ALBERT

Description: In recent decades, geological modeling has significantly evolved, relying on the growing potential of hardware and software to manage and integrate vast datasets of 2D-3D geophysical underground data. Therefore, digitization and integration with other forms of data can often improve understanding of geological systems, even when using so-called vintage or historical data. Seismic reflection data have been extensively acquired mainly for hydrocarbon exploration since the 60s generating large volumes of data. Typically, these data have been for private commercial use and are relatively unavailable for research. However, with time, large volumes of vintage seismic reflection data in many countries worldwide are now becoming publicly available through time-based de-classification schemes. Such data have a great potential for modern-day geo-research, unleashing opportunities to improve geological understanding through re-interpretation with modern methods. However, a downside of these vintage data is that they are often only available in analog (paper, raster) format. The vectorization of these data then constitutes an essential step for unlocking their research potential. In 2018 INGV established the SISMOLAB-3D infrastructure, which is mainly devoted to analyzing digital subsurface data, such as seismic reflection profiles and well-logs, to build 2D-3D geological models, principally for seismotectonics, seismic hazard assessment, and geo-resources applications. In this contribution, we discuss the robustness of the WIGGLE2SEGY code, firstly published by Sopher in 2018, focusing on examples from different tectonic and geodynamic contexts within Italian territory. We applied the SEG-Y conversion method to onshore and offshore raster seismic profiles related to ceased exploration permits, comparing the results with other published archives of SEG-Y data obtained from the conversion of vintage data. Such an approach results in digital SEG-Y files with unprecedented quality and detail. The systematic application of this method will allow the construction of a comprehensive dataset of digital SEG-Y seismic profiles across Italy, thereby expanding and sharing the INGV SISMOLAB-3D portfolio with the scientific community to foster innovative and advanced scientific analysis.

Description: Published

Description: DM538

Description: 1TR. Georisorse

Description: 2TR. Ricostruzione e modellazione della struttura crostale

Description: 2IT. Laboratori analitici e sperimentali

Description: JCR Journal

Description: Southwestern Sicily is an area of infrequent seismic activity; however, some studies carried out in the archaeological Selinunte site suggest that, between the fourth century BC and the early Middle Ages, probably at least two earthquakes strucked this area with enough energy to damage and cause the collapse and kinematics of much of the architecture of Selinunte. Take into account that, in 2008, a noninvasive archaeological prospection and traditional data gathering methods along the Acropolis north fortifications were carried out. Following these first studies, after about 10 years, a new geophysical campaign was carried out. This second campaign benefited from the application of modern technologies for the acquisition and processing of the point cloud data on the northern part of the Acropolis, like terrestrial laser scanning and unmanned aerial vehicle photogrammetry. In this paper, we present the application of these techniques and a strategy for their integration for the 3D modelling of buildings and cultural heritages. We show how the integration of data acquired independently by these two techniques is an added value able to overcome the intrinsic limits of the individual techniques. The application to Selinunte's Acropolis allowed it to highlight and measure with high accuracy fractures, dislocation, inclinations of walls, depressions of some areas and other interesting observations, which may be important starting points for future investigations.

Description: Published

Description: 153-165

Description: 2IT. Laboratori analitici e sperimentali

Description: JCR Journal

Description: Monitoring of hydrothermal fluid emissions can provide detailed information about convective upwelling of geothermal fluids and their geochemical characteristics, as a function of tectonic stress or deeper gas input. In particular, at the Salinelle of Mt. Etna Geosite (Paternò and Belpasso, Eastern Sicily) natural emissions mainly consist of a fluid phase made of salty water, mud, gas and liquid hydrocarbons from an admixture of magmatic and hydrothermal gases. In this framework, our study mainly focused on the thermal and geochemical monitoring of hydrothermal fluids of the most active site, Salinelle dei Cappuccini. Nearby hydrothermal vents (Salinelle del Fiume; Salinelle di San Biagio), were also investigated. Analysis of the magnitude and frequency of seismic events all around Mt. Etna were conducted as well. Analysis of daily temperatures showed a constant trend: higher values (〉 35° C) within the first monitoring period, followed by a strong decrease (down to 9° C), and a new gradual increase over the following months. This trend seems to be linked to magmatic processes occurring at depth below Mt. Etna, and could lead to a modification of the geochemical and thermal characteristics of the fluids issuing at the mud-pools and gas vents of Salinelle. The higher the frequency of seismic events corresponding to higher daily energy released, the higher fluid temperatures observed. Understanding how these fluids blend and what is their relationship with Mt. Etna volcanism can be of great importance in forecasting new eruptive cycles in the case they precede changes in volcanic activity.

Description: Published

Description: GD670

Description: 7A. Geofisica per il monitoraggio ambientale

Description: JCR Journal

Description: The response of continental forelands to subduction and collision is a widely investigated topic in geodynamics. The deformation occurring within a foreland shared by two opposite‐verging chains, however, is uncommon and poorly understood. The Apulia Swell in the southern end of the Adria microplate (Africa‐Europe plate boundary, central Mediterranean Sea) represents one of these cases, as it is the common foreland of the SW verging Albanides‐Hellenides and the NE verging Southern Apennines merging into the SSE verging Calabrian Arc. We investigated the internal deformation of the Apulia Swell using multiscale geophysical data: multichannel seismic profiles recording up to 12‐s two‐way time (TWT) for a consistent image of the upper crust; high‐resolution multichannel seismic profiles, high‐resolution multibeam bathymetry, and CHIRP profiles acquired by R/V OGS Explora to constrain the Quaternary geological record. The results of our analyses characterize the geometry of the South Apulia Fault System (SAFS), a 100‐km‐long and 12‐km‐wide structure attesting an extensional (and possibly transtensional) response of the foreland to the two contractional fronts. The SAFS consists of two NW‐SE right‐stepping master faults and several secondary structures. The SAFS activity spans from the Early Pleistocene through the Holocene, as testified by the bathymetric and high‐resolution seismic data, with long‐term slip rates in the range of 0.2–0.4 mm/yr. Considering the position within an area with few or none other active faults in the surroundings, the dimension, and the activity rates, the SAFS can be a candidate causative fault of the 20 February 1743, M 6.7, earthquake.

Description: Italian Ministry for Education, University, and Research (MIUR), Premiale 2014 D. M. 291 03/05/2016.

Description: Published

Description: e2020TC006116

Description: 2T. Deformazione crostale attiva

Description: 2TR. Ricostruzione e modellazione della struttura crostale

Description: JCR Journal

Description: Over fifty eruptive episodes with Strombolian activity, lava fountains, and lava flows occurred at Mt Etna volcano between 2006 and 2013. Namely, there were seven paroxysmal lava fountains at the South-East Crater in 2007-2008 and 46 at the New South-East Crater between 2011 and 2013. Lava emissions lasting months affected the upper eastern flank of the volcano in 2006 and 2008-2009. Effective monitoring and forecast of such volcanic phenomena are particularly relevant for their potential socio-economic impact in densely populated regions like Catania and its surroundings. For example, explosive activity has often formed thick ash clouds with widespread tephra fall able to disrupt the air traffic, as well as to cause severe problems at infrastructures, such as highways and roads. Timely information about changes in the state of the volcano and possible onset of dangerous eruptive phenomena requires efficacious surveillance methods. The analysis of the continuous background seismic signal, the so-called volcanic tremor, turned out of paramount importance to follow the evolution of volcanic activity [e.g., Alparone et al., 2003; Falsaperla et al., 2005]. Changes in the state of the volcano as well as in its eruptive style are usually concurrent with variations of the spectral characteristics (amplitude and frequency) of tremor. The huge amount of digital data continuously acquired by INGV’s broadband seismic stations every day makes a manual analysis difficult. In order to tackle this problem, techniques of automatic classification of the tremor signal are applied. In a comparative study, the robustness of different methods for the identification of regimes in volcanic activity were examined [Langer et al., 2009]. In particular, Langer et al. [2011] applied unsupervised classification techniques to the tremor data recorded at one station during seven paroxysmal episodes in 2007-2008. Their results revealed significant changes in the pattern classification well before the onset of the eruptive episodes. This evidence led to the development of specific software packages, such as the program KKAnalysis [Messina and Langer, 2011], a software that combines an unsupervised classification method (Kohonen Maps) with fuzzy cluster analysis. The operational characteristics of these tools - fail-safe, robustness with respect to noise and data outages, as well as computational efficiency - allowed on-line processing at the operative centre of the INGV-Osservatorio Etneo in 2010 and the identification of criteria for automatic alarm flagging. The system is hitherto one of the main automatic alerting tools to identify impending eruptive events at Etna. The software carries out the on-line processing of the new data stream coming from two seismic stations, merged with reference datasets of past eruptive episodes. In doing so, results obtained for new data are immediately compared to previous eruptive scenarios. Given the rich material collected in recent years, we are able to apply the alert system to eleven stations at different elevations (1200-3050 m) and distances (1-8 km) from the summit craters. Critical alert parameters were empirically defined to obtain an optimal tuning of the alert system for each station. To verify the robustness of this new, multistation alert system, a dataset encompassing about eight years of continuous seismic records (since 2006) was processed automatically using KKAnalysis and collateral software off-line. Then, we analyzed the performance of the classifier in terms of timing and spatial distribution of the stations. We also investigated the performance of the new alert system based on KKAnalysis in case of activation of whatever eruptive centre. Intriguing results were obtained in 2010 throughout periods characterized by the renewal of volcanic activity at Bocca Nuova-Voragine and North-East Crater, and in the absence of paroxysmal phenomena at South-East Crater and New South-East Crater. Despite the low-energy phenomena reported by volcanologists (i.e., degassing, low-to moderate explosions), the triggered alarms demonstrate the robustness of the classifier and its potential: i) to identify even subtle changes within the volcanic system using tremor, and ii) to highlight the activation of a single eruptive centre, even though different from the one for which the classifier was initially tested. It is worth noting that in case of activation of weak sources, the successful performance of the classifier depends upon the general level of signals originating from other sources in that specific time span.

Description: Published

Description: Nicolosi (Catania, Italy)

Description: 2V. Dinamiche di unrest e scenari pre-eruttivi

Description: open

Description: Mt. Etna is permanently active requiring a continuous data acquisition a multidisciplinary monitoring system where huge data masses accumulate and pose severe difficulties of interpretation. Therefore the INGV staff has developed a number of software tools for data mining, aiming at identifying structures in the data which can be related to the volcanic activity and furnish criteria for the definition of alert systems. We tackle the problem by applying methods of clustering and classification. We identify data groups by defining a measure of similarity or distance. Data groups may assume various shapes, once forming convex clouds once complex concave bodies. The tool “KKAanalysis” is a basket of clustering methods and forms the backbone of the tremor-based automatic alarm system of INGV-OE. It exploits both SOM and Fuzzy Clustering. Besides seismic data the concept has been applied to petrochemic data as well as in a combined analysis of gas-emission data and seismic data. The software “DBSCAN” focuses on density-based clustering that allows discovering clusters with arbitrary shape. Here, clusters are defined as dense regions of objects in the data space separated by regions of low density. In DBSCAN a cluster grows guaranteeing that the density within a group of objects exceeds some threshold. In the context of volcano monitoring the method is particularly promising in the recognition of ash particles as they have a rather irregular shape. The “MOTIF” software allows identifying typical wave forms in time series. It overcomes shortages of methods like cross- correlation, which entail a high computational effort. MOTIF on the other hand can recognize non-similarity of two patterns on a small number of data points without going through the whole length of the data vectors. The development includes modules for feature extraction and post-processing verifying the validity of the results obtained by the classifiers.

Description: Published

Description: Nicolosi (Catania, Italy)

Description: 2V. Dinamiche di unrest e scenari pre-eruttivi

Description: open

Description: Timely identification of changes in the state of volcanoes and onset of potentially dangerous eruptive phenomena requires efficacious surveillance methods. In the case of an active volcano like Mt Etna, the continuous background seismic signal called volcanic tremor is of paramount importance. The huge amount of continuously acquired digital data entails the necessity of data reduction and parameter extraction. For this purpose, techniques of automatic analysis of volcanic tremor were applied by INGV for the real time monitoring of this signal. We checked the possibility to identify regimes of volcanic activity based on pattern classification of volcanic tremor. A specific software named “KKAnalysis” was developed. It combines various unsupervised classification methods (Kohonen Maps and fuzzy cluster analysis) and forms the backbone of an automatic alert system at INGV-OE. Besides its near real time application, it can be operated off-line, allowing an efficient a-posteriori processing of data and tuning of the alarm criteria to match specific needs of sensitivity and robustness. An ongoing development of this tool will allow us to include a large number of seismic stations in a multistation-alarm system. The new system will be more robust in case of failure of single sensors, and will achieve a better coverage of the various eruptive craters. In an off-line test, we exploited a dataset covering eight years of seismic records, and analysed the performance of the new system in terms of “trigger timing” and spatial distribution of the stations. Intriguing results were obtained throughout periods of renewal of volcanic activity at Bocca Nuova-Voragine and North East Crater, and in the absence of paroxysmal phenomena at South East Crater and New South East Crater.

Description: Published

Description: Nicolosi (Catania, Italy)

Description: 2V. Dinamiche di unrest e scenari pre-eruttivi

Description: open

Description: In questo lavoro viene descritta l’installazione di una rete mobile nell’area dei Monti Nebrodi in seguito all’evento del 23-06-2011 di Ml = 4.6 e come tale intervento ha contribuito al miglioramento della localizzazione delle sorgenti sismiche soprattutto nella determinazione della profondità degli eventi. Verranno anche presentati i risultati delle localizzazioni ottenute attraverso l’integrazione dei dati acquisiti durante questa campagna, con quelli della rete sismica permanente dell’INGV-Osservatorio Etneo ( INGV -OE).

Description: Istituto Nazionale di Geofisica e Vulcanologia

Description: Published

Description: 1-24

Description: 4IT. Banche dati

Description: N/A or not JCR

Description: open

Description: The global positioning system (GPS) phase scintillation caused by highlatitude ionospheric irregularities during an intense high-speed stream (HSS) of the solar wind from April 29 to May 5, 2011, was observed using arrays of GPS ionospheric scintillation and total electron content monitors in the Arctic and Antarctica. The one-minute phase-scintillation index derived from the data sampled at 50 Hz was complemented by a proxy index (delta phase rate) obtained from 1-Hz GPS data. The scintillation occurrence coincided with the aurora borealis and aurora australis observed by an all-sky imager at the South Pole, and by special sensor ultraviolet scanning imagers on board satellites of the Defense Meteorological Satellites Program. The South Pole (SP) station is approximately conjugate with two Canadian High Arctic Ionospheric Network stations on Baffin Island, Canada, which provided the opportunity to study magnetic conjugacy of scintillation with support of riometers and magnetometers. The GPS ionospheric pierce points were mapped at their actual or conjugate locations, along with the auroral emission over the South Pole, assuming an altitude of 120 km. As the aurora brightened and/or drifted across the field of view of the all-sky imager, sequences of scintillation events were observed that indicated conjugate auroras as a locator of simultaneous or delayed bipolar scintillation events. In spite of the greater scintillation intensity in the auroral oval, where phase scintillation sometimes exceeded 1 radian during the auroral break-up and substorms, the percentage occurrence of moderate scintillation was highest in the cusp. Interhemispheric comparisons of bipolar scintillation maps show that the scintillation occurrence is significantly higher in the southern cusp and polar cap.

Description: Published

Description: R0216

Description: 1.7. Osservazioni di alta e media atmosfera

Description: 3.9. Fisica della magnetosfera, ionosfera e meteorologia spaziale

Description: JCR Journal

Description: open

Description: In recent years, several groups have installed high-frequency sampling receivers in the southern middle and high latitude regions, to monitor ionospheric scintillations and the total electron content (TEC) changes. Taking advantage of the archive of continuous and systematic observations of the ionosphere on L-band by means of signals from the Global Positioning System (GPS), we present the first attempt at ionospheric scintillation and TEC mapping from Latin America to Antarctica. The climatology of the area considered is derived through Ground-Based Scintillation Climatology, a method that can identify ionospheric sectors in which scintillations are more likely to occur. This study also introduces the novel ionospheric scintillation 'hot-spot' analysis. This analysis first identifies the crucial areas of the ionosphere in terms of enhanced probability of scintillation occurrence, and then it studies the seasonal variation of the main scintillation and TEC-related parameters. The results produced by this sophisticated analysis give significant indications of the spatial/ temporal recurrences of plasma irregularities, which contributes to the extending of current knowledge of the mechanisms that cause scintillations, and consequently to the development of efficient tools to forecast space-weather-related ionospheric events.

Description: Published

Description: R0220

Description: 1.7. Osservazioni di alta e media atmosfera

Description: 3.9. Fisica della magnetosfera, ionosfera e meteorologia spaziale

Description: JCR Journal

Description: open

Description: The electronic space weather upper atmosphere (eSWua) is a hardware– software system that is based on measurements collected by instruments installed by the Upper Atmosphere Physics Group of the Istituto Nazionale di Geofisica e Vulcanologia (INGV, Italy). More recently, it has also included the Global Navigation Satellite System (GNSS) ionospheric scintillation and total electron content (TEC) monitor (GISTM) stations that are managed and operated by the University of Nottingham (UK). By visiting the eSWua website, it is possible to access the database that has been implemented to organize and manage the large amount of information acquired. The section of the database designed for the TEC and scintillation data has been designed to address the needs of the space weather community as well as of scientific users. Through the web tools, it is possible to visualize, plot, extract and download the data from each station. This interactive website is supported by a structured database, and it provides a powerful tool for the scientific and technological community in the field of telecommunications and space weather. At present, the data transmission procedure, the database population algorithm, the linear plot and polar plot visualization tools, the statistics page, and the user management system are fully operational. Web access to the data and tools has been realized to handle the data from the sites at low, mid and high latitudes. In this report, we present the results of the system for the GNSS data in the Arctic, the Antarctica, and the three GISTM stations operated by the University of Nottingham: Nottingham, Trondheim and Dourbes. Case studies of the efficacy of this system for scientific and application purposes are also presented and discussed.

Description: Published

Description: R0223

Description: 1.7. Osservazioni di alta e media atmosfera

Description: 5.4. Banche dati di geomagnetismo, aeronomia, clima e ambiente

Description: JCR Journal

Description: open

Description: Twenty-five lava fountains occurred on Mt. Etna from January 2011 to April 2012. In summer 2012 volcanic activity resumed in a milder form within the Bocca Nuova crater, before it came to an essential halt in August 2012. All these unrests offer rich material for testing automatic procedures of data processing and alert systems, running 24/7, in the context of volcano surveillance. We focus on the seismic background radiation – volcanic tremor – which plays a key role in the monitoring of Mt. Etna. Since 2006 a multistation alert system has been established in the INGV operative centre of Catania exploiting STA/LTA ratios. Besides, also the spectral characteristics of the signal, which change correspondingly to the type of volcanic activity, can be exploited for warning purposes. Here we apply Self Organizing Maps and Fuzzy Clustering which offer an efficient way to visualize signal characteristics and its development with time. All these techniques allow to identify early stages of eruptive events, and automatically flag a critical status before this becomes evident in conventional monitoring techniques. Changes of tremor characteristics are related to the position of the source of the signal. The location of the sources exploits the distribution of the amplitudes across the seismic network. The locations were extremely useful for warning, throughout both the flank eruption in 2008 as well as the 2011 lava fountains, during which a clear migration of tremor sources towards the eruptive centres could be noticed in advance. The location of the sources completes the picture of an imminent volcanic unrest, and corroborates early warnings flagged by the changes of signal characteristics. Real time data processing requires computational efficiency, robustness of the methods and stability of data acquisition. The amplitude based multi-station approach is not sensitive to the failure of single stations and therefore offers a good stability. The single station approach, exploiting unsupervised classification techniques, limits logistic efforts, as only one or few key stations are necessary. Both strategies have proven to be insensitive to disturbances (undesired transients like earthquakes, noise, short gaps in the continuous data flow). False alarms were not encountered so far. Stable data acquisition and processing come with a properly designed data storage solution. The reliability of data storage and its access is a critical issue. A cluster architecture has been realized for failover protection, including a Storage Area Network system, which allow easy data access following predefined user policies. We present concepts of the software architectures deployed at INGV Osservatorio Etneo in order to implement this tremor-based multi approach system. We envisage the integration of seismic data and those originating from other scientific fields (e. g., volcano imagery, geochemistry, deformation, gravity, magneto-telluric). This will facilitate cross-checking of evidences encountered from the single data streams, in particular allow their immediate verification with respect to ground truth.

Description: Published

Description: Nicolosi (Catania, Italy)

Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive

Description: 5.6. TTC - Attività di Sala Operativa

Description: open

Description: In the framework of the project BIS - Bipolar Ionospheric Scintillation and Total Electron Content Monitoring, the ISACCO-DMC0 and ISACCO-DMC1 permanent monitoring stations were installed in 2008. The principal scope of the stations is to measure the ionospheric total electron content (TEC) and to monitor the ionospheric scintillations, using high-sampling-frequency global positioning system (GPS) ionospheric scintillation and TEC monitor (GISTM) receivers. The disturbances that the ionosphere can induce on the electromagnetic signals emitted by the Global Navigation Satellite System constellations are due to the presence of electron density anomalies in the ionosphere, which are particularly frequent at high latitudes, where the upper atmosphere is highly sensitive to perturbations coming from outer space. With the development of present and future low-frequency space-borne microwave missions (e.g., Soil Moisture and Ocean Salinity [SMOS], Aquarius, and Soil Moisture Active Passive missions), there is an increasing need to estimate the effects of the ionosphere on the propagation of electromagnetic waves that affects satellite measurements. As an example, how the TEC data collected at Concordia station are useful for the calibration of the European Space Agency SMOS data within the framework of an experiment promoted by the European Space Agency (known as DOMEX) will be discussed. The present report shows the ability of the GISTM station to monitor ionospheric scintillation and TEC, which indicates that only the use of continuous GPS measurements can provide accurate information on TEC variability, which is necessary for continuous calibration of satellite data.

Description: Published

Description: R0219

Description: 1.7. Osservazioni di alta e media atmosfera

Description: 1.10. TTC - Telerilevamento

Description: 3.9. Fisica della magnetosfera, ionosfera e meteorologia spaziale

Description: JCR Journal

Description: open

Description: In questo lavoro si presentano i risultati di uno studio sulle caratteristiche del rumore sismico in prossimità del rilevatore di onde gravitazionali VIRGO (Cascina, Pisa), con particolare riferimento alle vibrazioni associate all’azione di un vicino parco eolico. La valutazione delle componenti spettrali del rumore verosimilmente indotte dagli aerogeneratori è stata effettuata mediante (i) Misure dirette alla base di una turbina, (ii) Correlazione fra le ampiezze spettrali del rumore e la velocità del vento; (iii) Determinazione delle proprietà direzionali da misure multicanale, (iv) Misura dell’attenuazione del segnale con la distanza dal parco eolico. Il disturbo provocato dagli aerogeneratori è particolarmente energetico alla frequenza di 1.7 Hz e, in particolari condizioni, è stato osservato fino a distanze di 11 km dal Parco Eolico. Il decadimento spaziale delle ampiezze ha un andamento complesso, che può essere interpretato in termini di una combinazione fra onde superficiali e onde di volume rifratte ad un’interfaccia profonda (~800 m) fra i sedimenti plio-pleistocenici ed i calcari Miocenici. La risposta locale nei dintorni dell’interferometro è stata investigata utilizzando la tecnica dei rapporti spettrali H/V. Si sono così evidenziate due bande di amplificazione imputabili ad effetti di risonanza legati alla geologia a scala locale: il primo intorno alla frequenza di 0.35 Hz, il secondo fra 0.7 e 2.0 Hz. Entrambi i picchi risultano essere essenzialmente omogenei in tutta l’area di studio, a conferma della sostanziale uniformità della struttura geologica.

Description: Published

Description: 1-30

Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale

Description: N/A or not JCR

Description: open

Description: In questo lavoro viene descritto il complesso sistema di acquisizione dati della RSM [vedi D’Alema et al., 2011 - in questo volume], costituita da 58 stazioni collegate in tempo reale e 13 stazioni dial-up. I dati delle stazioni in tempo reale sono acquisiti con il programma Seiscomp31; la detezione degli eventi sismici viene eseguita con il programma Earthworm ed infine l’analisi e l’interpretazione degli eventi viene effettuata attraverso il programma SacPicker di Daniele Spallarossa [vedi Spallarossa, 2011 - in questo volume]. La parte di rete dial-up è basata sul sistema Lennartz Mars882 ed è configurata in modo autonomo dalla rete in tempo reale. I dati delle due reti vengono successivamente uniti in un unico dataset ai fini di una interpretazione interattiva congiunta.

Description: Published

Description: 124-127

Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale

Description: N/A or not JCR

Description: open

Description: Da alcuni anni l’INGV e la Regione Marche collaborano nell’azione di monitoraggio sismico del territorio regionale. Nella sede di Ancona del CNT sono acquisiti in tempo reale i segnali sismici di circa 80 stazioni dell’Italia centro-orientale. Si è reso pertanto necessario sviluppare applicativi utili al controllo degli apparati che compongono il sistema di monitoraggio. In particolare, vengono controllati: 1) lo stato di funzionamento delle trasmissioni radio ed ethernet; 2) lo stato dell’alimentazione delle stazioni e il numero di satelliti ricevuti dagli apparati GPS; 3) la quantità di segnale sismico archiviato e i gaps del segnale continuo; 4) i livelli di rumore di fondo e la qualità del segnale sismico.

Description: Published

Description: 104-107

Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale

Description: N/A or not JCR

Description: open

Description: A Pilot Project for CO2 injection and storage was proposed for a gas storage area located at Cortemaggiore (Piacenza), in northern Italy. This project is conducted both to verify the injection techniques and to analyze the potentiality of CO2 as a cushion gas. Starting from 2004, a series of analysis has been conducted to verify suitability and feasibility of this operation. The injection phase will be preceded by a passive seismic monitoring in order to measure the background seismicity of the area. Seismic monitoring will be carried out during the 3 years of the injection phase and will continue also for a control period of 2 years, following the working phase. The Milano - Pavia Department of the Istituto Nazionale di Geofisica e Vulcanologia is in charge of the surface seismic monitoring. To study the background seismicity a microseismic network composed by 7 seismic stations has been realized. On February 2010, a first test phase has been conducted for 3 sites. The network was completed with 4 more stations on May 2010. All stations are composed by a 24-bit digital recorder (Lennartz M24/NET) with GPS time signal. The study area is characterized by a very high anthropic and industrial noise. In order to improve the quality of the seismic signals, 4 stations have been installed in a 100 m deep borehole. The seismic sensors (Lennartz LE-3D/BH for the borehole and LE-3Dlite MKI for the installation at the surface) have similar technical characteristics with 1 Hz free period, cutoff frequency at 80 Hz and dynamic range of 136 dB. In this first stage we analyzed the microseismic noise level and evaluated the detection capability of the network. Using the RMS measurements the borehole stations indicate a reduction on the noise by a factor of 2.5. A more detailed analysis, performed using the density function distribution of the power spectra, evidences a 10 dB gain for the borehole stations in the frequency band 1 - 10 Hz. Noise measurements have been used also to determine the minimum magnitude for the events detection. Using a point source model to simulate seismic events, we verified the expected detection levels by comparing the estimates obtained with the simulation and the local events recorded by the seismic network.

Description: Published

Description: 12

Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale

Description: N/A or not JCR

Description: open

Description: Nell’ambito del progetto FIRB-Airplane [“Piattaforma di ricerca multidisciplinare su terremoti e vulcani”, fondi MIUR 2007-2011 responsabili: Cocco, Amato e Stucchi1] dalla seconda metà del 2009 è stata installata una rete densa di stazioni sismiche nell’area dell’Alta Val Tiberina (AVT, Figura 1), i cui dati in continuo vengono trasmessi alla sede di Ancona del CNT attraverso una dorsale Wi-Fi HYPERLAN [Monachesi e Cattaneo, 2010]. La rete è stata progettata cercando di rispettare alcuni criteri, tra cui: controllo continuo della funzionalità delle singole stazioni, flessibilità nella scelta dei siti, riduzione del rischio di fulminazioni, possibilità di abbinare stazioni sismiche e stazioni geodetiche. A tal fine sono stati adottati strumenti a basso consumo per quel che riguarda acquisitori e sistemi di trasmissione, accompagnati dall’utilizzo di sistemi di alimentazione autonomi e sistemi di telecontrollo

Description: Published

Description: 91-93

Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale

Description: N/A or not JCR

Description: open

Description: Attualmente presso la sede di Ancona del CNT sono acquisiti i dati relativi a 58 stazioni in realtime ed a 13 stazioni dial-up. In particolare la sede di Ancona ha la funzione di server nei confronti della sala sismica nazionale per 28 stazioni in realtime e client per le rimanenti 30. Le stazioni dial-up hanno una connessione con radio modem (8) o con modem GSM (5). Gli acquisitori gestiti sono: GAIA1 e GAIA2, Trident/Cygnus, HDR24 e Lennartz Mars88/MC/RC. I sensori sono: Trillium 40-120-240s; Lennartz LE3D- 5s/1s/lite/BH, Mark L4-3D, Episensor ES-T. Il sistema di acquisizione dati è basato su Seiscomp31, mentre la detezione degli eventi avviene tramite Earthworm

Description: Published

Description: 19-21

Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale

Description: N/A or not JCR

Description: open

Description: In this paper we investigate nature and properties of narrow-band, transient seismic signals observed by a temporary array deployed in the Val Tiberina area (central Apennines, Italy). These signals are characterized by spindle-shaped, harmonic waveforms with no clear S-wave arrivals. The first portion of the seismograms exhibits a main frequency peak centred at 4.5 Hz, while the spectrum of the slowly decaying coda is peaked at about 2 Hz. Events discrimination is performed using a matched-filtering technique, resulting in a set of 2466 detections spanning the 2010 January–March time interval. From a plane-wave-fitting procedure, we estimate the kinematic properties of signals pertaining to a cluster of similar events. The repetition of measurements over a large number of precisely aligned seismograms allows for obtaining a robust statistics of horizontal slownesses and propagation azimuths associated with the early portion of the waveforms. The P-wave arrival exhibits horizontal slownesses around 0.1 s km−1, thus suggesting waves impinging at the array almost vertically. Separately, we use traveltimes measured at a sparse network to derive independent constraints on epicentral location. Ray parameters and azimuths are calibrated using slowness measurements from a local, well-located earthquake. After this correction, the joint solution from traveltime inversion and array analysis indicates a source region spanning the 1–3 km depth interval. Considerations related to the source depth and energy, and the occurrence rate which is not related to the daily and weekly working cycles, play against a surface, artificial source. Instead, the close resemblance of these signals to those commonly observed in volcanic environments suggest a source mechanism related to the resonance of a fluid–filled fracture, likely associated with instabilities in the flux of pressurized CO2.

Description: Published

Description: 918-928

Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale

Description: JCR Journal

Description: reserved

Description: L’utilizzo di sensori in pozzo ha l’obiettivo di migliorare il rapporto segnale-disturbo per poter registrare segnali di eventi sismici in zone dove le registrazioni in superficie sono corrotte dai disturbi. Infatti, le registrazioni superficiali sono affette dal noise sismico ambientale il quale è particolarmente elevato in zone industrializzate a frequenze generalmente superiori ad 1 Hz [McNamara and Buland, 2004]. La RSN dell’INGV, gestita dal CNT [vedi Delladio, 2011 - in questo volume], è dotata attualmente di 6 sensori in pozzo, ubicati nelle seguenti località: Castelleone (CR), Imola (BO), Bellaria (RN), Senigallia (AN), Sansepolcro (AR), Città di Castello (PG). Le prime 4 località si trovano in pianura padana (Castelleone e Imola) e sulla costa adriatica (Bellaria e Senigallia): in questi siti l’utilizzo di un sensore in pozzo ha lo scopo di ottenere registrazioni in cui i disturbi antropici possano essere significativamente abbattuti, in quanto le aree citate sono tra le più industrializzate e urbanizzate del territorio nazionale [Marzorati and Bindi, 2006]. I pozzi di Sansepolcro e Città di Castello rientrano nell’area di interesse della Faglia Alto Tiberina, in cui terremoti di piccolissima magnitudo vengono registrati solo in siti particolarmente silenziosi dal punto di vista del noise sismico ambientale; perciò i due sensori in pozzo hanno lo scopo di avere un punto di osservazione più vicino alla sorgente dei segnali che si vogliono registrare. Nei prossimi paragrafi sono mostrati alcuni esempi utili per poter valutare l’efficienza dei sensori in pozzo.

Description: Published

Description: 72-75

Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale

Description: N/A or not JCR

Description: open

Description: In this paper the history of the Mobile Seismic Network of the Osservatorio Vesuviano (at present Department of Napoli of the Istituto Nazionale di Geofisica e Vulcanologia – INGV) is described. The instrumental development and the main research and monitoring activities since the early 1980’ are reported. Starting from the analog stations with magnetic tape recording to the first digital stations with trigger recording, until the modern multichannel 24bit devices, the technological development of the last 30 years has given a strong contribution to increase the knowledge in the seismology and seismotectonics fields. The Mobile Seismic Network has been engaged in active and passive seismic studies both on volcanic and tectonic areas. Particularly, the contribution of the Mobile Seismic Network for the monitoring of Neapolitan active volcanoes has been very important to improve the Permanent Network. During seismic crises high quality data have been gathered allowing detailed analyses of the seismic activity. Moreover, the time synchronization by means of GPS time code allowed the deployment of the Mobile Network abroad and the collaboration with the main international research institutes. At present, the Mobile Seismic Network of the Osservatorio Vesuviano is developing on multichannel acquisition systems, also in array configuration, to gathered simultaneously seismic signals with a large frequency band.

Description: Published

Description: 1-51

Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive

Description: 3.2. Tettonica attiva

Description: N/A or not JCR

Description: open

Description: An unusual nighttime impulsive electron density enhancement was observed on 6 March 2010 over a wide region of South America, below the southern crest of the equatorial anomaly, under low solar activity and quiet geomagnetic conditions. The phenomenon was observed almost simultaneously by the F2 layer critical frequency ( foF2) recorded at three ionospheric stations which are widely distributed in space, namely Cachoeira Paulista (22.4°S, 44.6°W, magnetic latitude 13.4°S), São José dos Campos (23.2°S, 45.9°W, magnetic latitude 14.1°S), Brazil, and Tucumán (26.9°S, 65.4°W, magnetic latitude 16.8°S), Argentina. Although in a more restricted region over Tucumán, the phenomenon was also observed by the total electron content (TEC) maps computed by usingmeasurements from 12 GPS receivers. The investigated phenomenon is very particular because besides being of brief duration, it is characterized by a pronounced compression of the ionosphere. This compression was clearly visible both by the virtual height of the base of the F region (h′F) recorded at the aforementioned ionospheric stations, and by both the vertical electron density profiles and the slab thickness computed over Tucumán. Consequently, neither an enhanced fountain effect nor plasma diffusion from the plasmasphere can be considered as the single cause of this unusual event. A thorough analysis of isoheight and isofrequency ionosonde plots suggest that traveling ionospheric disturbances (TIDs) caused by gravity wave (GW) propagation could have likely played a significant role in causing the phenomenon.

Description: Published

Description: A12314

Description: 1.6. Osservazioni di geomagnetismo

Description: 1.7. Osservazioni di alta e media atmosfera

Description: 3.9. Fisica della magnetosfera, ionosfera e meteorologia spaziale

Description: 5.4. Banche dati di geomagnetismo, aeronomia, clima e ambiente

Description: JCR Journal

Description: open

Description: This paper describes how the joint utilization of autoscaled data such as the F2 peak critical frequency foF2, the propagation factor M(3000)F2 and the electron density profile, coming from two reference ionospheric stations (Rome and Gibilmanna), the regional (SIRMUP) and global (IRI) ionospheric models, can provide a valid tool for obtaining a real-time three-dimensional (3-D) electron density mapping of the ionosphere. Preliminary results of the proposed 3-D model are shown by comparing the electron density profiles given by the model with the ones measured at three testing ionospheric stations (Athens, Roquetes and S.Vito).

Description: Published

Description: RS5009

Description: 1.7. Osservazioni di alta e media atmosfera

Description: 3.9. Fisica della magnetosfera, ionosfera e meteorologia spaziale

Description: JCR Journal

Description: open

Description: Radar technology has for a long time used various systems that allow detection under high-resolution conditions, while emitting at the same time low peak power. Among these systems, transmitted pulse encoding by means of biphasic codes has been used for the advanced ionospheric sounder that was developed by the AIS-INGV ionosonde. In the receiving process, suitable decoding of the signal must be accomplished. This can be achieved in both the time and the frequency domains. Focusing on the time domain, different approaches are possible. In this study, two of these approaches have been compared, using data acquired by the AIS-INGV and processed by means of software tools (mainly Mathcad©). The analysis reveals the differences under both noiseless and noisy conditions, although this does not allow the conclusive establishment as to which method is better, as each of them has benefits and drawbacks.

Description: Published

Description: 1-11

Description: 1.7. Osservazioni di alta e media atmosfera

Description: JCR Journal

Description: open

Description: We reply to a comment by Messina et al., who strongly criticized our paper on the San Pio Fault, by showing that in areas of complex geology such as the central Apennines, where the current tectonic setting results from the superposition of different tectonic regimes, the equation: “most visible active fault = major seismogenic fault” can be misleading.

Description: Published

Description: 421-423

Description: 3.2. Tettonica attiva

Description: JCR Journal

Description: restricted

Description: Il Centro di Ricerche Sismologiche (CRS) dell’Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - OGS è stato istituito con la legge n. 399 del 30 novembre 1989 col fine istituzionale di: “...svolgere, in autonomia scientifica e secondo specifici progetti: ricerche sulla sismicità e sulla sismogenesi dell’Italia nordorientale, gestendo e sviluppando inoltre la connessa rete di rilevamento sismico anche per fini di protezione civile. Nei campi di sua competenza il dipartimento svolge inoltre: attività applicativa; studi e ricerche sulle tecnologie di acquisizione, trasmissione e trattamento del segnale sismico; studi e ricerche per l’affinamento del modello sismotettonico dell’Italia nord-orientale.” Dal 2003, in seguito alla conferenza “Integrating the Seismic Monitoring in Central Europe” tenutasi a Udine e al Workshop “Beyond Frontiers: Seismic Networks in the Southern Alps” organizzato a Trieste, l’OGS ha partecipato al progetto europeo Interreg IIIa Italia/Austria “Reti sismologiche senza frontiere nelle Alpi sudorientali” 1. Il progetto nasce dalla stretta collaborazione esistente tra: • il CRS dell’OGS a Udine; • la Protezione Civile della Regione Friuli-Venezia Giulia (FVG); • l’allora Dipartimento di Scienze della Terra (DST) dell’Università di Trieste (adesso Dipartimento di Geoscienze); • lo Zentralanstalt für Meteorologie und Geodynamik, Hauptabteilung Geophysik di Vienna in Austria (ZAMG); • l’Urad za seizmologijo, geologijo, Agencija Republike Slovenije za okolje, di Lubiana in Slovenia (ARSO). Il terremoto di Bovec, avvenuto in prossimità dei confini tra FVG, Carinzia e Slovenia nel 1998, ha evidenziato l’importanza di un’integrazione e potenziamento delle reti delle diverse nazioni. In particolare, in tale occasione si è evidenziato: l’eterogeneità della strumentazione esistente nelle diverse reti, la mancanza di connessione dedicata tra i centri sismologici anche all’interno della stessa nazione e la mancanza di un sistema di elaborazione ed archiviazione dei dati omogeneo. Lo scopo del progetto è stato quindi l’integrazione transfrontaliera delle reti sismologiche presenti nelle tre nazioni per far fronte alle necessità di protezione civile e per scopi di ricerca scientifica. La disponibilità in tempo reale di forme d’onda dei terremoti permette, infatti, l’analisi immediata dei dati in maniera automatica che fornisce informazioni rapide ed affidabili alle autorità di protezione civile. Gli obiettivi principali raggiunti durante il progetto sono: 1. la creazione di un centro di raccolta dati in tempo reale presso la Sala Operativa Regionale (SOR) di Palmanova della Protezione Civile del Friuli-Venezia Giulia e l’adattamento dei centri raccolta dati del DST, dell’OGS e di Vienna a questi scopi. La duplicazione dei centri di raccolta dati e delle connessioni tra questi garantisce il funzionamento del sistema anche nel caso che uno o più centri siano fuori uso per i danni subiti da un sisma distruttivo; 2. l’individuazione e la realizzazione di uno o più sistemi di connessione dati efficienti e sicuri tra le stazioni ed i centri di raccolta; 3. la ridefinizione della geometria attuale delle reti, in funzione della migliore copertura possibile delle aree potenzialmente pericolose a ridosso dei confini di stato; 4. la programmazione dei protocolli comuni d’intervento in caso di forti terremoti.

Description: Published

Description: 38-41

Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale

Description: N/A or not JCR

Description: open

Description: After an earthquake, rapid, real-time assessment of hazards such as ground shaking and tsunami potential is important for early warning and emergency response. Tsunami potential depends on sea floor displacement, which is related to the length, L, width, W, mean slip, D, and depth, z, of earthquake rupture. Currently, the primary discriminant for tsunami potential is the centroid-moment tensor magnitude, MwCMT, representing the seismic potency LWD, and estimated through an indirect, inversion procedure. The obtained MwCMT and the implied LWD value vary with the depth of faulting, assumed earth model and other factors, and is only available 30 min or more after an earthquake. The use of more direct procedures for hazard assessment, when available, could avoid these problems and aid in effective early warning. Here we present a direct procedure for rapid assessment of earthquake tsunami potential using two, simple measures on P-wave seismograms – the dominant period on the velocity records, Td, and the likelihood that the high-frequency, apparent rupture-duration, T0, exceeds 50-55 sec. T0 can be related to the critical parameters L and z, while Td may be related to W, D or z. For a set of recent, large earthquakes, we show that the period-duration product TdT0 gives more information on tsunami impact and size than MwCMT and other currently used discriminants. All discriminants have difficulty in assessing the tsunami potential for oceanic strike-slip and back-arc or upper-plate, intraplate earthquake types. Our analysis and results suggest that tsunami potential is not directly related to the potency LWD from the “seismic” faulting model, as is assumed with the use of the MwCMT discriminant. Instead, knowledge of rupture length, L, and depth, z, alone can constrain well the tsunami potential of an earthquake, with explicit determination of fault width, W, and slip, D, being of secondary importance. With available real-time seismogram data, rapid calculation of the direct, period- duration discriminant can be completed within 6-10 min after an earthquake occurs and thus can aid in effective and reliable tsunami early warning.

Description: In press

Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale

Description: JCR Journal

Description: open

Description: The aim of this study is the sharing of waveforms recorded by several Istituto Nazionale di Geofisica e Vulcanologia (INGV) temporary stations (managed by the Milan-Pavia section; INGV MI-PV). These stations were installed after the April 6, 2009, Mw 6.3, L'Aquila earthquake (central Italy). The work synthesizes the activities conducted in the field by the INGV MI-PV working group over the three months following the mainshock. The field activities were developed in four different phases that were defined according to their time periods. Starting from April 7, 2009, for the first phase, the temporary stations were installed in correspondence with the more damaged areas. The scope was to record the strongest aftershocks in the days that followed the mainshock. In this phase, the stations were composed of a sixcomponent acquisition system that was coupled with both a weak-motion and a strong-motion sensor. After the first month, the last three phases of installation investigated the seismic responses of sites located in the epicentral area, involving villages within a radius of about 20 km from the epicenter of the April 6 mainshock. In this way, over four specific time-period phases, the stations were installed in sites with different lithological and geomorphological conditions. The instruments worked from April 7 to July 14, 2009; in this period, 9,155 aftershocks (134,262 accelerometric waveforms and 133,242 velocimetric waveforms), with ML ≤5.3 were recorded. This study describes the dataset of these earthquake waveforms recorded with both velocity and acceleration transducers. Selected waveforms are available through ftp://ftp.mi.ingv.it/download/RAIS-TS_rel01/, with their corresponding information concerning instrumental characteristics, installation sites, and earthquakes recorded.

Description: Published

Description: 101-113

Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale

Description: JCR Journal

Description: open

Description: The elevation of the Capo Vaticano coastal terraces (Tyrrhenian coast, central Calabria) is the combination of regional uplift and repeated coseismic displacement. We subtract the regional uplift from the total uplift (maximum average uplift rates 0.81-0.97 mm/yr since ~0.7 Ma) and obtain a residual fault-related displacement. Then, we model the residual displacement to provide constraints to the location and geometry of the seismogenic source of the 1905 M7 earthquake, the strongest – and still poorly understood – earthquake of the instrumental era in this area. We test four different potential sources for the dislocation modelling and find that 1) three sources are not compatible with the displacement observed along the terraces, and 2) the only source consistent with the local deformation is the 100°-striking Coccorino Fault. We calculate average long-term vertical slip rates of 0.2-0.3 mm/yr on the Coccorino Fault and estimate an average recurrence time of ~one millennium for a 1905-type earthquake

Description: Published

Description: 378-389

Description: 3.2. Tettonica attiva

Description: JCR Journal

Description: reserved

Description: Il 6 Aprile 2009 un terremoto di Ml=5.8 (Mw=6.2) ha colpito L’Aquila e la media valle dell’Aterno in Abruzzo. In questo lavoro presentiamo in maniera sintetica i rilievi geologici effettuati in campagna dal gruppo di lavoro EmerGeo a seguito della sequenza sismica aquilana. Le attività di rilevamento condotte sono consistite principalmente nella verifica, definizione e caratterizzazione delle deformazioni cosismiche superficiali osservate lungo le strutture tettoniche note in letteratura; sono stati inoltre rilevati e riportati altri effetti cosismici locali (fratture su asfalto, frane e scivolamenti) non direttamente collegati alla presenza di strutture tettoniche. In totale sono stati rilevati oltre 300 punti di osservazione su una porzione di territorio estesa circa 900 km2. L’analisi preliminare dei rilievi effettuati indica che le rotture osservate lungo la faglia di Paganica, per la continuità e le caratteristiche, rappresentano l’espressione superficiale della faglia responsabile dell’evento del 6 aprile 2009, e che le rotture lungo le faglie di Bazzano e di Monticchio-Fossa possono rappresentare l’espressione in superficie di una struttura antitetica riattivata durante l’evento.

Description: Published

Description: 1-79

Description: 3.2. Tettonica attiva

Description: N/A or not JCR

Description: open

Description: Rapid extension and active normal faulting in the western extremity of the Corinth Gulf are accompanied by fast coastal uplift.We investigate Pleistocene uplift west of Aigion, by attempting to date remains of marine terraces and sedimentary sequences by calcareous nannoplankton and U-series analyses. Net uplift initiated recently, due to abandonment of an older rift-bounding fault zone and increase in activity on the presently active, coastal fault zone. This change apparently coincides with an abrupt slow down (or, termination) of secondary fault block tilting within the broader hangingwall block of the older zone, indicated by an angular unconformity that dates in the early part ofMIS10 ( 390–350 ka BP, preferably, in the earlier part of this period). Net uplift driven by the coastal zone resulted in the formation of MIS9c (330 ka) and younger terraces. The formation of the unconformity and the initiation of net uplift coincide temporally with a 300–400 ka unconformity recognized by recent studies in a wide area offshore Aigion i.e. they could be part of an evolutionary event that affected the entirewestern part of the Corinth Rift or, a large area therein. Uplift rate estimates at four locations are discussed with reference to the morphotectonic context of differential uplift of secondary fault blocks, and the context of possible increase in uplift ratewith time. Themost reliable and most useful estimate for uplift rate at the longitude of the studied transect is 1.74–1.85mm/year (time-averaged estimate for the last 240 ka, based on calcareous nannoplankton and sequence-stratigraphic interpretation)

Description: ‘3HAZ Corinth’ E.U. research project 004043 (GOCE)-3HAZ-Corinth

Description: Published

Description: 78 - 104

Description: 3.2. Tettonica attiva

Description: JCR Journal

Description: partially_open

Description: A seismic noise recording experiment has been carried out in the Campi Flegrei volcanic area from March 9 to 26, 2009 in the framework of the INGV-DPC 2007-2009 agreement (Project V1 – UNREST). The project aimed at the realization of an integrated method for the definition of the unrest phases at Campi Flegrei. 21 digital three-component seismic stations equipped with broad band seismometers have been added to the existing 11 digital stations already deployed in the area. The preliminary results show a correlation between the seismic noise level and the anthropic activity, whereas the meteorological conditions seem affecting the low frequency seismic noise. These results are important to define the detection thresholds of the seismic signals generated during a possible renewal phase of the volcanic activity.

Description: Published

Description: 1-21

Description: N/A or not JCR

Description: open

Description: The experience acquired from more than ten years of operation of an Antarctic geomagnetic observatory is described along with the development of data transmission facilities. The observatory was deployed at the Spanish Antarctic Station in 1996. The main instrument was an Overhauser magnetometer deployed in dual axis Helmholtz coils, a δD/δI configuration. The site is only manned during the summer, with the magnetometer left recording throughout the rest of the year. During the 2007-2008 survey the observatory instrumentation has been upgraded with a DMI suspended triaxial fluxgate magnetometer, new sampling hardware and data logging software. Both sampling and timing are carried out under the control of a PIC based microcontroller and GPS receiver. Data presentation, transmission and archiving are performed under the control of a low power embedded PC. For real time access to the data two options have been provided and rigorously tested during the last 10 years: METEOSAT and GOES Data Collection Systems, and recently, a high frequency (HF) digital radio-link, using ionospheric propagation between Antarctica and Spain, has been developed. This latest transmission system is being continuously upgraded, and it would be possible to extend its application to other remote stations. Measurements have been made during the last four years in order to determine the channel characteristics and its variability, mainly the multipath and Doppler spread and the link availability for a given SNR in the receiver. These measurements are being used to design the physical layer of a radiomodem intended to maximize the link capacity keeping the emitted power low.

Description: Published

Description: 45-56

Description: 1.6. Osservazioni di geomagnetismo

Description: 2.6. TTC - Laboratorio di gravimetria, magnetismo ed elettromagnetismo in aree attive

Description: JCR Journal

Description: open

Description: Questa nota presenta una sintesi delle attività svolte durante il rilievomacrosismico del terremoto avvenuto tra le province di Parma e Reggio Emilia il 23 dicembre 2008. La scossa di Ml 5.2 è stata localizzata a sud di Parma ed è stata avvertita in tutta l’Italia settentrionale e in gran parte della Liguria e della Toscana. Il presente rapporto illustra lemodalità di intervento del teamQUEST, relative al rilievo degli effetti e alla valutazione in intensità MCS in particolare per le località della zona epicentrale. L’ampia documentazione fotografica illustra alcuni dettagli delle tipologie di danneggiamento rilevate e consente di comprendere meglio le valutazioni dell’intensità macrosismica. This paper presents an overview of the activities performed during the macroseismic field survey of the earthquake that occurred in the Parma and Reggio Emilia region on December 23, 2008. The mainshock (Ml=5.2), was located south of the city of Parma and was resolutely felt through Northern Italy. The report here presented shows the procedures carried out by QUEST (Quick Earthquake Survey Team), concerning the survey. QUEST has been engaged in gathering the damage information and in assessing the macroseismic intensity, in particular about the epicentral area. A copious photo collection shows details of the observed damage nature and allows to better illustrate the intensity

Description: Published

Description: 1-41

Description: 5.1. TTC - Banche dati e metodi macrosismici

Description: N/A or not JCR

Description: open

Description: This review paper presents the main achievements of the near Earth space plasma monitoring under COST 296 Action. The outputs of the COST 296 community making data, historical and real-time, standardized and available to the ionospheric community for their research, applications and modeling purposes are presented. The contribution of COST 296 with the added value of the validated data made possible a trusted ionospheric monitoring for research and modeling purposes, and it served for testing and improving the algorithms producing real-time data and providing data users measurement uncertainties. These value added data also served for calibration and validation of space-borne sensors. New techniques and parameters have been developed for monitoring the near Earth space plasma, as time dependent 2D maps of vertical total electron content (vTEC), other key ionospheric parameters and activity indices for distinguishing disturbed ionospheric conditions, as well as a technique for improving the discrepancies of different mapping services. The dissemination of the above products has been developed by COST 296 participants throughout the websites making them available on-line for real-time applications.

Description: Published

Description: 221-234

Description: 1.7. Osservazioni di alta e media atmosfera

Description: 3.9. Fisica della magnetosfera, ionosfera e meteorologia spaziale

Description: 5.4. Banche dati di geomagnetismo, aeronomia, clima e ambiente

Description: JCR Journal

Description: open

Description: Seismic monitoring in Italy has strongly improved since the 1997 Umbria-Marche earthquake sequence. This has made the National Seismic Network (RSN) a powerful tool both to rapidly locate and quantify thousands of earthquakes occurring in Italy every year, and to study the seismic activity in detail, accumulating an impressive high quality data set that will be exploited in the coming years to understand earthquake processes and to investigate the deep structure. This paper summarizes and compares the basic features of the seismicity recorded in 2000 and 2006, before and after the implementation of the new RSN, showing that the number of well located earthquakes has more than doubled and that the completeness magnitude has dropped from ~2.3 to ~1.7. In addition, we concentrate on the evaluation of the current automatic location and magnitudes versus the revised ones, published routinely in the INGV bulletins. We show that the rapid estimates of locations and magnitudes are robust and reliable for most regions in Italy: more than 75% of the earthquakes are located in real time within 10km from the «true» locations, whereas the rapid magnitudes ML are within ±0.4 from the revised values in 90% of cases. The comparison between real-time and revised locations shows that there are a few regions in Italy where a further network improvement is still desirable. These include all the off-shore regions, Calabria, western Sicily, the Alpine and Po Plain region, and some small areas along the peninsula.

Description: Published

Description: 417-431

Description: 5.2. TTC - Banche dati di sismologia strumentale

Description: JCR Journal

Description: open

Description: In 2007 several events were organized to celebrate the fiftieth anniversary of the International Geophysical Year (IGY, 1957-1958). The celebrations will last until 2009 and are taking place within different contexts: the International Polar Year (IPY), the International Heliophysical Year (IHY), the electronic Geophysical Year (eGY) and the International Year of Planet Earth (IYPE). IGY offered a very appropriate and timely occasion to undertake a series of coordinated observations of various geophysical phenomena all over the globe. Italy took part in the broad international effort stimulated by IGY. In fact, Italy participated in observations and studies in many of the proposed scientific areas, in particular Geomagnetism and Aeronomy. The Istituto Nazionale di Geofisica (ING) started the installation of observatories, and updated and ensured continuous recording of geophysical observations. Geomagnetism, ionospheric physics, seismology, and other geophysical disciplines, were advanced. Although much of the work was undertaken in Italy, some attention was also devoted to other areas of the world, in particular Antarctica, where Italy participated in seismological observations. This paper gives a summary of the Geomagnetism and Ionospheric Physics activities within IGY. Furthermore, we highlight the importance of this historical event and its outcomes for the improvement of geophysical observations and the post-IGY growth of scientific investigations in Italy.

Description: Published

Description: 127 - 135

Description: 1.6. Osservazioni di geomagnetismo

Description: 1.7. Osservazioni di alta e media atmosfera

Description: 3.9. Fisica della magnetosfera, ionosfera e meteorologia spaziale

Description: JCR Journal

Description: open

Description: Questo lavoro presenta una utility per il GIS MapInfo™ sviluppata per l'archiviazione ed elaborazione dei dati macrosismici dalla fase di georeferenziazione fino al plottaggio finale su mappa. L'identificazione della località associata con un'osservazione macrosismica è un'operazione che talvolta può causare errori ed in seguito problemi nell'analisi ed interpretazione dei dati. La routine MacroMap fornisce uno strumento che in modo semplice e veloce aiuti nell'identificazione della corretta località a cui attribuire l'informazione macrosismica durante lo studio di un terremoto. L'utility è strutturata per utilizzare il formato della directory geografica DIR04 e le procedure adottate nella compilazione del DataBase Macrosismico Italiano DBMI04. MacroMap è stata sperimentata "sul campo" durante alcune indagini macrosismiche e tiene conto dell'esperienza e dei suggerimenti degli operatori del Gruppo QUEST (QUick Earthquake Survey Team). I campi di utilizzo di MacroMap vanno dalla realizzazione speditiva di mappe e tabelle per la produzione di report macrosismici per la Protezione Civile, alla revisione di terremoti storici, grazie all'avanzato sistema di query disponibile per la selezione dei toponimi del database geografico.

Description: Published

Description: 1-21

Description: 5.1. TTC - Banche dati e metodi macrosismici

Description: N/A or not JCR

Description: open

Description: Two layers of fine sand of marine origin occur in a sequence of organic rich colluvia in an archaeological excavation at Torre degli Inglesi, on Capo Peloro, northeast Sicily. Stratigraphic and micropaleontologic analyses support the hypothesis that these layers are related to deposition due to paleotsunami waves. Their ages are constrained both with radiocarbon and archaeological datings. The age of the oldest layer is coincident with the 17 A.D. earthquake that hit Reggio Calabria but for which no tsunami was previously reported. The age of the youngest layer can be only constrained in the range 3rd– 19th century and is tentatively associated to the 6 Feb. 1783 event.

Description: Italian Civil Protection Department in the frame of the 2004 – 2006 agreement with Istituto Nazionale di Geofisica e Vulcanologia – INGV (Seismological Project S2) and E.C. project TRANSFER (contract 037058)

Description: Published

Description: L05311

Description: 3.2. Tettonica attiva

Description: JCR Journal

Description: partially_open

Description: At the westernmost part of the Corinth Rift (Greece), an area of rapid extension and active normal faulting, geomorphological observations reveal the existence and geometry of an active NW-SE trending coastal fault system, which includes the Aigion fault. We recognize a similar fault pattern on both the coastal range front to the NW of Aigion town and the Holocene fan deltas in front of it. We interpret this as a result of recent migration of faulting to the hanging wall of the fault system. Differences in the geomorphic expression of the constituent faults provide hints on the possible evolution of the fault pattern during this recent migration. A trench excavated across one of the identified coastal fault scarps (on a Holocene fan delta) provides information on the seismic history of the fault system, which includes at least four (possibly six) earthquakes in the past 4000 years. A minimum estimate for the slip rate of the trenched fault is 1.9–2.7 mm/yr. The trench exposed sediments of an uplifted paleolagoon (approximate age 2000 years B.P.), inside which the last two earthquakes formed an underwater monoclinal scarp. Oscillating coastal vertical movements are suggested by the fact that the lagoonal deposits are also uplifted on the trenched fault hanging wall (uplift by offshore faults) and by the abrupt transition from fluvial to lagoonal deposits (subsidence by more landward faults, assuming that extensive coastal sediment failure has not taken place in the specific part of the fan delta, within the time interval of interest). These movements suggest that the proposed migration of activity from the range front faults to those on the fan deltas is probably still ongoing, with activity on both sets of faults.

Description: Published

Description: B09302

Description: 3.2. Tettonica attiva

Description: JCR Journal

Description: reserved

Description: During local and regional earthquakes, an evident amplification of horizontal ground motion is observed at two seismological stations near the Tremestieri fault, on the southeastern flank of Mt. Etna volcano. Rotated-component spectral ratios show a narrow spectral peak around 4-Hz along a N40°E direction. A conventional polarization analysis using the eigenvectors of the covariance matrix confirms the very stable directional effect enhancing the approximately NE-SW elongation of the horizontal ground motion in the fault zone. The effect is evident during the entire seismogram and independent of source backazimuth as well as distance and depth of earthquakes. The same polarization is observed in ambient noise as well. This consistency allowed us to use microtremors for checking ground motion polarization along and across the Tremestieri fault zone with a high spatial resolution. The result is a stable polarization of horizontal motion in the entire area, interesting a broad frequency band. To check whether this ground motion property is recurrent and understand a possible relationship with fault strike, faulting style, or orientation of fractures, ambient noise was recorded on other mapped faults of the Mt. Etna area, the Moscarello, Acicatena and Pernicana faults. The latter, in particular, is characterized by different strike and faulting style. A systematic tendency of ambient noise to be polarized is found in all of the faults. A picture emerges where normal faults of the eastern flank show a E-W to NE-SW polarization that changes on the Pernicana fault, which develops approximately E-W and is characterized by a prevailing NW-SE to NS polarization. Directions of polarization were never parallel to the fault strike. Moreover, polarization persists too far away from the fault trace, excluding an effect limited to a narrow low velocity zone hosted between harder wall rocks. Both these observations rule out an interpretation in terms of fault-trapped waves. The cause of observed polarizations will be the subject of future studies. However, the consistency with recent results of velocity anisotropy in a part of the investigated area suggests a possible role of attenuation anisotropy on horizontal amplitude variations versus azimuth.

Description: Published

Description: B10306

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: JCR Journal

Description: open

Description: This work describes a method that has been developed to automatically assess whether the F1 layer is present or not on an ionogram trace, and, if present, to scale the F1 critical frequency foF1. The ionograms in which the information related to the F1 trace is insufficient are identified and considered separately. In order to test the performance of this method and the conditions in relation to which it could be improved, a data set of ionograms recorded from September 2005 to June 2006 by the AIS-INGV ionosonde installed at Rome was used. The values obtained automatically by Autoscala, with the addition of this new F1 layer routine, were compared with those obtained by the standard manual method.

Description: Published

Description: RS2S91

Description: 1.7. Osservazioni di alta e media atmosfera

Description: 3.9. Fisica della magnetosfera, ionosfera e meteorologia spaziale

Description: JCR Journal

Description: reserved

Description: The 12 November 1999 Mw 7.1 earthquake ruptured the Du¨zce segment of the North Anatolian Fault Zone and produced a 40-km-long surface rupture. To improve knowledge about earthquake recurrence on this fault, we undertook paleoseismological trench investigations. We found evidence for repeated surface faulting paleoearthquakes predating the 1999 event during the past millennium. Dating was based on radiocarbon, 210Pb analyses, and archaeological considerations. In addition to the 1999 earthquake, prior surface faulting earthquakes are dated as follows: A.D. 1685–1900 (possibly end of 19th century), A.D. 1495–1700, and A.D. 685–1020 (possibly A.D. 890–1020). The A.D. 967 and A.D. 1878 historical earthquakes are good candidates to have ruptured the Du¨zce fault correlating with the oldest and penultimate paleoearthquakes. No obvious correlation for the third paleoearthquake (A.D. 1495–1700) exists. These results shows that the Du¨zce fault considerably participates, along with the parallel Mudurnu fault sections, in the seismogenic deformation taking place along this part of the North Anatolian Fault. Four events since A.D. 685–1020 (possibly A.D. 890–1020) would yield an average recurrence time for the Du¨zce fault of 330–430 years (possibly 330– 370 years). The three most recent earthquakes, including 1999, occurred within 500 years. Merging results from other paleoseismological studies along the Du¨zce fault show a consistency of results and yields average recurrence times for the past 2000 years of 320– 390 years. Assuming that the 1999 slip (2.7 m average, 5 m maximum) is representative of the behavior of this fault, the above recurrence times yield a reference figure of fault slip rate in the range 6.9–15.6 mm/a

Description: EU project RELIEF (EVG1-CT-2002-00069)

Description: Published

Description: B01309

Description: 3.2. Tettonica attiva

Description: JCR Journal

Description: reserved

Description: The spatial pattern of the b value of the frequency-magnitude relation has been analyzed using gridding techniques beneath Mount Etna, Italy. A regional data set of 2900 events with Md (duration magnitude) 1.5 up to 15 km depth occurring between August 1999 and December 2005 has been used. Two regions with an abnormally high b value have been found, one centered beneath the southern part of the Valle del Bove, above the 6 km below sea level (bsl) deep basement, and the other beneath the summit region 2 km bsl east of the Central Craters. We can infer that these high b value anomalies are regions of increased crack density, and/or high pore pressure, related to the presence of nearby magma storage. This interpretation is supported by all the available geophysical evidence, such as tomographic studies and geodetic deformation measurements. The data set has also been subdivided into five periods, corresponding to different phases of volcanic activity: 2001 preeruption, 2001 eruptive, 2002–2003 preeruption, 2002–2003 eruptive, and 2002–2003 posteruption. The minimum magnitude of completeness, Mc, and the b value were computed for each period. A volume of anomalously high b values can be observed in each of these periods (except for the 2002–2003 preeruption interval). This approach has allowed the detection of the transient presence of magmatic intrusions during the various periods evaluated.

Description: Published

Description: B12303

Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive

Description: 4.3. TTC - Scenari di pericolosità vulcanica

Description: JCR Journal

Description: reserved

Description: We present paleoseismological trenching results for the active Skinos Fault, which ruptured the surface on the Alkyonides Gulf basin margin in the 1981 Gulf of Corinth earthquake sequence. Three trenches expose evidence of up to six previous events which are comparable to the 1981 deformation in terms of size and geometry. Vertical displacement produced by the 1981 earthquake ranged from 0.45 to 1.3 m at the Bambakies Fan trench sites, decreasing towards the eastern fault tip east of the trenches. Trench 1 reveals two previous events with vertical displacements between 0.5 and 1.2 m since 390 A.D. Trench 2 reveals five or six previous events, but these are not dated. Trench 3 reveals four previous events since 670 A.D. Vertical displacements associated with interpreted paleoearthquakes at the trench sites are ≤1.2 m. The recurrence interval on the Skinos Fault is estimated to average 330 years. However, significant variation in recurrence interval is allowed by the available radiometric dates. Average vertical displacement rates derived from the trenches are in the range 0.7-2.5 mm/yr. A similar long-term average vertical displacement rate of 1.2-2.3 mm/yr is estimated for the lifespan of the basin-bounding fault. This equates to a horizontal seismic strain contribution of ≤2.5 mm/yr from the Skinos Fault. This local seismic strain rate overlaps, within error, with geodetically determined velocities across the Alkyonides Gulf assumed to represent uniform deep-crustal strain. Thus seismic deformation on the basin-bounding fault system may take up the major part of extension across the basin, and aseismic strain is not necessitated by the data. If correct, this would imply that geodetically determined strain rates may be used as a proxy for potential seismic moment release in seismic hazard analyses for this region.

Description: Published

Description: 30,001-30,019

Description: 3.2. Tettonica attiva

Description: N/A or not JCR

Description: reserved

Description: We report unprecedented observations of long-period (LP) seismicity in non-volcanic setting. Our data are from the Central-Northern sector of the Apennine chain, Italy. For this area, intense CO2 circulation of mantle origin has been documented by either groundwater composition and borehole measurements. We perform waveform correlation and stacking to obtain reliable epicenter estimates. Following Chouet's crack model, we find that both the quality factor and dominant frequency of LP oscillations are consistent with the sustained resonance of a wet crack filled by a water-CO2 mixture.

Description: Published

Description: L12303

Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale

Description: JCR Journal

Description: reserved

Description: The Umbria-Marche sequence represents the first case in Italy for which the surface effects of a moderate seismic event (5〈M〈6) were systematically investigated and documented. Surface fractures attributed to the events were mapped by several groups of researchers. The coseismic features were expressed mainly by NW-SE trending, discontinuous, linear open fractures, as well as fracture swarms, locally with centimetric vertical displacements. They affected rocks and loose deposits, buildings, and roads. Because of the earthquake sizes (M≤6), the deformation was faint, making the detection difficult and giving rise to different seismotectonic interpretations: specifically, surface rupture of the seismogenic fault, triggered slip on secondary faults, and shaking-induced sliding of debris. Consequently, different models of connection between surface offsets and displacements at depth were proposed that integrated geology with other geophysical data. However, whether direct or indirect expression of the deep dislocation, the geometry of these fractures reflected the seismogenic structure. Even in the case of these moderate-earthquakes features, geomorphical and paleoseismological studies provide data for reconstructing the recent tectonic evolution of the region and for determining the frequency and size of earthquakes. Finally, we learned a more efficient way to prepare for post-earthquake emergency response, particularly for long-lasting sequences in highly vulnerable built environments, such as the ancient villages within the Apennines.

Description: Published

Description: 361-381

Description: 3.2. Tettonica attiva

Description: JCR Journal

Description: open

Description: This paper focuses on the problem of invalid O/X polarization tagging of an ionogram and how this can affect ionogram autoscaling methods. To illustrate this problem, 623 ionograms recorded in March and April 2004 (days 080-105) by the digisonde 256 installed at Learmonth (22.3° S, 114.1° E) were considered. These ionograms, often characterized by very unreliable O/X polarization tagging of the echoes because of unresolved antenna issues, have been autoscaled by both ARTIST 4.2 and Autoscala. Results of comparisons between automatically and manually scaled foF2 data are shown for both programs, considering as acceptable an autoscaled value that lies within 0.5 MHz of the manual value. Autoscala values of foF2 agree with the manually-scaled values for ~99% of ionograms, while ARTIST values of foF2 agree with the manually-scaled values for ~75% of ionograms. While ARTIST was coded on the assumption of valid polarization tagging, the fact remains that it produces invalid results when equipment issues cause invalid tagging. Autoscaling procedures that do not use the polarization tagging will generally work better than ARTIST in such cases. However, these other procedures are susceptible to failure in other situations.

Description: Published

Description: 597-607

Description: 1.7. Osservazioni di alta e media atmosfera

Description: 3.9. Fisica della magnetosfera, ionosfera e meteorologia spaziale

Description: JCR Journal

Description: open

Description: The modern digital seismic stations are provided with 24 bit A/D converters, high capacity recording systems and broad-band seismometers. Nevertheless, few tens year old seismic stations can be still able to give an useful contribution to seismic monitoring. Some out-of-date seismic stations, such as the Lennartz PCM 5800, are characterized by the data acquisition in trigger mode on magnetic tape, allowing a continuous recording time of about 90 minutes. We have checked the possibility to substitute the Uher tape recorder of the Lennartz PCM 5800 stations with modern digital recorder, in order to give a new life to these stations. Several type of digital recorders have been tried. According to the results of our trials, the Hi-MiniDisc (Hi-MD) recorder is resulted the most useful one. This apparatus records on 1GB magneto-optical disks with a continuous recording time up to about 8 hours. This time allows to record about 500 trigger windows of about 50-60 seconds on one disk, about 5 time the old magnetic tape. According with these results, the Lennartz PCM 5800 digital seismic stations can be useful during seismic experiments or as a support of the Permanent Seismic Networks at local and regional scale.

Description: Published

Description: 1-17

Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive

Description: N/A or not JCR

Description: open

Description: A method for automatic scaling of the maximum frequency and virtual height of a sporadic E layer is presented. A set of ionograms recorded at the ionospheric observatory of Gibilmanna was used to test the performance of the algorithm. The test was performed by comparing the data obtained automatically with the values scaled by an operator.

Description: Published

Description: RS2012

Description: 1.7. Osservazioni di aeronomia

Description: 3.9. Fisica della magnetosfera, ionosfera e meteorologia spaziale

Description: JCR Journal

Description: reserved

Description: We detect seismic wave velocity changes at Mt. Vesuvius, using doublets and the Coda Wave Interferometry method. The high sensitivity of multiply scattered coda waves to temporal changes in the medium allows us to detect velocity variation smaller than 0.4%. We use 17 doublets, some of them grouped in families of multiplets, spanning January 1996 to December 1999. Data show a systematic increase in velocity from 1996 to end- September 1999, followed by a rapid drop in velocity. This drop immediately precedes a sustained swarm of VT-type earthquakes, including the 9th October 1999 M = 3.6 event, the largest in the region since at least 1972. We propose a long term fluid pressurization followed by influx as a possible causative mechanism.

Description: Published

Description: L06306

Description: reserved

Description: The Institute for Geophysics at Hamburg University and the Research Center for Marine Geoscience (GEOMAR) of Kiel University have developed new, wideband ocean bottom seismic stations for long-term, deep sea deplyments of up to 1 year.

Description: Published

Description: 309-315

Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive

Description: open

Description: The performances of Autoscala and ARTIST 4.5 were comparatively evaluated using a large database of 6098 ionograms recorded from September 2005 to June 2006 by the digisonde DPS4 at the Rome ionospheric station. Results of comparisons between automatically and manually scaled data are shown for both programs highlighting the different behaviours. The Autoscala and ARTIST 4.5 values of foF2 and MUF(3000)F2 both agree with the hand-scaled values for ~95% of ionograms. For the other ~5% of ionograms, which the manual scaler classed as unscalable, ARTIST 4.5 usually gave invalid results, whereas Autoscala usually gave no result. The data recorded by the ionosondes DPS4 (interpreted by ARTIST 4.5) and AIS-INGV (interpreted by Autoscala) during 3 geomagnetic storms were also analysed. Ionograms with typical errors both for Autoscala and ARTIST 4.5 are displayed.

Description: Published

Description: RS4003

Description: 1.7. Osservazioni di aeronomia

Description: 3.9. Fisica della magnetosfera, ionosfera e meteorologia spaziale

Description: JCR Journal

Description: reserved

Description: Seismic networks are worldwide diffuse to monitor both volcanic and tectonic seismogenetic areas. Some differences, such the basement on which the seismometer is located and the environmental conditions, characterize the installation of seismic stations in volcanic and tectonic areas. Nevertheless, some basic principles are common. To obtain good quality seismic data is very important to realize a high grade installation of all the instruments equipping a seismic station. Several procedure must be taken into account to optimize the instrument setting up. Electronic noise may be minimize using proper connecting line and adequate grounding. Effective lightning protections are essential to save instruments from both surges and strikes. Good seismometer ground coupling improves the signal quality and the signal-to-noise ratio. These procedures have been carried out at the Osservatorio Vesuviano to improve the existing seismic network as well as the installation of the new stations. As a result of this action an improvement of both the signal-to-noise ratio and the network reliability has been obtained.

Description: Published

Description: 1-20

Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive

Description: open

Description: The NNE-trending Yangsan Fault (YSF) is the most prominent fault in the southeastern part of the Korean Peninsula and has a continuous trace about 200 km long. Activity on this fault was recently investigated using aerial photographs, topographic analysis, and trenching. The geomorphologic evidence of Late Quaternary faulting is clearly recognized on both the northern (Yugyeri and Tosung-ri areas) and southern parts (Eonyang to Tongdosa area) of the fault. The main YSF is marked by a zone of shattered rock that is tens of meters wide and zone of fault gouge. During the Late Quaternary, right-lateral movement occurred mainly on the southern part, as shown by lowangle striations on the fault plane, elongation of deformation features in the fault gouge. The estimated vertical slip rate is about 0.02-0.07 mm/yr, and the lateral slip rate may be several times larger than the vertical rate. The most recent event occurred prior to deposition of Holocene alluvium. In the northern part, the fault locally changes trend to almost N-S, dips to the east and has reverse movement. The average vertical slip rate is estimated less than 0.1 mm/yr. The most recent event probably occurred after 1314 cal. years BP (A.D. 536).

Description: Published

Description: JCR Journal

Description: open

Description: Although the Altyn Tagh Fault (ATF) is thought to play a key role in accommodating India-Eurasian convergence, little is known about its earthquake history. Studies of this strike-slip fault are important for interpretation of the role of faulting versus distributed deformation in the accommodation of the India- Eurasia collision. In addition, the 〉 1200 km long fault represents one of the most important and exemplary intracontinental strike-slip faults in the world. We mapped fault trace geometry and interpreted paleoseismic trench exposures to characterize the seismogenic behavior of the ATF. We identified 2 geometric segment boundaries in a 270 km long reach of the central ATF. These boundaries define the westernmost Wuzhunxiao, the Central Pingding, and the easternmost Xorxol (also written as Suekuli or Suo erkuli) segments. In this paper, we present the results from the Camel paleoseismic site along the Xorxol Segment at 91.759°E, 38.919°N. There evidence for the last two earthquakes is clear and 14C dates from layers exposed in the excavation bracket their ages. The most recent earthquake occurred between 1456 and 1775 cal A.D. and the penultimate event was between 60 and 980 cal A.D. Combining the Camel interpretations with our published results for the central ATF, we conclude that multiple earthquakes with shorter rupture lengths (?? 50 km) rather than complete rupture of the Xorxol Segment better explain the paleoseismic data. We found 2-3 earthquakes in the last 2-3 kyr. When coupled with typical amounts of slip per event (5-10 m), the recurrence times are tentatively consistent with 1-2 cm/yr slip rates. This result favors models that consider the broader distribution of collisional deformation, rather than those with northward motion of India into Asia absorbed along a few faults bounding rigid blocks.

Description: Published

Description: JCR Journal

Description: open

Description: Radio wave scintillations are rapid fluctuations in both amplitude and phase of signals propagating through the atmosphere. GPS signals can be affected by these disturbances which can lead to a complete loss of lock when the electron density strongly fluctuates around the background ionization level at small spatial scales. This paper will present recent improvements to the theoretical Global Ionospheric Scintillation Model (GISM), particularly tailored for satellite based navigation systems such GPS coupled with Satellite Based Augmentation System (SBAS). This model has been improved in order to take into account GPS constellation, signals, and receiver response to ionospheric scintillation environments. A new modelling technique, able to describe the scintillation derived modifications of transionospheric propagating fields is shown. Results from GPS derived experimental measurements performed at high and low magnetic latitudes will show preliminary assessments of the scintillation impact on real receivers and system operations. Nevertheless, comparisons between theoretical scintillation models, such as WBMOD and GISM, with GPS derived experimental data will be shown.

Description: Published

Description: JCR Journal

Description: open

Description: Amplitude scintillation data from GPS were analyzed. The objective is to estimate the impact of ionospheric scintillations at Satellite Based Augmentation Systems Ranging and Integrity Monitoring Station (SBAS RIMS) level and at GPS user level. For this purpose, a new approach to the problem was considered. Data were studied from the point of view of the impact of scintillations on the calculation of VTEC at pierce points and ionospheric grid points. An ionospheric grid of 5° 5° surface squares was assumed. From geometrical considerations and taking into account the basic principle to compute VTEC at grid points, with the data analyzed it is shown that scintillations very seldom affect the calculation of a grid point VTEC. Data from all the RIMS and for the entire GPS satellites network must be analyzed simultaneously to describe a realistic scenario for the impact of scintillations on SBAS. Finally, GPS scintillation data were analyzed at user level: service availability problems were encountered.

Description: Published

Description: JCR Journal

Description: open

Description: The North Tabriz Fault is a major seismogenic fault in NW Iran. The last damaging earthquakes on this fault occurred in 1721, rupturing the southeastern fault segment, and in 1780, rupturing the northwestern one. The understanding of the seismic behavior of this fault is critical for assessing the hazard in Tabriz, one of the major cities of Iran; the city suffered major damage in both the 1721 and 1780 events. Our study area is located on the northwestern fault segment, west of the city of Tabriz. We performed geomorphic and trenching investigations, which allowed us to recognize evidence for repeated faulting events since the Late Pleistocene. From the trenches, we found evidence for at least four events during the past 3.6 ka, the most recent one being the 1780 earthquake. On the basis of different approaches, horizontal slip per event and slip rates are found in the ranges of 4 ± 0.5 m and 3.1-6.4 mm/yr, respectively. We also attempted an estimate of the average recurrence intervals which appears to be in the range 350-1430 years, with a mean recurrence interval of 821 ± 176 years. On the basis of these results, the northwestern segment of the North Tabriz Fault does not appear to present a major seismic potential for the near future, however, not enough is known about the southeastern segment of the fault to make a comparable conclusion.

Description: Published

Description: JCR Journal

Description: open

Description: A preliminary validation of the technique developed using the NeQuick ionospheric model and the «effective ionization parameter» Az, based on vertical total electron content data ingestion, was carried out in a previous study. The current study was performed to extend the analyzed conditions and confirm the results. The method to validate this technique is based on a comparison between hourly F2 peak values measured with Vertical Incidence (VI) soundings and those calculated with the new technique. Data corresponding to different hours and seasons (equinox, summer solstice, and winter solstice) during the period 2000-2003 (high and medium solar activity conditions) were compared for all available ionosonde stations. The results show a good agreement between foF2 and hmF2 values obtained with the new technique and measurements from vertical incidence soundings during quiet and storms conditions.

Description: Published

Description: JCR Journal

Description: open

Description: A technique to reconstruct the electron density of the ionosphere starting from total electron content values has been developed using the NeQuick ionospheric electron density model driven by its effective ionization parameter Az. The technique is based on the computation of Az values for a suitable worldwide grid of points. A simple way to obtain relevant Az grids is to use global vertical Total Electron Content (TEC) maps to define for each grid point as Az value, the one that minimizes the difference between the experimental and the modeled vertical TEC. Having a global grid of Az values it is possible to compute the electron density at any point in the ionosphere using NeQuick. As a consequence, slant TEC values for specific ground station to satellite links or ionosphere peak parameter values at any location can be calculated. The results of the comparisons between experimental and reconstructed slant TEC as well as experimental and reconstructed peak parameters values indicate that the proposed reconstruction method can be used to reproduce the observed ionosphere in a realistic way.

Description: Published

Description: JCR Journal

Description: open

Description: Most GPS users employ low cost receivers. These receivers do not allow users to record the pseudorange that they observe, but the computed coordinates. This work presents an original and simple method to correct ionospheric biases introduced in GPS signals. The originality of this method is based on the fact that no pseudorange is needed to correct the biases, only the calculated coordinates are used. This distinguishes this method from other classic alternatives. This paper evaluates the efficiency of the method with the use of real data.

Description: Published

Description: JCR Journal

Description: open

Description: This paper shows the importance of the F1-layer shape in the electron density profiles obtained from ionograms with different inversion techniques when the profiles are used in ray tracing. This layer often controls the propagation on the path with ranges less than about 2000 km, particularly for spring and summer periods. Ionograms from two different stations, Hainan (19.4N, 109E) and El Arenosillo (37.1N, -6.7E), obtained during the month of July 2002 (average sunspot number: 99.6) during geomagnetic quiet conditions (Ap-index between 9 and 15) are analyzed. The profiles obtained with two different inversion techniques with different options are used together with the ray tracing program of the Proplab-Pro software. This program calculates the features of the received signal as angle of arrival, path length, height of reflection and range for each given profile assumed to define a spherically symmetric ionosphere in the region along the path. For each ionospheric condition (location, day, hour) the difference between range values obtained with Proplab-Pro program using profiles from the two techniques and the different options (POLAN no valley, POLAN valley, POLAN1-layer and NHPC) are considered.

Description: Published

Description: JCR Journal

Description: open

Description: HF-VHF radar techniques are easy to employ and commonly used in geophysical applications. They include deep radio soundings, used for probing the ionosphere, stratosphere-mesosphere measurement, weather forecast and radio-glaciology. Fast algorithms and powerful processors facilitate the development of several kinds of low power radars, but the reduction of the transmitted power has to be compensated by on-line processing of an encoded signal to maintain a favorable signal-to-noise ratio suitable for detection. Moreover, radars have to reconstruct return echoes with different travel times due to various origins (multi-path, adjacent objects, etc.). Such needs can be accomplished by means of signal phase coding and one of the most attractive is the reversal phase code. The composite echo signal must be processed to extract the physical information useful for the measurement considered. In this paper some algorithms used for on-line processing of phase-coded signals will be described, both in time and frequency domain.

Description: Published

Description: JCR Journal

Description: open

Description: The broad-band teleseismics records of the earthquake of October 29,1989 in Algeria (MW = 6.0) allow a detailed study of the rupture process of this earthquake. The focal mechanism obtained by P and SH modeling corresponds to reverse faulting with a small amount of left-lateral movement along a fault striking 246° and dipping 56°. The rupture is found to be complex with two sub-events separated in time but occurring on the same plane. The lowfrequency records of an accelerometer located some 25 km to the west of the main shock are also better fi tted when the rupture is composed of a double pulse. In the two cases, there is strong evidence for the rupture to propagate from south-west towards north-east.The relocalisation of the main shock by using a master-event technique and the data from Italian and Spanish stations led to the same conclusions. Soon after the main event, a temporary seimic network was installed in the epicentral area. The aftershock clouds defi ne a SW-NE fault dipping to the NW compatible with the results of the modelisations of the teleseismic body-waves and the accelerogram. The focal mechanisms correspond mainly to reverse faulting. The maximum principal direction of the stress tensor obtained from the inversion is about N-S and the minimum is vertical, typical of a compressive regime. The Chenoua earthquake took place on a fault which was not recognized as active. Repeated comparable seismic events on this fault and on the fault that borders the massif to the south explain this intriguing topographic feature.

Description: Published

Description: JCR Journal

Description: open

Description: Probabilistic seismic hazard analyses in Australia rely fundamentally on the assumption that earthquakes recorded in the past are indicative of where earthquakes will occur in the future. No attempt has yet been made to assess the potential contribution that data from active fault sources might make to the modelling process, despite successful incorporation of such data into United States and New Zealand hazard maps in recent years. In this paper we review the limited history of paleoseismological investigation in Australia and discuss the potential contribution of active fault source data towards improving our understanding of intraplate seismicity. The availability and suitability of Australian active fault source data for incorporation into future probabilistic hazard models is assessed, and appropriate methodologies for achieving this proposed.

Description: Published

Description: JCR Journal

Description: open

Description: Lichenometry is a surface-exposure-dating procedure that complements traditional trench-and-date stratigraphic studies of earthquakes. Lichens on the surficial blocks of a slump in the Seaward Kaikoura Range, South Island, New Zealand provide precise, accurate (± 2 years) dating of 20 post-landslide rockfall events. The coseismic character of these rockfall events is apparent when ages of lichen-size peaks are compared with dates of historical earthquakes. Most local prehistoric lichen-size peaks are synchronous with peaks at other lichenometry sites in a 20 000 km2 region. Lichenometry may be the best paleoseismic tool for describing the extent and intensity of seismic shaking caused by prehistoric earthquakes, and for dating earthquakes generated by concealed thrust faults and subduction fault zones.

Description: Published

Description: JCR Journal

Description: open

Description: New stratigraphic evidence from the Cascadia margin demonstrates that 13 earthquakes ruptured the margin from Vancouver Island to at least the California border following the catastrophic eruption of Mount Mazama. These 13 events have occurred with an average repeat time of ?? 600 years since the first post-Mazama event ?? 7500 years ago. The youngest event ?? 300 years ago probably coincides with widespread evidence of coastal subsidence and tsunami inundation in buried marshes along the Cascadia coast. We can extend the Holocene record to at least 9850 years, during which 18 events correlate along the same region. The pattern of repeat times is consistent with the pattern observed at most (but not all) localities onshore, strengthening the contention that both were produced by plate-wide earthquakes. We also observe that the sequence of Holocene events in Cascadia may contain a repeating pattern, a tantalizing look at what may be the long-term behavior of a major fault system. Over the last ?? 7500 years, the pattern appears to have repeated at least three times, with the most recent A.D. 1700 event being the third of three events following a long interval of 845 years between events T4 and T5. This long interval is one that is also recognized in many of the coastal records, and may serve as an anchor point between the offshore and onshore records. Similar stratigraphic records are found in two piston cores and one box core from Noyo Channel, adjacent to the Northern San Andreas Fault, which show a cyclic record of turbidite beds, with thirty- one turbidite beds above a Holocene/.Pleistocene faunal «datum». Thus far, we have determined ages for 20 events including the uppermost 5 events from these cores. The uppermost event returns a «modern» age, which we interpret is likely the 1906 San Andreas earthquake. The penultimate event returns an intercept age of A.D. 1664 (2 ?? range 1505- 1822). The third event and fourth event are lumped together, as there is no hemipelagic sediment between them. The age of this event is A.D. 1524 (1445-1664), though we are not certain whether this event represents one event or two. The fifth event age is A.D. 1204 (1057-1319), and the sixth event age is A.D. 1049 (981-1188). These results are in relatively good agreement with the onshore work to date, which indicates an age for the penultimate event in the mid-1600 s, the most likely age for the third event of ?? 1500-1600, and a fourth event ?? 1300. We presently do not have the spatial sampling needed to test for synchroneity of events along the Northern San Andreas, and thus cannot determine with confidence that the observed turbidite record is earthquake generated. However, the good agreement in number of events between the onshore and offshore records suggests that, as in Cascadia, turbidite triggers other than earthquakes appear not to have added significantly to the turbidite record along the northernmost San Andreas margin during the last ?? 2000 years.

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Description: JCR Journal

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Description: The Conway Segment of the dextral-slip Hope Fault is one of the fastest slipping fault segments along New Zealand s plate boundary, but has not ruptured co-seismically in the historic period and little paleoseismic data exist to constrain its large earthquake record. Two paleoseismic trenches were opened adjacent to Greenburn Stream near Kaikoura for the 2001 ILP Paleoseismology Conference. Both trenches were excavated into deposits ponded against an uphill-facing shutter scarp. Trench 1, dug through a cobbly soil and surface deposit was dominated by a thick fan/fluvial sequence that was radiocarbon dated at 4409 ± 60 C14 years BP (4844-5288 cal years BP) at the base of the trench. This trench exhibited evidence of complex deformation from many paleoseismic events. The most recent earthquakes are difficult to constrain due to a lack of cover stratigraphy on the fan deposits. However, the modern soil appears to be faulted and is covered by cobbles with a weathering rind-derived age of 220 ± 60 years. Trench 2, dug ?? 50 m to the west has an expanded sequence of the younger cover deposits. Paleoseismic event horizons have been recognised from the combined evidence of upwardterminating faults, offset and mismatched units, a sandblow deposit, and abrupt landscape change shown by the burial of paleosol surfaces that form the event horizons. Two paleosols underlying the modern soil are clearly faulted by two separate rupture events. A dome of sand interpreted as a liquefaction sandblow deposit overlies the lower paleosol (event horizon). Both paleosols are overlain by metre-thick debris deposits, interpreted as earthquake-induced rock avalanches that cascaded off the hillslope following Mw 7 + events. Four radiocarbon dates place some constraints on the timing of the three recent surface-rupturing events. The youngest and lowest date is 548 ± 60 C14 years BP (504-656 cal years BP) and occurs below the lower paleosol. It constrains the maximum duration of time in which the last 2 earthquake events occurred to be 545 years (1295-1840 A.D.). This is consistent with the average Recurrence Interval (RI) of 180-310 years that we determine using two independent paths. The soil record indicates that each event is separated by a significant period of time, comparable to the calculated RI. The most recent event is constrained between ca. 1780 A.D. ± 60 years, taking into account the dates from these trenches, a weathering rind age, and from stratigraphic correlation at the site. Event III probably occurred before 1220 A.D. A maximum dextral slip rate of 23 ± 4 mm/yr is calculated from the minimum fan age and the offset/deflection of a stream channel along the shutter ridge. In concert with the estimate of single event displacement (5-6 m), these results show that the Conway Segment of the Hope Fault is fast-slipping and has ruptured regularly as a result of large earthquakes prior to the European colonisation of New Zealand.

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Description: JCR Journal

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Description: The present study concentrates on the effects on the ionosphere of an individual severe magnetic Storm of the Sudden Commencement (SSC)type,with SSC taking place in the daytime hours.The storm started on 29 October 1968 and went on to 2 November 1968 with geomagnetic 3-hourly magnetic activity index reaching values of Kp 7. Interplanetary magnetic field polarities included A (field polarity Away from the solar wind)positive and T (field polarity Towards the solar wind)negative polarities.In these conditions,the local response of true height of F-region (hF) ionization fails nonlinearly from fixed plasma densities.The interplanetary B z ,the magnetic field H - component and K p were examined for the 5 days following the sudden commencement.Due to intensive geomagnetic SC effects,the lower and upper limits of the F -regions were unbalanced because of gravity relaxation and solar wind pressure effects,until normal levels were restored.In the F -layer 70%deviations of critical frequencies (f 0 F )from median values,as well as hF level variations reaching hundreds of kilometers,were observed and were responsible for the destruction of communication channels.With a plasmapause location value L =1.6 and with K p 7 the protonosphere reservoir should take 1.1 days for its replenishment;one day was in fact insufficient for a full plasma recovery.

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Description: JCR Journal

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Description: A new digital ionosonde called AIS-INGV (Advanced Ionospheric Sounder) was designed both for research and for routine service of HF radio wave propagation forecast. Nearly the entire system was developed in the Laboratorio di Geofisica Ambientale at the Istituto Nazionale di Geofisica e Vulcanologia (INGV), Rome. It exploits advanced techniques for signal analysis, recent technological devices and PC resources. This paper describes design concepts and performance of the new ionosonde.

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Description: JCR Journal

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Description: Paleoseismological analyses were performed along the Campo Imperatore Fault (part of the Gran Sasso Range Fault System) in order to define the seismogenic behaviour (recurrence interval for surface faulting events, elapsed time since the last activation, maximum expected magnitude). Four trenches were excavated across secondary faults which are related to the main fault zone. The youngest event (E1) occurred after 3480-3400 years BP; a previous event (E2) occurred between 7155-7120/7035-6790 years BP and 5590-5565/5545-5475 years BP, while the oldest one (E3) has a Late Pleistocene age. The chronological interval between the last two displacement events ranges between 1995 and 6405 years. The minimum elapsed time since the last activation is 800 years, due to the absence of historical earthquakes which may have been caused by the Campo Imperatore Fault and based on the completeness of the historical catalogues for the large magnitude events in the last eight centuries. Based on the length of the fault surficial expression, earthquakes with M 6.95 may be expected from the activation of the entire Gran Sasso Range Fault System. The effects of the fault activation were investigated through the simulation of a damage scenario obtained by means of the FaCES computer code, made by the National Seismic Survey for civil protection purposes. The damage scenario shows that the activation of the Gran Sasso Range Fault System may be responsible for an earthquake with epicentral intensity I0 10.5 MCS, with a number of collapsed buildings ranging between 7900 and 31100 and a number of damaged buildings ranging between 99 000 and 234 000. The investigated case defines, therefore, a high risk level for the region affected by the Campo Imperatore Fault.

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Description: JCR Journal

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Description: The El Camp Fault (Catalan Coastal Ranges, NE Iberian Peninsula) is a slow slipping normal fault whose seismic potential has only recently been recognised. New geomorphic and trench investigations were carried out during a training course across the El Camp Fault at the La Porquerola alluvial fan site. A new trench (trench 8) was dug close to a trench made previously at this site (trench 4). With the aid of two long topographic profiles across the fault scarp we obtained a vertical slip rate ranging between 0.05 and 0.08 mm/yr. At the trench site, two main faults, which can be correlated between trenches 8 and 4, make up the fault zone. Using trench analysis three paleoseismic events were identified, two between 34.000 and 125.000 years BP (events 3 and 2) and another event younger than 13 500 years BP (event 1), which can be correlated, respectively, with events X (50.000- 125.000 years BP), Y (35.000-50.000 years BP) and Z (3000-25.000 years BP). The last seismic event at the La Porquerola alluvial fan site is described for the first time, but with some uncertainties.

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Description: JCR Journal

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Description: Recent paleoseismic investigations have identified a number of active faults in Northern and Western Thailand. Northern Thailand is an intraplate basin and range province, comprised of north-south-trending Cenozoic intermontane grabens and half grabens, bounded by north- to northwest-striking normal to normal-oblique faults and northeast-striking left-lateral strike-slip faults. The basin-bounding normal faults are marked by steep, linear range fronts with triangular facets and wineglass canyons and have slip rates of 0.1 to 0.8 mm/yr. Based on limited data, the average vertical displacement-per-event is about 1.0 to 1.5 m. These faults are characterized by recurrence intervals of thousands to tens of thousands of years and are capable of generating earthquakes up to moment magnitude (M) 7, and larger. The northeast-striking strike-slip faults are marked by shutter ridges, and deflected drainages. Slip rates are 3 mm/yr or less. Western Thailand is dissected by a number of northwest- and north-northwest-striking, right-lateral strike-slip faults related to the Sagaing Fault in Myanmar. Although showing much less activity than the faults in neighboring Myanmar, these faults display abundant evidence for late Quaternary movement, including shutter ridges, sag ponds, and laterally offset streams. The slip rate on these faults is estimated to be 0.5 to 2.0 mm/yr. These faults are considered capable of generating maximum earthquakes of up to M 71/2.

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Description: JCR Journal

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Description: The Zemuhe Fault is a prominent active fault in Southwestern China. Seven ravines along a 5 km long fault scarp indicate seven large magnitude earthquakes in the Holocene. The youngest four ravines were abandoned during four large magnitude earthquakes, the age of which are constrained by radiocarbon data: ravines 7, 6, and 4 formed in association with the earthquakes at A.D. 1850 and A.D. 814, B.C. 4477 ± 240 or older, and ravine 5 to a paleo-event between B.C. 4477 ± 240 and A.D. 814. Three trenches excavated by earlier workers together with a trench excavated and analyzed here revealed 3 or 4 earthquakes, which are consistent with those indicated by the youngest five ravines. These radiocarbon-dated earthquakes mainly occurred within two temporal clusters: the older cluster of two paleoearthquakes occurred approximately between B.C. 4250 and B.C. 6000, and the younger cluster includes two historical earthquakes of the A.D. 814 and A.D. 1850. Each cluster lasted about 1000-2000 years. A tranquil period of about 5000 years separates the two clusters, during which only one large magnitude earthquake occurred. Moreover, the average recurrence interval of large magnitude earthquake in the Holocene is about 1400-1700 years. Comparison of the maximum horizontal displacement of the A.D. 1850 earthquake, and the 85 ± 5 m cumulative lateral offset over the last 13-15 ka gives the average recurrence interval of 1000-1360 years. The different estimates may arise because moderate and small earthquakes produced a quite high cumulative lateral displacement along the Zemuhe Fault during the Holocene.

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Description: JCR Journal

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Description: The Earth's ionosphere largely determines space weather effects on radio wave communications, navigation and surveillance systems. Lately there has been an increasing demand for ionospheric nowcast and accurate forecast services by various groups of users, including European industry. The paper reviews research activities in Europe based on the exploitation of real-time ground digisondes for the provision of nowcasting and forecasting ionospheric space weather information and useful products and services to support operational applications. During the last few years, important progress in databasing, modelling and forecasting ionospheric disturbances based on real-time data from ground digisondes was achieved in the frames of COST Action 271 «Effects of the Upper Atmosphere on Terrestrial and Earth-Space Communications». Further developments are expected to be deployed with the new COST Action 724 on «Developing the basis for monitoring, modelling and predicting space weather», as well as through the Space Weather Pilot Project of the European Space Agency and through projects funded by the European Commission programmes.

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Description: JCR Journal

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Description: Using the international ground-based network of two-frequency receivers of the GPS navigation system provides a means of carrying out a global, continuous and fully-computerized monitoring of phase fluctuations of signals from satellite-borne radio engineering systems caused by the Earth's inhomogeneous and nonstationary ionosphere. We found that during major geomagnetic storms, the errors of determination of the range, frequency Doppler shift and angles of arrival of transionospheric radio signals exceeds that for magnetically quiet days by one order of magnitude as a minimum. This can be the cause of performance degradation of current satellite radio engineering navigation, communication and radar systems as well as superlong-baseline radio interferometry systems.

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Description: JCR Journal

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Description: Recent seismological studies contribute to better understand the first order characteristics of earthquake occurrence in Italy, identifying the potential sites for moderate to large size earthquakes. Ad hoc passive seismic experiments performed in these areas provide information to focus on the location and geometry of the active faults more closely. This information is relevant for assessing seismic hazard and for accurately constraining possible ground shaking scenarios. The area around the Città di Castello Basin, in the Northern Apennines (Central Italy), is characterized by the absence of instrumental seismicity (M 〉 2.5), it is adjacent to faults ruptured by recent and historical earthquakes. To better understand the tectonics of the area, we installed a dense network of seismic stations equipped with broadband and short period seismometers collecting data continuously for 8 months (October 2000-May 2001). The processing of ~ 900 Gbyte of data revealed a consistent background seismicity consisting of very low magnitude earthquakes (ML 〈 3.2). Preliminary locations of about 2200 local earthquakes show that the area can be divided into two regions with different seismic behaviour: an area to the NW, in between Sansepolcro and Città di Castello, where seismicity is not present. An area toward the SE, in between Città di Castello, Umbertide and Gubbio, where we detected a high microseismicity activity. These findings suggest a probable different mechanical behaviour of the two regions. In the latter area, the seismicity is confined between 0 and 8 km of depth revealing a rather well defined east-dipping, low angle fault 35 km wide that cuts through the entire upper crust down to 12-15 km depth. Beside an apparent structural complexity, fault plane solutions of background seismicity reveal a homogeneous pattern of deformation with a clear NE-SW extension.

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Description: JCR Journal

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Description: A wideband HF simulator has been constructed that is based on a detailed physical model. It can generate an output giving a time realization of the HF wideband channel for any HF carrier frequency and bandwidth and for any given transmitter receiver path, time of day, month and year and for any solar activity/geomagnetic conditions. To accomplish this, a comprehensive solution has been obtained to the problem of HF wave propagation for the most general case of a 3D inhomogeneous ionosphere with time-varying electron density fluctuations. The solution is based on the complex phase method (Rytov s method), which has been extended to the case of an inhomogeneous medium and a point source of the field. Results of simulation obtained according to the technique developed have been presented, calculated for a single-hop path 1000 km long oriented to the south from St. Petersburg and including a horizontal electron density gradient present in the IRI model used as the basis of the ionosphere model. The fluctuations of the ionospheric electron density were characterized by an inverse power law anisotropic spatial spectrum. For this model, the random walk of the phasor at the receiver is determined and shown both for paths reflected in the E- and Fregions, being significantly larger for the latter. The oblique sounding ionogram is constructed and reveals three propagation modes: the E-mode and low and high angle F-mode paths. The time-varying field due to each of these paths is then summed at the receiving location enabling the calculation of the scattering function and also the time realization of the received signal shown as a function of both fast and slow time. This is performed both with and without the presence of the geomagnetic field; in the former case the splitting of the F2-mode into both e- and o-modes is seen. It is also shown how the scattering function can be obtained from the time realization of the channel in a way akin to experimental determination of the scattering function from channel measurements. Results from the simulations show the very significant effect of irregularities of even modest magnitude and the comparative effects due to background ionosphere dispersion and the fluctuating irregularities as well as geomagnetic mode splitting. Since the simulator is based on a physical model, it should be possible by comparison of experimental results and simulation to identify the correspondence between physical parameters (e.g., the variance and anisotropy of the electron density fluctuations, orientation of the propagation path to the magnetic meridian, bulk ionosphere motions) with observed channel parameters (e.g., Doppler spread and shift, time delay spread).

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Description: JCR Journal

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Description: Electron content statistics offers important information for planning and operation of various application systems that make use of the transionospheric propagation of radio signals. Electron content statistics meet with an important difficulty: the majority of data stem from observations on the radio signals of orbiting satellites. The database for vertical electron content derived from observations of radio signals emitted from geostationary satellites is only very small. Therefore it is important to make use of statistics for peak density from ionosonde measurements. Quantile statistics do not contain information about ionization extremes. Therefore it is necessary to complement the statistics with case studies which reveal unusual and extreme electron content structures in space and in time.

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Description: JCR Journal

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Description: The Total Electron Content (TEC) of the ionosphere is a key parameter for describing the ionospheric state. This paper deals with the large scale behaviour of TEC under low and high solar activity conditions. Large scale structures of the plasma density are formed by fundamental ionospheric processes mainly driven by solar radiation input, neutral winds and electric fields. The monitoring of large scale structures contributes to a comprehensive understanding of these coupling mechanisms which are rather complex particularly under perturbed geomagnetic conditions. The paper addresses techniques to monitor TEC with sufficient accuracy of a few TEC units (1016m-2) to measure large scale structures over Europe and over the polar areas. The availability of GPS data from global GPS receiver networks as e.g., those from the International GPS Service (IGS) is dense enough to generate TEC maps on a continuous base. A model assisted technique is briefly described for mapping TEC over the European and polar areas. A statistical estimation of horizontal TEC gradients reveals large scale gradients of up to about 6 TECU/1000 km under high solar activity conditions at an occurrence probability level of about 1%. Occasionally, during severe ionospheric storms this value may increase by a factor of 10 or even more. A close correlation of large scale gradients and the geomagnetic activity has been found giving the chance to forecast TEC gradient amplitudes by using predicted geomagnetic indices. Since TEC is proportional to first-order range errors in Global Satellite Navigation Systems (GNSS) such as the US GPS and the Russian GLONASS the study of the behaviour of this parameter has a practical meaning in GNSS based navigation and positioning. The paper addresses the close relationship between TEC and ranging errors in GNSS. Having in view Galileo, the planned Europes own global satellite navigation system, some aspects related to the mitigation of ionospheric propagation errors within the European Geostationary Navigation Overlay System (EGNOS) are discussed. Since EGNOS will augment the two above mentioned satellite navigation systems and make them suitable for safety critical applications such as flying aircraft or navigating ships through narrow channels the ionospheric propagation errors have to be mitigated as much as possible.

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Description: JCR Journal

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Description: The aim of this paper is to present a high data rate transmission system through the ionospheric channel in the HF-band (3-30 MHz). The applications expected in this study are image transmitting and real-time videoconferencing. Very high rates are required compared to the standard modems. Therefore, an array processing is performed with a set of antennas whose spatial response differs from one another arranged in a circular array or in a collocated sensor. Synchronization (Zero Crossing Detector) and source separation (LMS algorithm) resort to classical well-tested techniques involving training sequences. Experimental results are presented for both antenna configurations. These techniques improve data rate, reaching 20 kbits/s within the 6 kHz bandwidth (QAM 64) without coding or interleaving.

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Description: JCR Journal

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Description: The «prediction» and «forecast» of the critical frequency of the F 2 layer (f0 F2 ) is an important issue for frequency planning in short wave radio communications. In this context, «prediction» is used for the determination of monthly median values of f0 F2 for each hour, while «forecast» denotes the determination of hourly values. In a previous paper we proposed a «sliding window» technique for prediction combined with «feedback» for forecast (Bilge and Tulunay, 2000). In the present paper we obtain the variation of the feedback coefficient with R 12 and geographic latitude.

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Description: JCR Journal

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Description: The paper reviews the work done in the course of the COST 271 Action concerned with the development of tools and methods for forecasting, nowcasting and warning of ionospheric propagation conditions. Three broad categories of work are covered. First, the maintenance and enhancement of existing operational services that provide forecast or nowcast data products to end users; brief descriptions of RWC Warsaw and the STIF service are given. Second, the development of prototype or experimental services; descriptions are given of a multi-datasource system for reconstruction of electron density profiles, and a new technique using real-time IMF data to forecast ionospheric storms. The third category is the most wide-ranging, and deals with work that has presented new or improved tools or methods that future operational forecasting or nowcasting system will rely on. This work covers two areas - methods for updating models with prompt data, and improvements in modelling or our understanding of various ionospheric-magnetospheric features - and ranges over updating models of ionospheric characteristics and electron density, modelling geomagnetic storms, describing the spatial evolution of the mid-latitude trough, and validating a recently-proposed technique for deriving TEC from ionosonde observations.

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Description: JCR Journal

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Description: The evaluation of any earthquake forecast hypothesis requires the application of rigorous statistical methods. It implies a univocal definition of the model characterising the concerned anomaly or precursor, so as it can be objectively recognised in any circumstance and by any observer.A valid forecast hypothesis is expected to maximise successes and minimise false alarms. The probability gain associated to a precursor is also a popular way to estimate the quality of the predictions based on such precursor. Some scientists make use of a statistical approach based on the computation of the likelihood of an observed realisation of seismic events, and on the comparison of the likelihood obtained under different hypotheses. This method can be extended to algorithms that allow the computation of the density distribution of the conditional probability of earthquake occurrence in space, time and magnitude. Whatever method is chosen for building up a new hypothesis, the final assessment of its validity should be carried out by a test on a new and independent set of observations. The implementation of this test could, however, be problematic for seismicity characterised by long-term recurrence intervals. Even using the historical record, that may span time windows extremely variable between a few centuries to a few millennia, we have a low probability to catch more than one or two events on the same fault. Extending the record of earthquakes of the past back in time up to several millennia, paleoseismology represents a great opportunity to study how earthquakes recur through time and thus provide innovative contributions to time-dependent seismic hazard assessment. Sets of paleoseimologically dated earthquakes have been established for some faults in the Mediterranean area: the Irpinia fault in Southern Italy, the Fucino fault in Central Italy, the El Asnam fault in Algeria and the Skinos fault in Central Greece. By using the age of the paleoearthquakes with their associated uncertainty we have computed, through a Montecarlo procedure, the probability that the observed inter-event times come from a uniform random distribution (null hypothesis). This probability is estimated approximately equal to 8.4% for the Irpinia fault, 0.5% for the Fucino fault, 49% for the El Asnam fault and 42% for the Skinos fault. So, the null Poisson hypothesis can be rejected with a confidence level of 99.5% for the Fucino fault, but it can be rejected only with a confidence level between 90% and 95% for the Irpinia fault, while it cannot be rejected for the other two cases. As discussed in the last section of this paper, whatever the scientific value of any prediction hypothesis, it should be considered effective only after evaluation of the balance between the costs and benefits introduced by its practical implementation.

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Description: JCR Journal

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Description: The existing uncertainties about the electron density profiles in the topside ionosphere, i.e., in the height region from h m F 2 to ~ 2000 km, require the search for new data sources. The ISIS and Alouette topside sounder satellites from the sixties to the eighties recorded millions of ionograms but most were not analyzed in terms of electron density profiles. In recent years an effort started to digitize the analog recordings to prepare the ionograms for computerized analysis. As of November 2001 about 350 000 ionograms have been digitized from the original 7-track analog tapes. These data are available in binary and CDF format from the anonymous ftp site of the National Space Science Data Center. A search site and browse capabilities on CDAWeb assist the scientific usage of these data. All information and access links can be found at http://nssdc.gsfc.nasa.gov/space/isis/isis-status. html. This paper describes the ISIS data restoration effort and shows how the digital ionograms are automatically processed into electron density profiles from satellite orbit altitude (1400 km for ISIS-2) down to the F peak. Because of the large volume of data an automated processing algorithm is imperative. The TOPside Ionogram Scaler with True height algorithm TOPIST software developed for this task is successfully scaling ~ 70% of the ionograms. An «editing process» is available to manually scale the more difficult ionograms. The automated processing of the digitized ISIS ionograms is now underway, producing a much-needed database of topside electron density profiles for ionospheric modeling covering more than one solar cycle.

Description: Published

Description: JCR Journal

Description: open