THE ACCELEROMETRIC NETWORK OF THE INDES-MUSA PROJECT IN THE KALOCHORI AREA: CONFIGURATION, DOCUMENTATION AND PRELIMINARY DATA INTERPRETATION

Ένα δίκτυο επτά επιταχυνσιογράφων στην επιφάνεια του εδάφους και σε κατασκευές εγκαταστάθηκε πρόσφατα στην ευρύτερη περιοχή Καλοχωρίου, δυτικά της Θεσσαλονίκης, στο πλαίσιο του ερευνητικού έργου INDES-MUSA ως τμήμα πολυπαραμετρικού δικτύου καταγραφής της σεισμικής κίνησης και της εδαφικής υποχώρησης της περιοχής. Το δίκτυο περιλαμβάνει σταθμούς εγκατεστημένους στην επιφάνεια του εδάφους και στην κορυφή τυπικών κατασκευών εντός αστικών υποσυνόλων καθώς και ένα σταθμό ελευθέρου πεδίου. Όλοι οι σταθμοί έχουν τεκμηριωθεί καταλλήλως, λαμβάνοντας υπόψη τα ιδιαίτερα χαρακτηριστικά της κάθε εγκατάστασης καθώς και τα χαρακτηριστικά της εδαφικής δομής, όπως αυτά εκφράζονται από την κατανομή με το βάθος της ταχύτητας διάδοσης των διατμητικών κυμάτων σε κάθε θέση. Παρουσιάζονται καταγραφές του δικτύου επιταχυνσιογράφων από τριαντά εννιά σεισμούς και δίνεται η διαδικασία διόρθωσης που εφαρμόστηκε στις πρωτογενείς χρονοϊστορίες επιτάχυνσης κατά το στάδιο επεξεργασίας και αποθήκευσης των σημάτων. Τέλος, παρουσιάζονται προκαταρκτικές συγκρίσεις τιμών μέγιστης εδαφικής επιτάχυνσης μεταξύ σταθμών εντός οικιστικής ζώνης και ελευθέρου πεδίου καθώς και συγκρίσεις φασματικών λόγων οροφής κατασκευών και βάσης με σκοπό την προκαταρκτική εκτίμηση των θεμελιωδών δυναμικών χαρακτηριστικών των ενοργανωμένων κατασκευών. Τα παραπάνω δεδομένα καταγραφών και τεκμηρίωσης είναι διαθέσιμα μέσω της διαδικτυακής πλατφόρμας Web-GIS του έργου INDESMUSA. A network of seven accelerometric stations on both ground surface and structures has been recently installed, as part of a multi-sensor network for monitoring seismic motion and ground subsidence in the broader area of Kalochori, west of Thessaloniki in Northern Greece, within the INDES-MUSA project. This network includes ground installations within the urban area, structural stations on top of structures and a freefield station away from the building stock. The documentation of stations is presented including shear wave velocity profiles of the subsoil at each location. A set of thirtynine earthquakes recorded so far by the accelerometric network is reported, followed by data processing procedures performed in the acquired waveforms. Comparisons of the processed earthquake recordings are presented referring to (a) the urbanground and the free-field stations in terms of peak ground acceleration, indicating amplification trends of ground motion, and (b) the structural and the nearby urban ground stations by means of top-to-base ratios in the frequency domain, towards a preliminary identification of the fundamental vibrational characteristics of the instrumented structures. The processed acceleration data are available through the INDES-MUSA Web-GIS portal

USING GIS AND EARTHQUAKE SCENARIOS FOR THE ASSESSMENT OF EMERGENCY RESPONSE IN CASE OF A STRONG EARTHQUAKE. AN APPLICATION IN THE URBAN AREA OF THESSALONIKI, GREECE

The aim of this paper, which is part of the M.Sc Thesis of the first author, is an initial attempt for the assessment of the emergency response through the road network of the Urban Area of Thessaloniki (UAT) after a strong earthquake. The areas of the road network that are to become inaccessible either due to partial collapse of buildings or due to destruction of the road axes by rupture zones, are detected. The inaccessible parts are determined for the cases of three earthquake scenarios using the values of the Peak Ground Acceleration (PGA), which were calculated for about 6000 points over the UAT, as well as spatial overlay tools of a GIS. In the end, by applying network analysis and according to the situation of the network after the earthquake, the possibility of movement of the fire engines and ambulances was studied and least cost routes from ambulance stations to UAT hospitals were tracked

A geophysical survey in the archaeological site of Archontiko, Yannitsa

The ancient settlement of Archontiko is 4.5 km NW of ancient Pella in North Greece (Figure 1). The findings showed that the area was first occupied by the end of the Iron Age, i.e. 650-550 B.C. Also, showed that the topographic table of Archontiko was a major settlement of the Yannitsa province due to its concessive position by the main roads of Macedonia (Chrysostomou A. and Chrysostomou P., 1993). At the upper layers of the ruins, findings of the Roman and Byzantine times were also unearthed. The geophysical methods have been used in order to detect and map antiquities in various sites in Greece (e.g., Tsokas et al., 1994; 1995; Sawaidis et al., 1999). The resistivity mapping employing the twin probe array, the total magnetic field variations, the airborne photos and the Ground Probing Radar are the most popular methods in this respect. However, almost all geophysical methods can be used to tackle specific problems. From 1992 till 1994, many geophysical surveys were carried out in the area of Archontiko to collect mainly magnetic data. Resistivity measurements were also conducted in a small part of the area. The data presented in this study cover the northern side of the topographic table of Archontiko and they were collected during two campaigns during the summer of the years 1992 and 1993 (Figure 2)

A method for estimating the origin time of an ensuing mainshock by observations of preshock crustal seismic deformation

Observations on accelerating crustal deformation due to the generation of intermediate magnitude preshocks in the Aegean area are used to propose a method for prediction of the origin time of an ensuing mainshock. The method is based on a precursory seismic excitation that occurs in the preshock region at a time correlated to the origin time of the oncoming mainshock. The uncertainty in this prediction is of the order of ± 1.5 years with relatively high confidence ('90%)

Site effect estimation through site characterization from ambient noise recordings,

Site effect assessment is an important step in seismic risk mitigation. There is therefore a drastic need for co proxies to site effects estimates. In that context, a new promising approach was proposed, using the time-avera over the top z meters with z varying form 5, 10, 20 and 30 meters (Vsz) and the fundamental resonance frequen two-parameters characterization of a site. Then to assess site effect, a Site Amplification Prediction Equat completely defined by these two parameters was build-up based on Japanese data from the KiK-Net network. Thu to be validated using other dataset. For that aim the EUROSEIS-test data is a suitable one. The EUROSE sedimentary basin in northern-Greece that has been thoroughly investigated through grants from the European C mainly to study site effects. Fourteen accelerometric stations have been installed since 1995, that to date recorded 100 events. After a review of the main available information over the EUROSEIS-test, we end up with a poor Vs for some of the accelerometric stations. Thus eight accelerometric stations were selected for noise array me surveys to provide more details information about Vsz and f0 parameters. The noise array technique has been pro decades ago but its development is still in progress, particularly regarding the inversion step. Different approaches el al. 2009, Renalier et al. 2009) were tested in this study to provide Vsz. These two inversion strategies provide Vsz for z equals to 10, 20 and 30 meters. With the resulting Vsz and f0 from noise analysis, a validation-test of th SAPE was realized. The results of such a comparison are encouraging and indicate as well limitations of the SAP It is a promising tool for engineering and seismic risk management

Empirical evaluation of microtremor H/V spectral ratio

The objective of this work is to perform a purely empirical assessment of the actual capabilities of the horizontal-to-vertical (H/V) spectral ratio technique to provide reliable and relevant information concerning site conditions and/or site amplification. This objective has been tackled through the homogeneous (re)processing of a large volume of earthquakes and ambient noise data recorded by different research teams in more than 200 sites located mainly in Europe, but also in the Caribbean and in Tehran. The original recordings were first gathered in a specific database with information on both the sites and recorded events. Then, for all sites close to an instrumented reference, average site-to-reference spectral ratios (“spectral ratio method” (SSR)) were derived in a homogeneous way (window selection, smoothing, signal-to-noise ratio threshold, averaging), as well as H/V ratios (“HVSRE–RF”) on earthquake recordings. H/V ratios were also obtained from noise recordings at each site (either specific measurements, or extracted from pre- or post-event noise windows). The spectral curves resulting from these three techniques were estimated reliable for a subset of 104 sites, and were thus compared in terms of fundamental frequency, amplitude and amplification bandwidth, exhibiting agreements and disagreements, for which interpretations are looked for in relation with characteristics of site conditions. The first important result consists in the very good agreement between fundamental frequencies obtained with either technique, observed for 81% of the analyzed sites. A significant part of the disagreements correspond to thick, low frequency, continental sites where natural noise level is often very low and H/V noise ratios do not exhibit any clear peak. The second important result is the absence of correlation between H/V peak amplitude and the actual site amplification measured on site-to-reference spectral ratios. There are, however, two statistically significant results about the amplitude of the H/V curve: the peak amplitude may be considered as a lower bound estimate of the actual amplification indicated by SSR (it is smaller for 79% of the 104 investigated sites), and, from another point of view, the difference in amplitude exhibits a questioning correlation with the geometrical characteristics of the sediment/basement interface: large SSR/HV differences might thus help to detect the existence of significant 2D or 3D effects.Published75-1084.1. Metodologie sismologiche per l'ingegneria sismicaJCR Journalreserve

NERA project - Deliverable D11.4: Array measurements

The aim of this Task is to present the seismological data and some preliminary empirical results related to two deployed specific arrays; (a) the Argostoli seismological array and (b) the Fucino seismological array. Both experiment arrays provided high quality data that along with corresponding geological and geophysical measurements may serve to critical evaluation of site effects and basin effects. In addition, work on modelling of basin effects may be significantly benefited by the observed acquired in both sites. Given that the analyses of the data obtained during the aforementioned experimental arrays will be performed in close link with activity of NERA-JRA3, the following goals are set: To investigate the link between ground motion spatial variability, strains, seismic wavefield and subsurface properties To compare numerical estimates of ground strain with actual measurements To investigate the capability of estimating ground strains from noise correlation studies. In order to organize and accomplish the work according to the initial schedule, several meetings (actual or/and Skype) among the participants took place during the 2nd year of the NERA-JRA1 project. Minutes of these meetings are given in Appendices 1, 2, 3 and 4.Network of European Research Infrastructures for Earthquake Risk Assessment and Mitigation Project, Seventh Framework Programme EC project number: 262330Published4T. Sismologia, geofisica e geologia per l'ingegneria sismic