AZIMUTHAL DEPENDENCE OF THE SEISMIC WAVES AND ITS INFLUENCE IN THE SEISMIC HAZARD ASSESSMENT IN THE AREA OF GREECE

THE DIRECTIVITY AND THE AZIMUTHAL DEPENDENCE OF THE SEISMIC INTENSITIES HAVE BEEN RECOGNIZED AS AN IMPORTANT FACTOR IN STRONG GROUND MOTION. THE AZIMUTHAL DEPENDENT ATTENUATION OF THE SEISMIC INTENSITIES WAS STUDIED BY TWO MODELS, THE AZIMUTHAL ATTENUATION MODEL OF ANELASTIC COEFFICIENT AND THE ANISOTROPIC RADIATION MODEL. BASED ON THESE MODELS, SEISMIC HAZARD ASSESSMENT WAS CARRIED OUTFOR THE AREA OF GREECE. STOCHASTIC SIMULATION WAS APPLIED IN ORDER TO ESTIMATE SYNTHETIC STRONG GROUND MOTIONS.ΕΧΕΙ ΑΝΑΓΝΩΡΙΣΘΕΙ ΟΤΙ Η ΑΖΙΜΟΥΘΙΑΚΗ ΕΞΑΡΤΗΣΗ ΤΩΝ ΣΕΙΣΜΙΚΩΝ ΕΝΤΑΣΕΩΝ ΕΙΝΑΙ ΕΝΑΣ ΣΗΜΑΝΤΙΚΟΣ ΠΑΡΑΓΟΝΤΑΣ ΤΗΣ ΙΣΧΥΡΗΣ ΣΕΙΣΜΙΚΗΣ ΚΙΝΗΣΗΣ. Η ΑΖΙΜΟΥΘΙΑΚΗ ΕΞΑΡΤΗΣΗ ΤΩΝ ΣΕΙΣΜΙΚΩΝ ΕΝΤΑΣΕΩΝ ΜΕΛΕΤΗΘΗΚΕ ΜΕ ΒΑΣΗ ΤΑ ΜΟΝΤΕΛΑ, ΤΗΣ ΑΖΙΜΟΥΘΙΑΚΗΣ ΑΠΟΣΒΕΣΗΣΤΟΥ ΑΝΕΛΑΣΤΙΚΟΥ ΣΥΝΤΕΛΕΣΤΗ ΑΠΟΣΒΕΣΗΣ ΚΑΙ ΤΗΣ ΑΝΙΣΟΤΡΟΠΗΣ ΑΚΤΙΝΟΒΟΛΙΑΣ. ΜΕ ΒΑΣΗ ΤΑ ΔΥΟ ΜΟΝΤΕΛΑ ΑΥΤΑ, ΕΚΤΙΜΗΘΗΚΕ Η ΣΕΙΣΜΙΚΗ ΕΠΙΚΙΝΔΥΝΟΤΗΤΑ ΤΟΥ ΕΛΛΗΝΙΚΟΥ ΧΩΡΟΥ. Η ΣΤΟΧΑΣΤΙΚΗ ΠΡΟΣΟΜΟΙΩΣΗ ΕΦΑΡΜΟΣΘΗΚΕ ΜΕ ΣΚΟΠΟ ΝΑ ΕΚΤΙΜΗΘΟΥΝ ΣΥΝΘΕΤΙΚΕΣ ΚΑΤΑΓΡΑΦΕΣ ΙΣΧΥΡΗΣ ΣΕΙΣΜΙΚΗΣ ΚΙΝΗΣΗΣ

Seismic Hazard in Greece: A Comparative Study for the Region of East Macedonia and Thrace

Greece is located in one of the most seismically active regions in Europe. Many seismic hazard studies have been performed for various sites around Greece, at a regional or local scale. However, the latest national seismic hazard map, currently used for the seismic design of buildings and infrastructure, was published in 2000 and has not been updated since then. In light of recent advances in seismic source and ground motion modeling, the present study focuses on a comparative Probabilistic Seismic Hazard Assessment (PSHA) for the region of East Macedonia and Thrace (EMTH), located in Northern Greece. Various seismic source models are implemented and compared against an updated earthquake catalog to form the necessary source model logic tree. The ground motion logic tree is composed of Ground Motion Prediction Equations (GMPEs), which have been proven suitable for implementation in Greece. PSHA results are presented for the most important cities of East Macedonia and Thrace in a comparative way, which highlights the variability of the seismic hazard among the various seismic source models. An updated seismic hazard map of the study area is proposed, and a comparative disaggregation analysis is performed to estimate the earthquake scenarios with the largest contribution to the seismic hazard

Strong Motion Database for Crustal Earthquakes in Greece and Surrounding Area

An updated Hellenic database of strong ground motion recordings together with the earthquake source properties and the site characterization of the recording stations are described here. The strong motion database consists of 2751 corrected recordings from 497earthquakes of focal depths h<45km and 338 recording stations, with source to site distances up to 300 km, covering the period from 1973-2015. The strong motion recordings were collected from Hellenic Strong Motion Networks operated by the Institute of Engineering Seismology and Earthquake Engineering (ITSAK), the Institute of Geodynamics, National Observatory of Athens (NOA-IG), as well as from the Civil Engineering Department, University of Patras (UPAN). All recordings were processed based on well-established routines and methodologies applied in worldwide strong motion databases such as the PEER, NGA-West2 database. The final database includes epicenter locations, focal depths, moment magnitudes (directly estimated or equivalently derived after a conversion procedure) for a significant number of earthquakes with M>4.5and a number of finite fault plane solutions corresponding to earthquakes with M>6.0. The data is compiled from existing catalogs published by Hellenic and international seismological centers. The properties for each recording station include surface geology, a measured or estimated time-averaged shear wave velocity in the upper 30m (VS30), and information on instrument housing. Out of the 338sites, 75 have in-situ shear wave velocity measurements while for the rest VS30 values are derived from proxy-based relationships based on terrain or geology combined with surface gradient