bluuebunny/crossref_metadata_2025 huggingface dataset:
Materials for the investigation of The Seismicity Of Algeria And Adjacent Regions during the twentieth century
Authors: D. Benouar
Published: June 2021

Dr. Benouar presents a full and integrated study of the recent seismicity of Algeria and adjacent regions during the twentieth century. He has amassed an impressive amount of macroseismic information pertaining to individual earthquakes, which he combines with instrumental information to reassess the origin parameters of each event. In any compilation of earthquakes it is the additional information beyond the bare accumulation of figures and facts that adds interest and social understanding to the scientific appreciation of the earthquakes themselves. For this it is necessary to know the local conditions, and Dr. Benouar brings out for us very vivid1y the differences between reporting procedures at different times this century, and the ensuing difficulties. It would be most difficult for an outsider to gather the information he presents, and he makes good use of his knowledge of his native land, as well as his professional training as an engineer. We thus learn of the reluctance of the colonial powers to report on damage or casualties outside those inflicted on the expatriate community, and the general difficulties of finding information about earthquakes that occurred during the wars of independence, at a time when effects of even major earthquakes were sometimes minor compared to those of the war itself. He also does not spare us details of political difficulties that arose during periods of reconstruction following recent earthquakes. This work is not restricted, however, to description. He examines the underlying tectonics of the area and deduces estimates of hazard and risk in various parts of the country. He then proceeds to examine the engineering consequences and discuss future needs for building codes and civil protection. Dr. Benouar has produced a work which could well form a model for those wishing to undertake comprelzensive studies of seismicity of other areas, and the measures needed to reduce the effects of catastrophic earthquakes.
A case study of detecting the triplet of 3S1 using superconducting gravimeter records with an alternative data preprocessing technique
Authors: Wen-Bin Shen  , Bo Wu
Published: June 2021

Due to their very low noise levels in the low frequency band (<1 mHz), superconducting gravimeters (SGs) are particularly suitable to observe long-period free oscillations of the Earth. This case study is dedicated to the detection of the triplet of the seismic normal mode 3S1 that was excited by the December 26, 2004, Sumatra-Andaman earthquake (Mw = 9.3). Some SG records and the Hilbert-Huang transformation are used as an alternative data preprocessing technique, instead of the traditional detiding method. After removal of atmospheric pressure effects from the original SG records, we applied the Hilbert-Huang transformation to the SG residues, to select the signals that included the frequency band of interest, and to construct a new data series. Then, by applying the multi-station experimental technique to five 273-h-long common new data series recorded at different SG stations, we clearly observed all of the three singlets of the mode 3S1, with the central singlet more evident compared to previous studies. Observations of the low-frequency modes 3S1 (n = 0, 1, 2, ...; l = = 1,2, ...) provide constraints on the inner and outer core structure. This case study provides an alternative data-preprocessing approach to observe the splitting frequencies of the low-frequency mode type 3S1 (n = 0, 1, 2, ...).
Temperature and pressure gas geoindicators at the Solfatara fumaroles (Campi Flegrei)
Authors: Giovanni Chiodini  , Rosario Avino  , Stefano Caliro  , Carmine Minopoli
Published: June 2021

Long time series of fluid pressure and temperature within a hydrothermal system feeding the Solfatara fumaroles are investigated here, on the basis of the chemical equilibria within the CO2–H2O–H2–CO gas system. The Pisciarelli fumarole external to Solfatara crater shows an annual cycle of CO contents that indicates the occurrence of shallow secondary processes that mask the deep signals. In contrast, the Bocca Grande and Bocca Nova fumaroles located inside Solfatara crater do not show evidence of secondary processes, and their compositional variations are linked to the temperature–pressure changes within the hydrothermal system. The agreement between geochemical signals and the ground movements of the area (bradyseismic phenomena) suggests a direct relationship between the pressurization process and the ground uplift. Since 2007, the gas geoindicators have indicated pressurization of the system, which is most probably caused by the arrival of deep gases with high CO2 contents in the shallow parts of the hydrothermal system. This pressurization process causes critical conditions in the hydrothermal system, as highlighted by the increase in the fumarole temperature, the opening of new vents, and the localized seismic activity. If the pressurization process continues with time, it is not possible to rule out the occurrence of phreatic explosions.
Linear models of dissipation whose Q is almost frequency independent
Authors: M. CAPUTO
Published: June 2021

Laboratory experiments and field observations indicate
that tlie Q of many non ferromagnetic inorganic solids is almost frequency
independent in the range 10' to 10~2 cps; although no single substance has
been investigated over the entire frequency spectrum. One of the purposes
of this investigation is to find the analytic expression of a linear dissipative
mechanism whose Q is almost frequency independent over large frequency
ranges. This will be obtained by introducing fractional derivatives in the
stress strain relation.
Since the aim of this research is to also contribute to elucidating the
dissipating mechanism in the earth free modes, we shall treat the cases of
dissipation in the free purely torsional modes of a shell and the purely
radial vibration of a solid sphere.
The theory is checked with the new values determined for the Q of
the spheroidal free modes of the earth in the range between 10 and 5 minutes
integrated with the Q of the Railegh waves in the range between 5 and 0.6
minutes.
Another check of the theory is made with the experimental values
of the Q of the longitudinal waves in an alluminimi rod, in the range between
10-5 and 10-3 seconds.
In both clicks the theory represents the observed phenomena very
satisfactory.
RSTVOLC implementation on MODIS data for monitoring of thermal volcanic activity
Authors: Teodosio Lacava  , Francesco Marchese  , Nicola Pergola  , Valerio Tramutoli  , Irina Coviello  , Mariapia Faruolo  , Rossana Paciello  , Giuseppe Mazzeo
Published: June 2021

An optimized configuration of the Robust Satellite Technique (RST) approach was developed within the framework of the ‘LAVA’ project. This project is funded by the Italian Department of Civil Protection and the Italian Istituto Nazionale di Geofisica e Vulcanologia, with the aim to improve the effectiveness of satellite monitoring of thermal volcanic activity. This improved RST configuration, named RSTVOLC, has recently been implemented in an automatic processing chain that was developed to detect hot-spots in near real-time for Italian volcanoes. This study presents the results obtained for the Mount Etna eruption of July 14-24, 2006, using the Moderate Resolution Imaging Spectroradiometer (MODIS) data. To better assess the operational performance, the RSTVOLC results are also discussed in comparison with those obtained by MODVOLC, a well-established, MODIS-based algorithm for hot-spot detection that is used worldwide.
Ukrainian geomagnetic repeat station network and results of the field work reduced to the epoch 2005.5
Authors: Valentyn Maksymchuk  , Myxailo Orlyuk  , Viktor Tregybenko  , Yurij Horodyskyy  , Dmytro Marchenko
Published: June 2021

The results of geomagnetic field components of the renewed Ukrainian repeat stations (RS) network are presented. The methods of absolute geomagnetic and astro-geodetic measurements are described. The reduction of geomagnetic field components is carried out to the 2005.5 epoch and a catalogue of RS is created. Maps of magnetic declination for the Ukraine are constructed and compared with results calculated by the IGRF-2005 model.

 
A simple statistical procedure for the analysis of radon anomalies associated with seismic activity
Authors: Hugo Gonçalves Silva  , Mourad Bezzeghoud  , Maria Manuela Oliveira  , António Heitor Reis  , Rui Namorado Rosa
Published: June 2021

This study presents an analysis of data from various radon anomalies that were compiled by Toutain and Baubron [1999], to investigate their relationships with the earthquake parameters of magnitude and distance from epicenter. The simple methodology applied here reveals significant and positive correlation between the duration of the radon anomalies and the ratio between the earthquake preparation radius and the distance between the sensor and the event epicenter. This shows an important relationship between seismic activity and duration of radon anomalies at a local scale. The consequences and implications of this relationship are discussed.
GPS measurement of active strains across the Apennines
Authors: Enrico Serpelloni  , Marco Anzidei  , Paolo Baldi  , Giuseppe Casula  , Alessandro Galvani
Published: June 2021

Geodetic data are providing a new prospective in studying active tectonic processes that are occurring in penin- sular Italy. In this paper we use a recently published GPS velocity solution, obtained by merging a data set of permanent and non-permanent networks spanning the 1991-2002 time interval, to provide new quantitative con- straints of the active deformation rates across the Apennines Chain and the Calabrian Arc. The velocity field, given with respect to a fixed Eurasian frame, has been used to compute horizontal strain-rates within polygonal regions that connect and include geodetic stations, and to draw velocity cross sections along 5 different profiles through this region. The computed strain-rates provide a picture of the regional deformation field, which is in agreement with other seismological and geological data, and show that the Apennines are mainly extending in a SW-NE direction, while in Calabria extension is NW-SE oriented. Indications of active shortening are present only in the outer Northern Apennines. The velocity profiles across the Northern and Southern Apennines, along the Tyrrhenian Sea and Calabria, provide a quantitative measurement of the active extension and shortening rates, which are taking up at a more local scale.
Soil-gas survey of liquefaction and collapsed caves during the Emilia seismic sequence
Authors: Alessandra Sciarra  , Barbara Cantucci  , Mauro Buttinelli  , Gianfranco Galli  , Manuela Nazzari  , Luca Pizzino  , Fedora Quattrocchi
Published: June 2021

The epicentral area of the Emilia seismic sequence is located in the Emilia-Romagna Region (northern Italy), 45 km from the city of Modena (Figure 1). This area is sited within thrust-related folds of the Ferrara Arc, which represent the most external part of the northern Apennines. This sector is considered as having been active during late Pliocene to early Pleistocene times [Scrocca et al. 2007] and encompasses also the Mirandola and Ferrara seismogenic sources [e.g., Burrato et al. 2003, Boccaletti et al. 2004, Basili et al. 2008]. The main sedimentary infilling of the Po Plain is represented by Pliocene–Pleistocene alluvial deposits (alternating fluvial sands and clays) that overlie a foredeep clastic sequence, with a total average thickness of 2 km to 4 km [e.g., Carminati et al. 2010]. Soon after the mainshock, several liquefaction phenomena coupled to ground fractures were observed in the epicentral area (e.g., San Carlo, Ferrara). Soil liquefaction is a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or other rapid loading. […] Collapsed caves reported in the literature and/or local press [e.g., Febo 1999, Martelli 2002] in the epicentral area were previously investigated by our research group in 2008, with several soil measurements of CO2 and CH4 fluxes. Immediately after the May 20, 2012, mainshock and during the Emilia seismic sequence, the collapsed caves were sampled again to determine any variations in these CO2 and CH4 fluxes. In this survey, newly formed collapsed caves were also found and measured (especially in the northern part of investigated area). […]
AIDA – Seismic data acquisition, processing, storage and distribution at the National Earthquake Center, INGV
Authors: Salvatore Mazza  , Alberto Basili  , Andrea Bono  , Valentino Lauciani  , Alfonso Giovanni Mandiello  , Carlo Marcocci  , Francesco Mariano Mele  , Stefano Pintore  , Matteo Quintiliani  , Laura Scognamiglio  , Giulio Selvaggi
Published: June 2021

On May 4, 2012, a new system, known as the AIDA (Advanced Information and Data Acquisition) system for seismology, became operational as the primary tool to monitor, analyze, store and distribute seismograms from the Italian National Seismic Network. Only 16 days later, on May 20, 2012, northern Italy was struck by a Ml 5.9 earthquake that caused seven casualties. This was followed by numerous small to moderate earthquakes, with some over Ml 5. Then, on May 29, 2012, a Ml 5.8 earthquake resulted in 17 more victims and left about 14,000 people homeless. This sequence produced more than 2,100 events over 40 days, and it was still active at the end of June 2012, with minor earthquakes at a rate of about 20 events per day. The new AIDA data management system was designed and implemented, among other things, to exploit the recent huge upgrade of the Italian Seismic Network (in terms of the number and quality of stations) and to overcome the limitations of the previous system.
High-rate (1 Hz to 20 Hz) GPS coseismic dynamic displacements carried out during the Emilia 2012 seismic sequence
Authors: Antonio Avallone  , Elisabetta D'Anastasio  , Enrico Serpelloni  , Diana Latorre  , Adriano Cavaliere  , Ciriaco D'Ambrosio  , Sergio Del Mese  , Angelo Massucci  , Gianpaolo Cecere
Published: June 2021

In May-July 2012, Emilia Romagna (northern Italy) was struck by a significant seismic sequence, which was characterized by two moderate-magnitude earthquakes: a Ml 5.9 event on May 20, 2012, at 02:03:53 UTC, and a Ml 5.8 event on May 29, 2012, at 07:00:03 UTC, about 12 km to the west of the first mainshock. The earthquake sequence produced a total of 20 casualties and severe and widespread damage, mainly to historical and commercial buildings. A detailed description of the seismic sequence can be found in Sco-gnamiglio et al. [2012, this volume]. The largest of the earthquake static displacements were recorded by tens of continuous global positioning system (cGPS) stations, as described in Serpelloni et al. [2012, this volume]. Most of these stations were operating with a sampling frequency of 1 Hz, and they belonged to scientific or commercial networks: RING (http://ring.gm.ingv.it); ITALPOS (http://smartnet.leica-geosystems.it); GeoTop (http://www.netgeo.it); Fondazione Geometri Emilia Romagna (http://www.gpsemiliaromagna.it; Lombardia [http://www.gpslombardia.it); and Veneto (http://147.162.229.63). Some hours after the first mainshock, the sampling frequency of the near-field RING stations (SBPO and MODE) were switched to 20 Hz, thus recording the coseismic displacements produced by the May 29, 2012, earthquake at higher frequency. This sampling frequency was previously used for the detection of coseismic dynamic displacements only for the Mw 9 Tohoku-Oki 2011 event [Colosimo et al. 2011b]. Thus, the 20-Hz-sampling displacements for the Tohoku-Oki 2011 earthquake and the May 29, 2012, Emilia event might represent important recordings to investigate coseismic contributions at frequencies higher than 1 Hz with GPS. In the present study, after the description of the high-rate GPS (HRGPS) data analysis, we will show and compare the preliminary results. Then, for the two mainshocks, we will compare the displacements recorded by the HRGPS (1 Hz up to 20 Hz) and the strong-motion time histories (100 Hz) at MODE, where the different instruments were approximately co-located (Figure 1, inset, relative distance of ca. 90 m). […]
Paleoseismological evidence for historical surface faulting in São Miguel island (Azores)
Authors: Rita Carmo  , José Madeira  , Ana Hipólito  , Teresa Ferreira
Published: June 2021

The Azores archipelago is located at the triple junction between the Eurasian, Nubian and North American lithospheric plates, whose boundaries are the Mid-Atlantic Ridge and the Azores-Gibraltar Fault Zone. São Miguel is the largest island of the archipelago and is located on the eastern part of the western segment of the Azores-Gibraltar Fault Zone. The Achada das Furnas plateau, located in the central part of the island, between Fogo and Furnas central volcanoes, is dominated by several WNW-ESE and E-W trending alignments of basaltic cinder cones. Two E-W trending scarps were identified by aerial photo interpretation. Transect trenches exposed two active normal faults-the Altiprado Faults – confirming the tectonic nature of the scarps. Several paleoearthquakes were deduced, most of which in historical times, producing 1.38 m and 0.48 m of cumulative displacement. Maximum expected magnitudes (MW) determined from slip per event range from 5.7 to 6.7. One of the events probably corresponds to the historical earthquake of October 22nd, 1522, the deadliest in the archipelago. Radiocarbon ages are in agreement with this interpretation.
Application of the Environmental Seismic Intensity scale (ESI 2007) and the European Macroseismic Scale (EMS-98) to the Kalamata (SW Peloponnese, Greece) earthquake (Ms=6.2, September 13, 1986) and correlation with neotectonic structures and active faults
Authors: Ioannis G. Fountoulis  , Spyridon D. Mavroulis
Published: June 2021

On September 13, 1986, a shallow earthquake (Ms=6.2) struck the city of Kalamata and the surrounding areas (SW Peloponnese, Greece) resulting in 20 fatalities, over 300 injuries, extensive structural damage and many earthquake environmental effects (EEE). The main shock was followed by several aftershocks, the strongest of which occurred two days later (Ms=5.4). The EEE induced by the 1986 Kalamata earthquake sequence include ground subsidence, seismic faults, seismic fractures, rockfalls and hydrological anomalies. The maximum ESI 2007 intensity for the main shock has been evaluated as IXESI 2007, strongly related to the active fault zones and the reactivated faults observed in the area as well as to the intense morphology of the activated Dimiova-Perivolakia graben, which is a 2nd order neotectonic structure located in the SE margin of the Kalamata-Kyparissia mega-graben and bounded by active fault zones. The major structural damage of the main shock was selective and limited to villages founded on the activated Dimiova-Perivolakia graben (IXEMS-98) and to the Kalamata city (IXEMS-98) and its eastern suburbs (IXEMS-98) located at the crossing of the prolongation of two major active fault zones of the affected area. On the contrary, damage of this size was not observed in the surrounding neotectonic structures, which were not activated during this earthquake sequence. It is concluded that both intensity scales fit in with the neotectonic regime of the area. The ESI 2007 scale complemented the EMS-98 seismic intensities and provided a completed picture of the strength and the effects of the September 13, 1986, Kalamata earthquake on the natural and the manmade environment. Moreover, it contributed to a better picture of the earthquake scenario and represents a useful and reliable tool for seismic hazard assessment.
Analysis of GPS water vapor variability during the 2011 La Niña event over the western Pacific Ocean
Authors: Wayan Suparta  , Ahmad Iskandar  , Mandeep Singh Jit Singh  , Mohd. Alauddin Mohd. Ali  , Baharudin Yatim  , Ahmad Norazhar Mohd Yatim
Published: June 2021

We analyzed the variability of global positioning system (GPS) water vapor during the 2011 La Niña events over the western Pacific Ocean. The precipitable water vapor (PWV) derived from the UMSK (Malaysia) GPS station was investigated and compared with four other selected GPS stations: NTUS (Singapore), PIMO (Philippines), BAKO (Indonesia) and TOW2 (Australia). Analysis of the correlation between PWV and the sea-surface temperature anomaly (SSTa) on a weekly basis for the three La Niña cases of January–February–March, August–September–October, and October–November–December was used as an indicator of the influence of the El Niño Southern Oscillation. A good relationship between GPS PWV and SSTa for the Niño 4 region, with correlation coefficients between -0.91 and -0.94, was observed for the August–September–October and October–November–December cases. During the 2011 La Niña events, the water vapor was seen to increase to about 8.39 mm for the October–November–December case, with decreases of about 4.20 mm for the remaining months, compared to the mean 2011 value. This implies that during these events, the precipitation in the western Pacific is increased, due to stronger easterly trade winds blowing along the eastern Pacific Ocean than along the western Pacific, and a mass of warm water moving westwards, thereby increasing the evaporation.
On the recovery and analysis of historical seismograms
Authors: Barbara Palombo  , Nicola Alessandro Pino
Published: June 2021

The analysis of historical seismograms has proven to be a fundamental tool to help with the definition of the seismic risk in specific regions. Indeed, modern quantitative reappraisal of relevant earthquakes that occurred before the 1960’s; i.e., prior to both the developments of modern recording instruments and the theoretical progress, has been essential for the assessment of the seismic potential of a source area. However, due to the characteristics (transducing and recording) of the old analog seismographs, the data available are affected by intrinsic uncertainties, and errors can be introduced during the processing of waveform digitization. These drawbacks can seriously influence the quality and reliability of an investigation. In general, no standard technique can be applied when dealing with historical seismograms. Thus, specific tests and cross-checks have to be designed to estimate the limits of each specific analysis. Here, we aim to provide an overview of the whole procedure while focusing on the most crucial steps, from the seismogram recovery to the application of modern techniques for the retrieval of the seismic source information. We also suggest possible checks for the robustness of the data and for the available instrument characteristics, with a description of the effects of various uncertainties on the results that can be obtained. We thus provide useful indications for the analysis of historical seismograms, and also for the correct interpretation of the resulting characteristics of the seismic source.
13 years of MOPITT operations: lessons from MOPITT retrieval algorithm development
Authors: Helen M. Worden  , M. N. Deeter  , D. P. Edwards  , J. Gille  , J. Drummond  , L. K. Emmons  , G. Francis  , S. Martínez-Alonso
Published: June 2021

The Measurements of Pollution in the Troposphere (MOPITT) instrument on the NASA Terra platform has now acquired over thirteen years of global tropospheric carbon monoxide (CO) observations, forming the longest satellite record for an important pollutant. [...]
Comparison of the MIPAS products obtained by four different level 2 processors
Authors: Piera Raspollini  , Enrico Arnone  , Flavio Barbara  , Bruno Carli  , Elisa Castelli  , Simone Ceccherini  , Bianca Maria Dinelli  , Anu Dudhia  , Michael Kiefer  , Enzo Papandrea  , Marco Ridolfi
Published: June 2021

MIPAS is a midinfrared Fourier Transform spectrometer that sounded the atmospheric emission at limb onboard the ENVISAT satellite. It was launched on 31 March 2002 in a sun-synchronous polar orbit of about 800 km altitude and operated until 8 April 2012. The limb scanning sequence observed by the instrument is made of spectra that sound the atmosphere at different tangent altitudes (the tangent altitude is the minimum altitude reached by the line of sight and is also the altitude from where most of the observed signal originates). The inversion of the measurements allows the determination of the vertical profiles of the atmospheric quantities of interest in the range of the tangent altitudes covered by the limb scanning sequence, which is 6-70 km for the nominal measurement mode. […]
Thirty years of precise gravity measurements at Mt. Vesuvius: an approach to detect underground mass movements
Authors: Giovanna Berrino  , Vincenzo d’Errico  , Giuseppe Ricciardi
Published: June 2021

Since 1982, high precision gravity measurements have been routinely carried out on Mt. Vesuvius. The gravity network consists of selected sites most of them coinciding with, or very close to, leveling benchmarks to remove the effect of the elevation changes from gravity variations. The reference station is located in Napoli, outside the volcanic area. Since 1986, absolute gravity measurements have been periodically made on a station on Mt. Vesuvius, close to a permanent gravity station established in 1987, and at the reference in Napoli. The results of the gravity measurements since 1982 are presented and discussed. Moderate gravity changes on short-time were generally observed. On long-term significant gravity changes occurred and the overall fields displayed well defined patterns. Several periods of evolution may be recognized. Gravity changes revealed by the relative surveys have been confirmed by repeated absolute measurements, which also confirmed the long-term stability of the reference site. The gravity changes over the recognized periods appear correlated with the seismic crises and with changes of the tidal parameters obtained by continuous measurements. The absence of significant ground deformation implies masses redistribution, essentially density changes without significant volume changes, such as fluids migration at the depth of the seismic foci, i.e. at a few kilometers. The fluid migration may occur through pre-existing geological structures, as also suggested by hydrological studies, and/or through new fractures generated by seismic activity. This interpretation is supported by the analyses of the spatial gravity changes overlapping the most significant and recent seismic crises.
Vesuvio civil protection exercise MESIMEX: survey on volcanic risk perception
Authors: Tullio Ricci  , Rosa Nave  , Franco Barberi
Published: June 2021

In October 2006 the European Civil Protection Exercise MESIMEX (Somma Vesuvio Mesimex – Major Emergency SIMulation Exercise) on volcanic risk took place at Vesuvio, promoted by Campania Region and coordinated by the Italian Civil Protection Department. The exercise was focused on the preparedness phase for a major volcanic emergency in the area of Vesuvio. An evacuation of a sample of 1800 inhabitants from the Vesuvio Red Zone was also tested during the drill because the emergency plan ensures the complete evacuation of the population from the higher risk zone before the onset of the eruption. During that event a survey on volcanic risk perception was carried out on the evacuated population in order to compare the results with the ones coming from a previous similar survey, using the same questionnaire, carried out on a wider sample of residents in the Vesuvio Red Zone few months before MESIMEX exercise. The aim was to point out any differences in population’s attitude towards volcanic risk after having received detailed information on the emergency plan and on the hazards and risk related to the reactivation of Vesuvio, and experiencing the exercise. 463 questionnaires were distributed to the population evacuated from the 18 municipalities of the Red Zone and participating to the exercise. Main results in comparing data from MESIMEX survey with the Vesuvio previous one, put in evidence how the general level of Vesuvio residents’ trust remains quite low, indicating that a continuous and effective effort has to be done by both scientific community and Civil Protection Department. Particular attention should be paid in education and outreach activities and in involving people in risk mitigation procedures, also through more frequent exercises.
Instrumental seismic catalogue of Mt. Etna earthquakes (Sicily, Italy): ten years (2000-2010) of instrumental recordings
Authors: Salvatore Alparone  , Vincenza Maiolino  , Antonino Mostaccio  , Antonio Scaltrito  , Andrea Ursino  , Graziella Barberi  , Salvatore D’Amico  , Giuseppe Di Grazia  , Elisabetta Giampiccolo  , Carla Musumeci  , Luciano Scarfì  , Luciano Zuccarello
Published: June 2021

Instrumental seismic catalogues are an essential tool for the zonation of the territory and the production of seismic hazard maps. They are also a valuable instrument for detailed seismological studies regarding active volcanoes and, above all, for interpreting the magma dynamics and the evolution of eruptive phenomena. In this paper, we show the first instrumental earthquake catalogue of Mt. Etna, for the period 2000-2010, with the purpose of producing a homogeneous dataset of 10 years of seismological observations. During this period, 16,845 earthquakes have been recorded by the seismic network run by the Istituto Nazionale di Geofisica and Vulcanologia, Osservatorio Etneo, in Catania. A total of 6,330 events, corresponding to approximately 40% of all earthquakes recorded, were located by using a one-dimensional VP velocity model. The magnitude completeness of the catalogue is equal to about 1.5 for the whole period, except for some short periods in 2001 and 2002-2003 and at the end of 2009. The reliability of the data collected is supported by the good values of the main hypocentral parameters through the time. The spatial distribution of seismicity allowed the highlighting of several seismogenetic areas characterized by different seismic rates and focal depths. This seismic catalogue represents a fundamental tool for several research aiming to a better understanding of the behavior of an active volcano such as Mt. Etna.

 
Limits on the potential accuracy of earthquake risk evaluations using the L’Aquila (Italy) earthquake as an example
Authors: John Douglas  , Daniel Monfort Climent  , Caterina Negulescu  , Agathe Roullé  , Olivier Sedan
Published: June 2021

This article is concerned with attempting to ‘predict’ (hindcast) the damage caused by the L’Aquila 2009 earthquake (Mw 6.3) and, more generally, with the question of how close predicted damage can ever be to observations. Damage is hindcast using a well-established empirical-based approach based on vulnerability indices and macroseismic intensities, adjusted for local site effects. Using information that was available before the earthquake and assuming the same event characteristics as the L’Aquila mainshock, the overall damage is reasonably well predicted but there are considerable differences in the damage pattern. To understand the reasons for these differences, information that was only available after the event were include within the calculation. Despite some improvement in the predicted damage, in particularly by the modification of the vulnerability indices and the parameter influencing the width of the damage distribution, these hindcasts do not match all the details of the observations. This is because of local effects: both in terms of the ground shaking, which is only detectable by the installation of a much denser strong-motion network and a detailed microzonation, and in terms of the building vulnerability, which cannot be modeled using a statistical approach but would require detailed analytical modeling for which calibration data are likely to be lacking. Future studies should concentrate on adjusting the generic components of the approach to make them more applicable to their location of interest. To increase the number of observations available to make these adjustments, we encourage the collection of damage states (and not just habitability classes) following earthquakes and also the installation of dense strong-motion networks in built-up areas.
Towards a cross-border exposure model for the Earthquake Model Central Asia
Authors: Marc Wieland  , Massimiliano Pittore  , Stefano Parolai  , Ulugbek Begaliev  , Pulat Yasunov  , Jafar Niyazov  , Sergey Tyagunov  , Bolot Moldobekov  , Saidislom Saidiy  , Indalip Ilyasov  , Tanatkan Abakanov
Published: June 2021

This work provides an insight into the development of the first harmonized exposure model for Central Asia. The model was derived in the frame of the Earthquake Model Central Asia (EMCA) project, which is the regional initiative for Central Asia to the Global Earthquake Model (GEM). The EMCA exposure model combines commonly used data sources and acquisition techniques (e.g., rapid visual screening) with novel rapid assessment approaches (e.g., satellite remote sensing and omnidirectional imaging) in the framework of an integrated sampling scheme and stores the data in a multi-resolution spatio-temporal database. The exposure model implements a newly developed building typology, harmonized for the five Central Asian countries (Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan) and follows the international building taxonomy of the GEM. Emphasis is given to the multi-scale nature and the temporal dynamics of exposure data. Results from a selected urban area are provided to illustrate the current state of the continuously updated exposure model.
Probabilistic seismic hazard assessment for Central Asia
Authors: Shahid Ullah  , Dino Bindi  , Marco Pilz  , Laurentiu Danciu  , Graeme Weatherill  , Elisa Zuccolo  , Anatoly Ischuk  , Natalya N. Mikhailova  , Kanat Abdrakhmatov  , Stefano Parolai
Published: June 2021

Central Asia is one of the seismically most active regions in the world. Its complex seismicity due to the collision of the Eurasian and Indian plates has resulted in some of the world’s largest intra-plate events over history. The region is dominated by reverse faulting over strike slip and normal faulting events. The GSHAP project (1999), aiming at a hazard assessment on a global scale, indicated that the region of Central Asia is characterized by peak ground accelerations for 10% probability of exceedance in 50 years as high as 9 m/s2. In this study, carried out within the framework of the EMCA project (Earthquake Model Central Asia), the area source model and different kernel approaches are used for a probabilistic seismic hazard assessment (PSHA) for Central Asia. The seismic hazard is assessed considering shallow (depth < 50 km) seismicity only and employs an updated (with respect to previous projects) earthquake catalog for the region. The seismic hazard is calculated in terms of macroseismic intensity (MSK-64), intended to be used for the seismic risk maps of the region. The hazard maps, shown in terms of 10% probability of exceedance in 50 years, are derived by using the OpenQuake software [Pagani et al. 2014], which is an open source software tool developed by the GEM (Global Earthquake Model) foundation. The maximum hazard observed in the region reaches an intensity of around 8 in southern Tien Shan for 475 years mean return period. The maximum hazard estimated for some of the cities in the region, Bishkek, Dushanbe, Tashkent and Almaty, is between 7 and 8 (7-8), 8.0, 7.0 and 8.0 macroseismic Intensity, respectively, for 475 years mean return period, using different approaches. The results of different methods for assessing the level of seismic hazard are compared and their underlying methodologies are discussed.
Global Seismic Hazard Assessment Program - GSHAP legacy
Authors: Laurentiu Danciu  , Domenico Giardini
Published: June 2021

Global Seismic Hazard Assessment Program - or simply GSHAP, when launched, almost two decades ago, aimed at establishing a common framework to evaluate the seismic hazard over geographical large-scales, i.e. countries, regions, continents and finally the globe. Its main product, the global seismic hazard map was a milestone, unique at that time and for a decade have served as the main reference worldwide. Today, for most of the Earth’s seismically active regions such Europe, Northern and Southern America, Central and South-East Asia, Japan, Australia, New Zealand, the GSHAP seismic hazard map is outdated. The rapid increase of the new data, advance on the earthquake process knowledge, technological progress, both hardware and software, contributed all in updates of the seismic hazard models. We present herein, a short retrospective overview of the achievements as well as the pitfalls of the GSHAP. Further, we describe the next generation of seismic hazard models, as elaborated within the Global Earthquake Model, regional programs: the 2013 European Seismic Hazard Model, the 2014 Earthquake Model for Middle East, and the 2015 Earthquake Model of Central Asia. Later, the main characteristics of these regional models are summarized and the new datasets fully harmonized across national borders are illustrated for the first time after the GSHAP completion.
Seismic monitoring of Campi Flegrei and Vesuvius by stand-alone instruments
Authors: Mario La Rocca  , Danilo Galluzzo
Published: June 2021

A seismic network of more than 20 broad band stations and two arrays of 10 short period stations each, all working in local acquisition mode, are used to improve the seismic monitoring of Campi Flegrei and Vesuvius for research purposes. Data provided by stand-alone instruments are characterized by high quality and very continuous data streams, therefore they are appropriate to detect and analyze any seismic signals possibly related with the volcanic activity. Array data are particularly useful to discover and analyze seismic events characterized by low amplitude, low signal to noise ratio and emergent onset, but whose signals are more coherent among the array stations than the background noise. Since the background seismic signal is very high at both volcanoes, particularly at Campi Flegrei, seismic arrays and dense station networks are necessary to discriminate volcanic events from the many transient signals produced by artificial sources. In Campi Flegrei area the analysis with array methods of data recorded by ARF array permitted the discovery of low amplitude volcanic tremor of hydrothermal origin occurred in January 2015, a seismic signal never observed before in the area. At Mt. Vesuvius the analysis of VAS array data has shown the occasional occurrence of short bursts of low amplitude volcanic tremor. Small low-frequency earthquakes have also been revealed in the two volcanic areas.
Multi-quasi-parabolic ionosphere model with EF-valley
Authors: Jie Sun  , Xiao-Juan Zhang  , Shun Wang  , Zhao-Qian Gong  , Guang-You Fang
Published: June 2021

We improve the conventional multi-quasi-parabolic (MQP) model and develop two MQP models with EF-valley by applying the predicted EF-valley parameter of the newest version of the International Reference Ionosphere. On the basis of the conventional MQP model and these two improved MQP models with EF-valley, we generate one-hop oblique sounding ionograms between Wuhan and Beijing. Comparisons between the generated ionograms and the sounding ionogram in the experiments illustrate that the improved MQP models are more suitable for describing the true ionosphere than the conventional MQP model is. In contrast to the conventional MQP model, the improved MQP models can increase the accuracy of ray tracing and reduce the errors in shortwave single location and over-the-horizon-radar registration.
Natural radioactivity content in groundwater of Mt. Etna’s eastern flank and gamma background of surrounding rocks.
Authors: Beata Kozłowska  , Agata Walencik-Łata  , Giuseppina Immè  , Roberto Catalano  , Gabriella Mangano  , Daniela Morelli  , Salvatore Giammanco
Published: June 2021

Waters of Mt. Etna are the main source of drinking water for the local population and are also distributed in municipal supply systems to neighbouring areas. Radioactivity in underground waters and surrounding rocks from the eastern flank of Mt.Etnawas investigated on the basis of 9 water and 8 rocks samples from 12 localities altogether. Three samples were from water drainage galleries and six from water wells. All water intakes are used for consumption. Activity concentration of uranium isotopes 234,238U, radium isotopes 226,228Ra and radon 222Rn were determined with the use different nuclear spectrometry techniques. The determination of uranium isotopes was carried out with the use of alpha spectrometry. The measurements of radium and radon activity concentration in water were performed with the use of a liquid scintillation technique. Additionally, rocks surrounding the intakes were examined with gamma spectrometry. All water samples showed uranium concentration above Minimum Detectable Activity (MDA), with the highest total uranium (234U + 238U) activity concentration equal to 149.2±6 mBq/L. Conversely, all samples showed radium isotopes activity concentrations below MDA. Radon activity concentration was within the range from 2.91±0.36 to 21.21±1.10 Bq/L, hence these waters can be classified as low – radon waters. Gamma natural background of the rocks surrounding the water sampling sites was found on the same levels as other volcanic rocks of Italy.
Eighteen years of GPS surveys in the Aeolian Islands (southern Italy): open data archive and velocity field
Authors: Alessandra Esposito  , Grazia Pietrantonio  , Valentina Bruno  , Marco Anzidei  , Alessandro Bonforte  , Francesco Guglielmino  , Mario Mattia  , Giuseppe Puglisi  , Vincenzo Sepe  , Enrico Serpelloni
Published: June 2021

Since the early 1970s, geodetic networks became a most important tool to monitor the present day deformations of the volcanic arc of the Aeolian Islands. The first benchmarks were installed in this region at Lipari and Vulcano Islands and the number of GPS benchmarks increased in time since the early ’90s. These networks were periodically surveyed in the frame of national and international geodynamic projects and for Civil Protection programs devoted to the mitigation of the volcanic hazard. The Istituto Nazionale di Geofisica e Vulcanologia (INGV) played a fundamental role in the realization and periodical reoccupation of these networks, with the goal to investigate the tectonic and volcanic processes, still active in this crucial area of the central Mediterranean. An updated GPS velocity map for this region, both for the horizontal and vertical component of land motion, with details for Lipari, Vulcano and Panarea Islands, is provided in this paper. The presented GPS velocity field also includes a set of additional discrete stations located in northern Sicily and Calabria together with data from the available CGPS networks active in southern Italy. Here we show the results from eighteen years of repeated GPS surveys performed in this region in the time span 1995-2013 and the open access AINET-GPS data archive, now freely available for the scientific community. Data will support scientific research and hopefully improve the assessment of volcanic and seismic hazard in this region.
Moment tensor inversion of early instrumental data: application to the 1917 High Tiber Valley, Monterchi earthquake
Authors: Fabrizio Bernardi  , Maria Grazia Ciaccio  , Barbara Palombo  , Graziano Ferrari
Published: June 2021

In this paper we present a new study on the High Tiber Valley earthquake occurred on April 26, 1917. Using the digitized data from mechanical seismograph records, we computed the source parameters like focal mechanism and moment magnitude from moment tensor (MT). The study of historical earthquakes from an instrumental perspective is crucial because of the complexity of problems associated with the study of seismograms of moderate to large earthquakes occurred from the late 19th century until the early 1960s. Since historical earthquake records show significant uncertainties in phase arrival times and have been recorded by seismograph generally with short natural period, we developed a code to compute the MT based on a forward modeling technique, which uses the amplitude spectra of the full waveform length and the first P-arrival polarities to constrain the P- and T-axes. The best solution is determined by the best fit between the observed and synthetic amplitude spectra and from the coherency between the observed and the theoretical first P-arrival polarities. The 1917 High Tiber Valley earthquake is one of the most important 20th century earthquake occurred in the Italian Peninsula for which the focal mechanism and moment magnitude from seismic records are not available. Additionally, we apply a multidisciplinary approach to characterize the source of this earthquake, combining instrumental, macroseismic, geological and tectonic data and investigations. The computed MT results in a north-south normal fault mechanism (strike: 147°, dip: 29°, slip: −94°), which is consistent with the strike estimated from the macroseismic data (157°). The moment magnitude calculated from the MT and that derived from the macroseismic data are Mw=5.5±0.2 and Mw=5.9±0.1, respectively.
Criticality features in ultra-low frequency magnetic fields prior to the 2013 M6.3 Kobe earthquake
Authors: Stelios M. Potirakis  , Konstantinos Eftaxias  , Alexander Schekotov  , Hiroki Yamaguchi  , Masashi Hayakawa
Published: June 2021

The nonlinear criticality of ultra-low frequency (ULF) magnetic variations is investigated before a particular earthquake (EQ) occurred in Kobe on April 12, 2013, by applying the “natural time” analysis on a few ULF parameters: Fh, Fz and Dh. The first two refer to radiation from the lithosphere, and the last parameter corresponds to depression of horizontal component as a signature of ionospheric perturbation. A recent paper of our team has indicated, using the same data as in this paper but by means of conventional statistical analysis, a clear effect of depression in the horizontal component as an ionospheric signature. But there seems to be no convincing signature of lithospheric ULF radiation according to the specific analysis, so this paper aims at extending our study on the electromagnetic data recorded prior to the specific EQ by trying to find any significant phenomenon in ULF effects (both lithospheric radiation and the depression of horizontal component) using the critical, natural time analysis. The natural time analysis has yielded that criticality at Shigaraki (SGA), as the station closest to the EQ epicenter, is reached on March 27-29 for Fh and March 27 to April 1 for Fz (about two weeks before the EQ). But, the criticality for Dh was not observed at SGA probably due to high noise, on the other hand such criticality was observed at Kanoya (KNY) because of its known property of a wider range of detection of ULF depression.
Preliminary macroseismic survey of the 2016 Amatrice seismic sequence
Authors: Mariano Angelo Zanini  , Lorenzo Hofer  , Flora Faleschini  , Paolo Zampieri  , Nicola Fabris  , Carlo Pellegrino
Published: June 2021

After the recent destructive L’Aquila 2009 and Emilia-Romagna 2012 earthquakes, a sudden Mw 6.0 seismic event hit Central Italy on August 24, 2016. A low population density characterizes the area but, due to its nighttime occurrence, about 300 victims were registered. This work presents the first preliminary results of a macroseismic survey conducted by two teams of the University of Padova in the territories that suffered major damages. Macroseismic intensities were assessed according to the European Macroseismic Scale (EMS98) for 180 sites.