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: Nella Struttura Terremoti dell’INGV la Linea di Attività T5 “Sorveglianza sismica ed operatività postterremoto” si occupa delle attività di sviluppo di strumenti e procedure per la valutazione in tempo reale degli effetti di terremoti e tsunami e della gestione delle emergenze sismiche. Uno dei suoi obiettivi del 2015 era la formalizzazione dei protocolli di intervento di Gruppi d’Emergenza, avvenuta per Emergeo, Emersito, IES, QUEST e Sismiko con Decreto del Presidente nel luglio 2015. Altro obiettivo era l’elaborazione di un Protocollo di Ente per la gestione delle emergenze sismiche. La bozza preparata nel 2015 prevede l’importante novità dell’Unità di Crisi, mai formalizzata in precedenza. Attraverso questo Protocollo di Ente si auspica di migliorare la risposta logistico-operativa dell’INGV durante l’emergenza, di avere una più rapida conoscenza del fenomeno in corso e di realizzare un’efficace comunicazione verso Protezione Civile, media e pubblico. Per verificare il tutto è stata organizzata un’esercitazione in cui è stato simulato un terremoto di magnitudo 6.4 nel basso Lazio. Si sono così sperimentate l’efficacia del flusso azioni/informazioni durante un’emergenza, il funzionamento dell’Unità di Crisi, la funzionalità dei protocolli dei Gruppi d’Emergenza, l’efficienza delle attività in sede per gli aspetti tecnico-logistici, il flusso di comunicazione interno e le comunicazioni istituzionali esterne (queste ultime simulate). In questo articolo sono descritte le fasi di organizzazione ed attuazione dell’esercitazione. Inoltre, durante il suo svolgimento, la valutazione dell’efficacia dell’organizzazione e delle attività svolte dai gruppi coinvolti è stata affidata ad alcuni osservatori e qui è allegata l’elaborazione dei commenti riportati. Abbiamo fatto infine una sintesi dei risultati positivi e delle criticità emerse dall’esercitazione, attività così importante a nostro avviso da considerarne indispensabile la ripetizione con cadenza quanto meno annuale.

Description: Published

Description: 1SR. TERREMOTI - Servizi e ricerca per la Società

Description: N/A or not JCR

Description: open

Description: In the summer of 1995 a teleseismic transect was deployed across the central Apennines. It is the second of a series of passive seismic field experiments (Figure 1) planned for inferring information on the crust and the upper mantle beneath the Italian region. These studies on the deep structure are part of a m u l t i d i s c i p l i n a ry two years project "Geodynamic Modeling of an active Region of the Mediterranean: The Apennines" funded by the European Community (contract EV5V-0464), whose final goal is the definition of a g e o d y n a m i c model of the Apennines based on a variety of geological and geophysical studies. For more details on the project see the Report on the Northern Apennines teleseismic transect (Amato et al., 1995).

Description: Published

Description: 1IT. Reti di monitoraggio e Osservazioni

Description: N/A or not JCR

Description: open

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: 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 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: (extended abstract)

Description: INGV, Regione Sicilia, Ministero Sviluppo Economico

Description: Published

Description: Ettore Majorana Foundation and Centre for Scientific Culture, Erice, Sicily

Description: 3.2. Tettonica attiva

Description: 3.3. Geodinamica e struttura dell'interno della Terra

Description: 5.9. Formazione e informazione

Description: open

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: A station (FAGN) installed on a segment of the fault system that generated the April 2009 L’Aquila earthquakes shows larger ground motions compared to nearby stations. Spectral ratios using 304 earthquakes result in a station amplification significantly varying event by event in the frequency band 1–8 Hz. The resulting pattern of amplitude dependence on causative earthquake location reveals that the strongest (up to a factor of 10) amplifications occur for tightly clustered aftershocks aligned with the fault dip beneath FAGN thus indicating a fault‐guided effect. Fault models are investigated in a grid‐search approach by varying velocity, Q, width and depth of the fault zone. Although the problem solution is not unique and there are strong trade‐offs among the model parameters, constraints from observations yield a deep trapping structure model where the most likely values of velocity reduction, Q and damage zone width are 25%, 20, and 280 m, respectively.

Description: Published

Description: L24305

Description: 3.1. Fisica dei terremoti

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: JCR Journal

Description: reserved

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: We present rupture details of the Mw 6.3 April 6, 2009 L’Aquila earthquake derived by back‐projecting teleseismic P waves. This technique has previously been applied to large magnitude earthquakes, but this is the first application to a moderate size event. We processed vertical‐component seismograms for 60 broadband stations obtained from the Incorporated Research Institutions for Seismology (IRIS) data center. The traces were aligned and normalized using a multi‐channel cross‐correlation algorithm and 4th root stacking was used to image the rupture. We found that the L’Aquila earthquake ruptured towards the south and that a second discrete pulse of energy occurred 20–25 km east of the epicenter about 17–18 s after the nominal origin time. The spatial extent of the rupture image correlates well with a post‐seismic survey of damage in the region. Because the technique is potentially very fast (images can be produced within 20–30 minutes of the origin time), it may be useful to governmental agencies tasked with emergency response and rescue.

Description: Published

Description: L03301

Description: 4.2. TTC - Modelli per la stima della pericolosità sismica a scala nazionale

Description: JCR Journal

Description: reserved

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: On April 6 2009, a Mw=6.3 earthquake occurred in the central Apennines (Italy) damaging L’Aquila city and the surrounding country. We relocate the October 2008-April 6 2009 foreshocks and about 2000 aftershocks occurred between April 6 and April 30 2009, by applying a double-difference technique and determine the stress field from focal mechanisms. The events concentrate in the upper 15 km of the crust. Three main NW-SE to NNW-SSE striking, 30°-45° and 80°-90° dipping faults activate during the seismic sequence. Among these, a normal fault and a thrust were re-activated with dip-slip movements in response to NE-SW extension. The structural maturity of the seismogenic fault system is lower than that displayed by other systems in southern Apennines, because of the lower strain rate of the central sector of the chain with respect to the southern one. VP/VS increases progressively from October 2008 to the April 6 2009 mainshock occurrence along a NW-SE strike due to an increment in pore fluid pressure along the fault planes. Pore pressure diffusion controls the space-time evolution of aftershocks. A hydraulic diffusivity of 80 m2/s and a seismogenic permeability of about 10-12 m2 suggest the involvement of gas-rich (CO2) fluids within a highly fractured medium. Suprahydrostatic, high fluid pressure (about 200 MPa at 10 km of depth) within overpressurized traps, bounded by pre-existing structural and/or lithological discontinuities at the lower-upper crust boundary, are required to activate the April 2009 sequence. Traps are the storage zone of CO2-rich fluids uprising from the underlying, about 20 km deep, metasomatized mantle wedge. These traps easily occur in extensional regimes like in the axial sector of Apennines, but are difficult to form in strike-slip regimes, where sub-vertical faults may cross the entire crust. In the Apennines, fluids may activate faults responsible for earthquakes up to Mw=5-6. Deep fluids more than tectonic stress may control the seismotectogenesis of accretionary wedges.

Description: Published

Description: B06315

Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale

Description: 3.1. Fisica dei terremoti

Description: JCR Journal

Description: open

Description: Effective tsunami early warning for coastlines near a tsunamigenic earthquake requires notification within 5-15 minutes. We have shown recently that tsunamigenic earthquakes have an apparent rupture duration, T0, greater than about 50 s. Here we show that T0 gives more information on tsunami importance than moment magnitude, Mw, and we introduce a procedure using seismograms recorded near an earthquake to rapidly determine if T0 is likely to exceed T=50 or 100 s. We show that this “duration-exceedance” procedure can be completed within 3-10 min after the earthquake occurs, depending on station density, and that it correctly identifies most recent earthquakes which produced large or devastating tsunamis. This identification forms a complement to initial estimates of the location, depth and magnitude of an earthquake to improve the reliability of tsunami early warning, and, in some cases, may make possible such warning.

Description: DPC-S3 2007-2009

Description: Published

Description: L09306

Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale

Description: JCR Journal

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: Seismic recordings are immediately available when an earthquake occurs. Their analysis allows the reconstruction of the rupture dynamics by means of sophisticated techniques, which usually need some tests to provide robust results. However, immediate information on the source kinematics is required in order to imagine the fault location and extent and quickly reconstruct the areas of stress release and subsequent accumulation. Very simple analysis may provide useful information, giving insight in source complexity. Right after the 6 April 2009 L'Aquila earthquake (MW = 6.3), we analyzed the seismograms recorded at broadband and strong motion stations and provided firm constraints on rupture kinematics, slip distribution, and static surface deformation, also discriminating the actual fault plane. The fracture occurred in two stages, with initial updip propagation, successively proceeding toward SE, possibly on a different plane. We also analyzed the strongest aftershock (MW = 5.6), showing that useful indications could be retrieved for lower magnitude events.

Description: Published

Description: L23305

Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale

Description: JCR Journal

Description: 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: In questo lavoro vengono presentati e discussi i risultati del rilievo macrosismico effettuato in termini di European Macroseismic Scale 1998 del terremoto del 15 dicembre 2009. L’evento, di Ml 4.2, ha colpito la Valle del Tevere tra le province di Terni e Perugia, ed ha avuto una intensità EMS pari al 7 grado. Il rilievo è servito anche come test sull’uso della scala EMS98, non ancora utilizzata sistematicamente per i terremoti italiani, attraverso un’indagine di dettaglio nelle quattro località più danneggiate. Il tentativo di una applicazione rigorosa della scala ha fatto emergere alcune problematiche metodologiche, di fronte alle quali sono state fatte delle scelte in linea con le Linee Guida della scala. In particolare l’adozione del grado intero ci sembra l’alternativa più robusta per contrastare la abusata tentazione di usare la scala macrosismica come una misura continua dello scuotimento. This paper shows the results of the macroseismic survey of the December 15, 2009 earthquake, performed according to the EuropeanMacroseismic Scale 1998. The event (Ml 4.2), hit the Tiber Valley, between the Terni and Perugia provinces has been evaluated of intensity 7. As the EMS98 is not yet systematically used for Italian earthquakes, we tested it by means of a detailed survey in the most damaged localities. The several methodological questions arisen led us to make some choices according to the Guidelines of the EMS98, in the intensity assessment. Particularly effective is, in our opinion, the choice to preserve the integer character of the scale, and not use intermediate formulations of the intensity degree. 4

Description: Published

Description: 1-21

Description: 1.11. TTC - Osservazioni e monitoraggio macrosismico del territorio nazionale

Description: N/A or not JCR

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: The evolution of the frictional strength along a fault at seismic slip rates (about 1 m/s) is a key factor controlling earthquake mechanics. At mantle depths, friction-induced melting and melt lubrication may influence earthquake slip and seismological data. We report on laboratory experiments designed to investigate dynamic fault strength and frictional melting processes in mantle rocks. We performed 20 experiments with Balmuccia peridotite in a high-velocity rotary shear apparatus and cylindrical samples (21.8 mm in diameter) over a wide range of normal stresses (5.4–16.1 MPa), slip rates (0.23–1.14 m/s), and displacements (1.5–71 m). During the experiments, shear stress evolved with cumulative displacement in five main stages (stages 1–5). In stage 1 (first strengthening), the coefficient of friction m increased up to 0.4–0.7 (first peak in friction). In stage 2 (abrupt firstweakening), m decreased to about 0.25–0.40. In stage 3 (gradual second strengthening), shear stress increased toward a second peak in friction (m = 0.30–0.40). In stage 4 (gradual second weakening), the shear stress decreased toward a steady state value (stage 5) with m = 0.15. Stages 1 and 2 are of too short duration to be investigated in detail with the current experimental configuration. By interrupting the experiments during stages 3, 4, and 5, microstructural (Field Emission Scanning Electron Microscope) and geochemical (Electron Probe Micro-Analyzer and Energy Dispersive X-Ray Spectroscopy) analysis of the slipping zone suggest that second strengthening (stage 3) is associated with the production of a grain-supported melt-poor layer, while second weakening (stage 4) and steady state (stage 5) are associated with the formation of a continuous melt-rich layer with an estimated temperature up to 1780 C. Microstructures formed during the experiments were very similar to those found in natural ultramafic pseudotachylytes. By performing experiments at different normal stresses and slip rates, (1) the ‘‘thermal’’ (as it includes the thermally activated first and second weakening) slip distance to achieve steady state from the first peak in strength decreased with increasing normal stress and slip rate and (2) the steady state shear stress slightly increased with increasing normal stress and, for a given normal stress, decreased with increasing slip rate. The ratio of shear stress versus normal stress was about 0.15, well below the typical friction coefficient of rocks (0.6–0.8). The dependence of steady state shear stress with normal stress was described by means of a constitutive equation for melt lubrication. The presence of microstructures similar to those found in natural pseudotachylytes and the determination of a constitutive equation that describes the experimental data allows extrapolation of the experimental observations to natural conditions and to the study of rupture dynamics in mantle rocks.

Description: FIRB-MIUR project ‘‘Sviluppo Nuove Tecnologie per la Protezione e Difesa del Territorio dai Rischi Naturali. Progetti di Eccellenza Fondazione Cassa di Risparmio di Padova e Rovigo (CARIPARO) The European Research Council Starting Grant Project 205175 (USEMS)

Description: Published

Description: B06306

Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce

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: 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: The Non-Critical Precursory Accelerating Seismicity Theory (PAST) has been proposed recently to explain the formation of accelerating seismicity (increase of the a-value) observed before large earthquakes. In particular, it predicts that precursory accelerating seismicity should occur in the same spatiotemporal window as quiescence. In this first combined study we start by determining the spatiotemporal extent of quiescence observed prior to the 1997Mw= 6Umbria-Marche earthquake, Italy, using the RTL (Region-Time-Length) algorithm. We then show that background events located in that spatiotemporal window form a clear acceleration, as expected by the Non-Critical PAST. This result is a step forward in the understanding of precursory seismicity by relating two of the principal patterns that can precede large earthquakes.

Description: Published

Description: L15306

Description: 3.1. Fisica dei terremoti

Description: JCR Journal

Description: reserved

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: On 29 June 1170 a large earthquake hit a vast area in the Near Eastern Mediterranean, comprising the present-day territories of western Syria, central southern Turkey, and Lebanon. Although this was one of the strongest seismic events ever to hit Syria, so far no in-depth or specific studies have been available. Furthermore, the seismological literature (from 1979 until 2000) only elaborated a partial summary of it, mainly based solely on Arabic sources. The major effects area was very partial, making the derived seismic parameters unreliable. This earthquake is in actual fact one of the most highly documented events of the medieval Mediterranean. This is due to both the particular historical period in which it had occurred (between the second and the third Crusades) and the presence of the Latin states in the territory of Syria. Some 50 historical sources, written in eight different languages, have been analyzed: Latin (major contributions), Arabic, Syriac, Armenian, Greek, Hebrew, Vulgar French, and Italian. A critical analysis of this extraordinary body of historical information has allowed us to obtain data on the effects of the earthquake at 29 locations, 16 of which were unknown in the previous scientific literature. As regards the seismic dynamics, this study has set itself the question of whether there was just one or more than one strong earthquake. In the former case, the parameters (Me 7.7 ± 0.22, epicenter, and fault length 126.2 km) were calculated. Some hypotheses are outlined concerning the seismogenic zones involved.

Description: Published

Description: B07304

Description: 3.10. Sismologia storica e archeosismologia

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: On 10 September 2005 at 1711 LT (1511 UT) a loud boom was heard on the Ischia island. A clear seismic signal was also recorded by the seismic monitoring network of the Neapolitan volcanic areas (Ischia, Campi Flegrei, and Mount Vesuvius) and on a regional station (Mount Massico). On the basis of the seismic recordings and on acoustic phenomena reports, we relate this event to the atmospheric explosion (airburst) of a bolide about 15 km SW of Ischia at an elevation of about 11.5 km. The location has been obtained through nonlinear traveltime inversion in a realistic atmospheric model including wind effects. We show, using statistical estimators, how the traveltime pattern is due to both atmospheric winds and the bolide trajectory. Using the same reasoning we discard a human origin (supersonic jet or sea-air missile). In addition, we also propose a new algorithm for fast acoustic traveltime computation for a supersonic moving source.

Description: Published

Description: B10307

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: 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: To comply with nuclear safety requirements, an in-depth research program for the revision of existing catalogues was initiated back in 1974. The priority of the partners involved in the SISFRANCE project was to establish the most exhaustive documentary databank in order to construct an intensity macroseismic database, concerning both epicentral and punctual observations. The architecture of the SISFRANCE database is presented. The strength of this parametric database is the attribution of reliability coefficients at all levels of interpretations going from the documentary sources to the final intensity estimate. To ensure homogeneity of the database, a general guideline was defined. The resulting macroseismic relational database SISFRANCE contains 65000 intensity observations attesting to the existence of 5283 earthquakes (575 with Io = VI) that have been felt on the French metropolitan territory over the past one thousand years. Thanks to the homogeneous methodology and to the continuous collaboration between BRGM, EDF and IRSN for the past 30 years, SISFRANCE is today a reference database and a key tool for seismic hazard assessment.

Description: Published

Description: JCR Journal

Description: open

Description: The central and eastern United States has experienced only 5 historic earthquakes with Mw 7.0, four during the New Madrid sequence of 1811-1812: three principal mainshocks and the so-called «dawn aftershock» following the first mainshock. Much of the historic earthquake research done in the United States has focused on the New Madrid Seismic Zone (NMSZ), because the largest New Madrid earthquakes may represent the archetype for the most damaging earthquakes to be expected in intraplate regions. Published magnitude values ranging from 7.0 to 8.75 have generally been based on macroseismic effects, which provide the most direct constraint on source size for the events. Critical to the interpretation of these accounts is an understanding of their historic context. Early settlments clustered along waterways, where substantial amplification of seismic waves is expected. Analyzing the New Madrid intensity values with a consideration of these effects yields preferred values of Mw 7.2-7.3, 7.0, and 7.4-7.5 for the December, January, and February mainshocks, respectively, and of 7.0 for the «dawn aftershock». These values are consistent with other lines of evidence, including scaling relationships. Finally, I show that accounts from the New Madrid sequence reveal evidence for remotely triggered earthquakes well outside the NMSZ. Remotely triggered earthquakes represent a potentially important new wrinkle in historic earthquake research, as their ground motions can sometimes be confused with mainshock ground motions.

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: This work presents a summary on the development of studies of historical earthquakes in Armenia and adjacent parts of Turkey and Iran. Since ancient times, this region has been an arena where active geodynamic and seismic history intermingled with no less active and dynamic evolution of human cultures and societies. A long-term historical record in this region beginning as early as the 8th century B.C. provides abundant evidence that can make an inestimable contribution to studies of historical seismicity and volcanism in the area. We discuss the main research methodology and sources used, and dwell on the principal catalogues of historical earthquakes compiled to date.

Description: Published

Description: JCR Journal

Description: open

Description: The use of modern broadband seismometers allows the observation of dynamic and static near-field effects. In the fortunate case of the great 1994 Bolivia earthquake a 6 mm coseismic permanent offset was observed at distances of about 600 km. On the other hand no surface static displacement from moderate events has been observed yet. This is mainly due to the intrinsic difficulties in the instrument removal. In the present paper we analyze broadband waveforms from a couple of events in southern Italy, recorded at distance of 50 km, by applying the technique for instrument removal recently introduced by Zhu [2003]. We derive stable and reliable measures of very small coseismic static offset produced by moderate magnitude earthquakes. Our results, successfully tested against synthetic prediction, give permanent displacement of a few tenths of millimeters, one order of magnitude smaller than usual geodetic resolution.

Description: Published

Description: N/A or not JCR

Description: reserved

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: A geodynamic interpretation of the Northern Marche region is diffi cult, the zone being characterized by complex structures which cannot be defi ned in the form of a simple, standard model. It is unquestionable that the geodynamic setting, whatever it is, bears a strong infl uence on the seismic hazard assessment of a region, and this is the background reason for the present note. In order to obtain a more detailed picture of seismological evidence in this zone, 11 new fault plane solutions of crustal events with 2.9 〈 M 〈 4.3 were calculated, using data recorded by the national seismic network of the Istituto Nazionale di Geofi sica e Vulcanologia in the period 1990-2000. The aim is to add local information to the previous studies by Frepoli and Amato (1997, 2000). A possible result of this new study is the division of the Northern Marche region into three areas with different focal mechanism categories: the inner area of the Apenninic belt, the Adriatic on-shore and the Adriatic off-shore. This note is intended to be a contribution to update seismological evidence in the Northern Marche region.

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: 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: 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: 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: 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: 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: 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: A damaging earthquake of Mw 7.7, which struck the Bhuj region of India on January 26, 2001, was followed by a large number of aftershocks. The aftershock data available at Gauribidanur Seismic Array Station (GBA), India, till 869 h following the main shock were compiled. The plot of the aftershocks rate with time was found to be oscillatory decay. There was a sharp decrease of the aftershocks rate in the initial 144 h from the main shock and this paper presents the analysis of the temporal characteristics of aftershock activity during this period. Astatistical best fit for the rate of aftershocks is performed using the generalised Omoris law and the exponential decay law. The statistical errors for the exponential fit are found to be lower than that of the generalised Omori's fit. The superimposed oscillations present in the aftershock activity are extracted by differencing the observed aftershock activity from the statistical fits. The frequencies of these oscillations are found to be 0.062 h1, 0.078 h-1, 0.102 h-1, 0.118 h-1, 0.141 h-1, 0.164 h-1, 0.233 h-1 and 0.476 h-1. Some of the plausible causes for this kind of oscillations present in the aftershock activity are also discussed in this paper.

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Description: We determined a set of empirical functions that describe the spectral amplitude decay of S-waves with distance in Southern Italy. We analyzed 32 earthquakes with magnitudes ML 2.0-5.4 and hypocentral distances ranging between 12 and 216 km. We obtained attenuation functions for 14 frequencies(1.0〈 f〈20.0 Hz). We compared these functions with average non-parametric attenuation functions reported by Castro et al. (1999) for different regions of Italy, and we observe that at low frequencies (f〈5.0 Hz) the spectral amplitudes from earthquakes in Southern Italy decay faster than the average. However, at high frequencies ( f 〉 5.0 Hz), the spectral amplitudes are above the average. At higher frequencies ( f 〉 10 Hz), the attenuation functions obtained for Southern Italy are slightly above the standard deviation of the average attenuation functions. It is possible that in this frequency range (10-20 Hz) site effects may influence the amplitude decay. In order to quantify the attenuation of the S-waves, we estimated the quality factor Q modeling the empirical attenuation functions using the following parametric form: A( f , r)=10/r b·e- pfR/Q ß; where 1.6 = f = 10.0 Hz is the frequency band with minimum effect of instrument and site response, r = 120 km is the distance range where the rate of decay of the spectral amplitudes is approximately constant, R=(r-10) and ß=3.2 km/s. We found that the exponent b=1.0±0.2 in the frequency band analyzed and Q shows a frequency dependence that can be approximated by the function Q=32.1 f 1.7.

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Description: Historical studies of earthquakes in Australia using information dating back to 1788 have been comprehensive, if not exhaustive. Newspapers have been the main source of historical earthquake studies. A brief review is given here with an introduction to the pre-European aboriginal dreamtime information. Some of the anecdotal information of the last two centuries has been compiled as isoseismal maps. Relationships between isoseismal radii and magnitude have been established using post-instrumental data allowing magnitudes to be assigned to the pre-instrumental data, which can then be incorporated into the national earthquake database. The studies have contributed to hazard analyses for the building codes and stimulated research into microzonation and paleo-seismology.

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Description: The assessment of the completeness of historical earthquake data (such as, for instance, parametric earthquake catalogues) has usually been approached in seismology - and mainly in Probabilistic Seismic Hazard Assessment(PSHA) - by means of statistical procedures. Such procedures look «inside» the data set under investigation and compare it to seismicity models, which often require more or less explicitly that seismicity is stationary. They usually end up determining times (Ti), from which on the data set is considered as complete above a given magnitude (Mi); the part of the data set before Ti is considered as incomplete and, for that reason, not suitable for statistical analysis. As a consequence, significant portions of historical data sets are not used for PSHA. Dealing with historical data sets - which are incomplete by nature, although this does not mean that they are of low value - it seems more appropriate to estimate «how much incomplete» the data sets can be and to use them together with such estimates. In other words, it seems more appropriate to assess the completeness looking «outside » the data sets; that is, investigating the way historical records have been produced, preserved and retrieved. This paper presents the results of investigation carried out in Italy, according to historical methods. First, the completeness of eighteen site seismic histories has been investigated; then, from those results, the completeness of areal portions of the catalogue has been assessed and compared with similar results obtained by statistical methods. Finally, the impact of these results on PSHA is described.

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Description: China is one of the countries with the longest tradition of culture and has suffered many earthquake disasters, so many earthquake documents have therefore been conserved. In this paper we try to outline some basic information of historical earthquake investigation and research in China, such as collection of historical earthquake data from archives, historical earthquake catalogues, seismic intensity scales. We introduce briefly the huge accomplishments of historical research and discuss some problems encountered. Through examples, we illustrate the solutions to some typical problems. There are some suggestions on further work.

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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: In Colombia are available a discreet number of historical seismology investigations, dating back 50 years. This paper reviews basic information about earthquakes studies in Colombia, such as primary sources, compilation of descriptive catalogues and parametric catalogues. Father Jesús Emilio Ramírez made the main systematic study before 1975. During the last 20 years, great earthquakes hit Colombia and, as consequence, historical seismology investigation was developed in the frame of seismic hazard projects.

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Description: The 1985 Mexican earthquakes demonstrated that knowledge concerning their history was still scarce and precarious.In fact those earthquakes acted as triggers, because it was then when a new field of research began to develop: disaster historical research. An initial task was to retrieve the history of earthquakes in Mexico in order throughout to produce an exhaustive inventory. The main result was a paradigmatic catalogue, published some years ago as the book Los sismos en la historia de México (Earthquakes in Mexican History). It contains information about every event along 450 years of Mexican seismological history. This paper will focus on the background of this seismological compilation and its characteristics, addressing mainly methodological items concerning sources, qualitative and/or quantitative data, the importance of joint and multidisciplinary efforts, and the research they have inspired on historical earthquakes investigation in Mexico.

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Description: The Dead Sea Fault and its junction with the southern segment of the East Anatolian fault zone, despite their high tectonic activity have been relatively quiescent in the last two centuries. Historical evidence, however, shows that in the 12th century these faults ruptured producing the large earthquakes of 1114, 1138, 1157 and 1170. This paroxysm occurred during one of the best-documented periods for which we have both Occidental and Arab chronicles, and shows that the activity of the 20th century, which is low, is definitely not a reliable guide to the activity over a longer period. The article is written for this Workshop Proceedings with the archaeoseismologist, and in particular with the seismophile historian in mind. It aims primarily at putting on record what is known about the seismicity of the region in the 12th century, describe the problems associated with the interpretation of macroseismic data, their limitations and misuse, and assess their completeness, rather than answer in detail questions regarding the tectonics and seismic hazard of the region, which will be dealt with elsewhere on a regional basis.

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Description: A site response experiment was performed in the basin of Città di Castello (a small town in Central Italy) in May 2001. This study is part of a project on the evaluation of seismic hazard in seismogenic areas funded by the Gruppo Nazionale Difesa dai Terremoti (GNDT). The experiment consisted of a dense fixed transect configuration with most of the stations recording in continuous mode, and several ambient noise measurements both in single station and in array configuration spread over the investigated area. The dense transect was composed of 26 seismic stations in a crosswise configuration with a maximum inter-station distance of 250 m. The stations were deployed in the southern part of the basin, from the eastern bedrock outcrop to the western edge, across the town. About 70 earthquakes were recorded during 10 days of deployment, generally low magnitude or regional events. We located 23 earthquakes and 17 of them were located using the waveform similarity approach at 4 stations outside the target area. These 4 stations were part of a dense temporary seismic network involved in a previous experiment of the same project, aimed at performing a high-resolution picture of the local seismicity. Delay analysis on the recorded waveforms allowed us to infer the basin geometry at depth and estimate the S-wave velocity of sediments. Moreover, we evaluated relative site response along the E-W transect by performing a standard spectral ratio. Amplification factors up to 9 are found inside the basin; at frequencies above 5 Hz stations closer to the edges show higher amplification, whereas stations located in the middle of the basin, where the alluvial sediments are thicker (CD11-CD14), show higher amplification below 5 Hz. We considered the average amplification in two frequency bands (1-5 Hz and 5-10 Hz), representative of the resonance frequency for 2-3 storey buildings and 1 storey houses,respectively. Our results suggest that the potential hazard for 2-3 storey buildings is higher in the center of the basin (amplification factor up to 6), and for 1 storey houses is higher at the edges (amplification factor up to 5).

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Description: To verify the results of seismic microzoning and to improve techniques, the damage data of past destructive earthquakes is an important key reference. The damage data of the 1923 Kanto, Japan, earthquake in the epicentral region are collected and compiled to produce the most reliable and detailed damage map. The damage map is compared with the results from the existing damage assessment and is used to discuss revision of the site amplification evaluation.

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Description: The Gubbio Basin is a 22 km long, 4 km wide depression located within the North-Central Apennines fold-andthrust belt. The basin is bounded to the east by the Gubbio Fault, a W-dipping, normal fault dissecting a large Jurassic-Oligocene anticline. Although located along one of the main seismogenic zones of the Peninsula, both historical and instrumental is seismicity is limited with the only exception for the 29 April 1984, Ms 5.3 earthquake, which occurred about 10 km southwest of the basin. Most of the literature attributes this seismicity to the Gubbio Fault. New geomorphic and geologic investigations based on field and aerial photo surveys and DEM analyses provide new insights on the active faulting in the area and are used to infer potential seismogenic sources. Limited evidence of ongoing deformation along the surface expression of the Gubbio Fault was found, possibly because of low rates of deformation versus fast erosional processes. The western side of the basin appears to be controlled by an east-dipping normal fault, antithetic to the Gubbio Fault. Standard dislocation modeling was used to understand the role played by the Gubbio Fault and its antithetic. The Gubbio Fault was divided into a high-angle section above 3.5 km and a low-angle section between 3.5 and 6 km depth. Based on different tests we conclude that both sections of the Gubbio Fault as well as the antitethic fault contributed to the present setting of the basin. At present the antithetic fault appears to be the most effective in producing a geomorphic signature and controlling the basin width. The high-angle Gubbio Fault played a major role in the basin growth but now its activity rate appears minor. Because of the characteristics and location of the 1984 earthquake, the low-angle Gubbio Fault is assumed to be presently active and seismogenic. Based on the integration of geologic, geomorphic and seismological data we suggest that the low-angle Gubbio Fault is formed by two individual sources capable of M 5.3-5.9 earthquakes. The southern source ruptured in the 1984 earthquake while the northern source did not rupture recently nor historically.

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Description: Based on the indicative modelling, the changes in Coulomb failure function (?CFS) suggest that the W-HV segment and the T-P segment could be stable in at least the future 300 years and 190 years respectively, for these periods should be needed to accumulate the stress released by the M 8.2 Wairarapa earthquake, assuming that there is no influence from other sources, the earthquake did not alter the failure threshold, and that failure is a fairly deterministic process. The results also show that the influence on the W-HV segment and T-P segment of the Wellington Fault caused by the 1855, M 8.2 Wairarapa earthquake is significant considering that the average fault rupture recurrence interval on the Wellington Fault is about 500-770 years. With our present understanding of the Wellington and Wairarapa faults, it can be concluded that the 1855 Wairarapa earthquake retarded earthquake occurrence on the W-HV segment and the T-P segment of the Wellington Fault. Thus the seismic hazard in the Wellington region may be over-estimated.

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Description: An analytical approach to estimate the relative contribution of the fluid pressure and tectonic stress in hydrothermal/ volcanic areas is proposed assuming a Coulomb criterion of failure. The analytical procedure requires the coefficient of internal friction, cohesion, rock density, and thickness of overburden to be known from geological data. In addition, the orientation of the principal stress axes and the stress ratio must be determined from the inversion of fault-slip or seismic data (focal mechanisms). At first, the stress magnitude is calculated assuming that faulting occurs in 'dry' conditions (fluid pressure=0). In a second step, the fluid pressure is introduced performing a grid search over the orientation of 1) fault planes that slip by shear failure or 2) cracks that open under different values of fluid pressure and calculating the consistency with the observed fault planes (i.e. strike and dip of faults, cracks, nodal planes from focal mechanisms). The analytical method is applied using fault-slip data from the Solfatara volcano (Campi Flegrei, Italy) and seismic data (focal mechanisms) from the Vesuvius volcano (Italy). In these areas, the fluid pressure required to activate faults (shear fractures) and cracks (open fractures) is calculated. At Solfatara, the ratio between the fluid pressure and the vertical stress ?is very low for faults ( ?=0.16) and relatively high for cracks ( ?=0.5). At Vesuvius, ?=0.6. Limits and uncertainties of the method are also discussed.

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Description: Paleoseismological analyses have been performed in the Central Apennines along faults showing geomorphological evidence of Late Quaternary activity and characterised by the absence of historical seismicity. Three trenches were made along the Mt. Vettore Fault, across a scarp on a Late Pleistocene-Holocene alluvial fan. The youngest displacement event (E1) occurred after 4155-3965 years BP and before the 6th-7th century A.D., a previous event (E2) occurred between 5940-5890/5795-5780 years BP and 4155-3965 years BP, while the oldest event (E3) occurred between 18.000-12.000 years BP and 5940-5890/5795-5780 years BP. One trench was excavated across the Laga Mts. Fault which gave evidence for two displacement events after 8320-8150 years BP. The minimum vertical slip rate estimated through the paleoseismological analysis of the Mt. Vettore Fault is 0.11-0.36 mm/yr, while the minimum slip rate along the Laga Mts. Fault is 0.12 mm/yr. The paleoseismologically inferred recurrence interval is not longer than 4690 years for the Mt. Vettore Fault and not longer than 7570 years for the Laga Mts. Fault, while the minimum elapsed times since the last activation are 1300 and 800 years for the two faults, respectively. The evaluation of the former elapsed time was based on paleoseismological data, while the estimation of the latter was based on the absence of historical earthquakes which may have been caused by the Laga Mts. Fault and on the completeness of the historical catalogues for the large magnitude events in the last eight centuries. Based on the length of the fault at the surface, earthquakes with M 6.5 and 6.6 may be expected from the activation of the Mt. Vettore and Laga Mts. faults, respectively.

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