the Apenninic chain in a region frequently damaged in historical time by strong earthquakes. Six shots were fired at five sites and recorded by a number of seismic stations ranging from 41 to 71 with a spacing of 1-2 km along the recording line. We used a two-dimensional raytracing technique to model travel times and amplitudes of first and second arrivals. The obtained P-wave velocity model has a shallow structure with strong lateral variations in the southern portion of the profile. Near surface sediments of the Tertiary age are characterized by seismic velocities in the 3.0-4.1 km/s range. In the northern part of the profile these deposits overlie a layer with a velocity of 4.8 km/s that has been interpreted as a Mesozoic sedimentary succession. A high velocity body, corresponding to the limestones of the Western Carbonate Platform with a velocity of 6 km/s, characterizes the southernmost part of the profile at shallow depths. At a depth of about 4 km the model becomes laterally homogeneous showing a continuous layer with a thickness in the 3-4 km range and a velocity of 6 km/s corresponding to the Meso-Cenozoic limestone succession of the Apulia Carbonate Platform. This platform appears to be layered, as indicated by an increase in seismic velocity from 6 to 6.7 km/s at depths in the 6-8 km range, that has been interpreted as a lithological transition from limestones to Triassic dolomites and anhydrites of the Burano formation. A lower P-wave velocity of about 5.0-5.5 km/s is hypothesized at the bottom of the Apulia Platform at depths ranging from 10 km down to 12.5 km; these low velocities could be related to Permo-Triassic siliciclastic deposits of the Verrucano sequence drilled at the bottom of the Apulia Platform in the Apulia Foreland.
SKS-wave splitting and upper mantle structure: results in the Southern Apennines
Authors: L. Margheriti
Published: June 2021

Shear wave splitting measures at six temporary stations in the Southern Apennines are computed analyzing fifteen events recorded during the spring and summer 1996, with magnitude greater than 5.8. The splitting parameters were measured using Silver and Chan's (1991) method only on SKS and SKKS phases. Evidence for strong seismic anisotropy was found at all the stations: delay times dt are generally larger than 1.5 s and fast directions Ø are quite variable in different geodynamic domains. NW-SE Ø average directions are found at stations on the mountain belt while at stations on the foredeep and foreland Ø is on average N-S. Changes in splitting parameters may be related to upper mantle structure, and particularly to the geometry of a fragmented lithosphere subducting beneath the Apennines.
Artificial neural network applications in ionospheric studies
Authors: L. R. Cander
Published: June 2021

The ionosphere of Earth exhibits considerable spatial changes and has large temporal variability of various timescales related to the mechanisms of creation, decay and transport of space ionospheric plasma. Many techniques for modelling electron density profiles through entire ionosphere have been developed in order to solve the "age-old problem" of ionospheric physics which has not yet been fully solved. A new way to address this problem is by applying artificial intelligence methodologies to current large amounts of solar-terrestrial and ionospheric data. It is the aim of this paper to show by the most recent examples that modern development of numerical models for ionospheric monthly median long-term prediction and daily hourly short-term forecasting may proceed successfully applying the artificial neural networks. The performance of these techniques is illustrated with different artificial neural networks developed to model and predict the temporal and spatial variations of ionospheric critical frequency, f0F2 and Total Electron Content (TEC). Comparisons between results obtained by the proposed approaches and measured f0F2 and TEC data provide prospects for future applications of the artificial neural networks in ionospheric studies.
Modern radar techniques and the hazard of meteoroids to space platforms
Authors: G. Cevolani
Published: June 2021

Modern radar techniques, and in particular ground based radars, are a powerful tool to observe space objects (natural meteoroids and artificial space debris) on account of their all-weather and day-and-night performance. Natural meteoroids are an important component of the near-Earth space environment and represent a potential risk for all Earth-orbiting space platforms, which could significantly increase in coincidence of enhanced (outburst or storm) activity of meteoroid streams. A review of the currently active meteoroid streams suggests that a few streams have shown a quasi-periodic outburst activity in the two last centuries and may even undergo a storm activity in the next few years. The Leonids, the most intense of meteor showers, present a potentially serious damage to spacecraft in November of 1998 and 1999, after the perihelion passage of the parent body. Impact probability values of storm meteoroids on space platforms in Low Earth Orbit (LEO) were calculated using the data recorded during systematic observational campaigns carried out by the FS radar facility Bologna-Lecce in Italy. Meteoroid flux predictions and directionality, and investigation on impact parameters at very high velocities (up to 71 km/s) for penetration, charge production and plasma generation, are relevant aspects to develop strategies for safe deployment of the near Earrth-orbiting space platforms.
Thermophysical properties of the Lipari lavas (Southern Tyrrhenian Sea)
Authors: V. Pasquale  , M. Verdoya  , P. Chiozzi  , R. Cabella  , D. Russo
Published: June 2021

Results of thermophysical investigations into the lavas of the island of Lipari (Southern Tyrrhenian Sea) are presented. Samples selected for laboratory measurements belong to four main magmatic cycles, which produced basaltic-andesitic, andesitic and rhyolitic lavas. The wet-bulk density and the thermal conductivity measured on 69 specimens range from 1900 to 2760 kg m-3 and from 1.02 to 2.88 W m-1 K-1, respectively. Porosity is never negligible and its influence on density is maximum in rhyolites of the third cycle. The thermal conductivity is also influenced by the amount of glass. Rhyolitic obsidians show values lower than other rhyolites, although the latter rocks have a larger average porosity. The radioactive heat production determined on 36 specimens varies with the rock type, depending on the amount of U, Th and K. In basic lavas of the first cycle its value is 0.95°± 0.30 mW m-3, while in rhyolites of the fourth cycle it attains 6.68°±0.61 mW m-3. A comparison between results of g-ray spectrometry and X-ray fluorescence points out that the assumption of equilibrium in the decay series of the isotopic elements seems fulfilled. The information obtained is useful not only for the interpretation of geophysical surveys but also for the understanding of the geochemical characteristics of lavas.
Gravity waves propagation in the thermosphere observed from electron density profile and total electron content measurements
Authors: M. Anzidei  , C. Bianchi  , L. Ciraolo  , M. Pezzopane  , C. Scotto
Published: June 2021

Ionospheric observations with five minute intervals between ionograms were made during a campaign from 19th to 23rd June 1996 at the Rome station (41.8N, 12.5E). The data obtained from ionospheric vertical sounding have been analysed together with the Total Electron Content (TEC) data obtained by the GPS receiver measurements. Both the apparatus were installed in the same station. Short periodicity phenomena occurring in the considered period were observed and interpreted as resulting from the propagation of AGWs in the thermosphere. TEC and electron density were then analysed during AGWs activity.