THE SAMOTHRACE EARTHQUAKE OF MAY 2014 AND THE DISPLACEMENTS ESTIMATIONS USING PERMANENT GPS STATIONS DATA

Η συμβολή των δικτύων GPS στην παρακολούθηση σεισμικών φαινομένων είναι σημαντική καθώς παρέχει άμεση γεωμετρική πληροφορία στο γήινο φλοιό χρησιμοποιώντας δορυφορικές παρατηρήσεις. Στη παρούσα μελέτη εξετάζονται οι μετακινήσεις στη θέση των μόνιμων σταθμών GPS, που προέρχονται από έντονα σεισμικά φαινόμενα στη περιοχή του Β. Αιγαίου μετά τον έντονο σεισμό στις 24 Μαΐου του 2014. Οι μετακινήσεις στο οριζόντιο επίπεδο μετά το σεισμό για το νησί της Σαμοθράκης εκτιμήθηκαν σε 9.4 cm και για το νησί της Λήμνου σε 5.2 cm αντιστοίχως. Διάστημα μελέτης επτά ημερών ήταν ικανό για να φανεί ότι η παραμόρφωση εξελίχθηκε σταδιακά σε διάστημα δύο ημερών.The contribution of GPS networks in monitoring seismic events is important because they can provide a direct geometrical information on the Earth's crust using satellite observations In this study position displacements of permanent GPS stations are determined due to intense seismic events in the North Aegean area after the strong earthquake on May 24, 2014. The horizontal coseismic displacements for the Samothrace Island were estimated at 9.4 cm and for Lemnos Island at 5.2 cm respectively. A study period of seven days was enough to show that the deformation evolved into two days

IMPROVING THE RESOLUTION OF SEISMIC HAZARD ESTIMATES FOR CRITICAL FACILITIES: THE DATABASE OF GREEK CRUSTAL SEISMOGENIC SOURCES IN THE FRAME OF THE SHARE PROJECT

SHARE (Seismic Hazard Harmonization in Europe) European project aims at delivering measurable progress in all steps leading to a harmonized assessment of seismic hazard in Europe -in the definition of engineering requirements, in the collection and analysis of input data, in procedures for hazard assessment, and in engineering applications. In this frame, a database of the shallow (crustal) seismogenic sources for the broader Aegean Region is developed The Greek database focuses on three major goals: (i) the systematic collection of all available information concerning neotectonic, active and capable faults as well as broader seismogenic volumes; (ii) the critical analysis of the data and the quantification of the principal seismotectonic parameters of the various sources and the associated degree of uncertainty; (iii) to supply an integrated view of potentially damaging seismogenic sources for a better SHA in Greece. The informatic framework of the database follows that used for the Italian DISS. In this paper we present the state-of-the-art of the Composite Seismogenic Sources (CSS) for the broader Aegean region. The Aegean Region is among the most tectonically active areas of the Mediterranean realm and has the highest seismicity both in terms of frequency of events and magnitudes. The tectonic regime is rather complex producing earthquakes with many different orientations of nodal planes and a large variety of fault types both in terms of dimension and kinematics. It is not always straightforward to correlate seismicity with the causative fault(s). This is mainly due to two reasons: firstly, several crustal sectors of the Aegean, where historical or instrumental epicentres are located, are affected by a dense fault population bearing evidences of recent activity but with badly defined seismotectonic behaviour. Secondly, large sectors of the broader Aegean Region are covered by the sea, therefore lacking crucial field and direct observations. In the latter case, the typical geological approaches are generally replaced with geophysical and seismological investigations (detailed bathymetry, seismic profiles, microseismicity, focal mechanisms, etc.), which can be proved very useful. A first attempt to create a similar database for the Greek territory was carried out during the EU project FAUST (2001), where ca. 50 earthquake-related sources have been included. In contrast, the most recent and the most complete map of capable faults in Greece and the broader Aegean Region has been compiled by Other attempts have been performed in the past, but all of them were lacking in both fault and data completeness. For example, simple map compilations cannot provide much information except the geographical location and few geometrical characteristics of the faults, like length and dip direction. On the other hand, fault catalogues generally lack important additional data, like geometric, kinematic and seismological ones. In order to bypass the above problems and to make the database a continuously updatable open-file, the choice of a GIS-based software was crucial. For our purpos-232 GNGTS 2011 SESSIONE 2.

PALAEOSEISMOLOGICAL INVESTIGATION OF THE GYRTONI FAULT (THESSALY, CENTRAL GREECE)

Two paleoseismological trenches were excavated across the Gyrtoni Fault in NE Thessaly and studied in order to understand the recent seismotectonic behavior of this structure. Twenty five fluvial-colluvial sediment and pottery samples from both the upthrown and the downthrown fault blocks were investigated. Optically Stimulated Luminescence (OSL) dating has been applied to date both sedimentary depositspalaeosoils and pottery fragments. Paleoseismological analysis of the two trenches indicates evidence of three surface faulting events in the time span between 1.42 ±0.06 ka and 5.59 ± 0.13 ka. The observed vertical displacement per event of ~0.50 m corresponds to an Mw 6.5 ± 0.1 earthquake. An average fault slip rate of 0.41 ± 0.01 mm/yr and an average recurrence of 1.39 ± 0.14 ka for earthquakes were estimated. The results documented the activity of the fault and since the return period from the most recent event (minimum age 1.42 ± 0.06 ka) has expired, the possibility for reactivation of this active structure in the near future should be included in Seismic Hazard Assessment

Seismic hazard for the Trans Adriatic Pipeline (TAP). Part 2: broadband scenarios at the Fier Compressor Station (Albania)

AbstractTo ensure environmental and public safety, critical facilities require rigorous seismic hazard analysis to define seismic input for their design. We consider the case of the Trans Adriatic Pipeline (TAP), which is a pipeline that transports natural gas from the Caspian Sea to southern Italy, crossing active faults and areas characterized by high seismicity levels. For this pipeline, we develop a Probabilistic Seismic Hazard Assessment (PSHA) for the broader area, and, for the selected critical sites, we perform deterministic seismic hazard assessment (DSHA), by calculating shaking scenarios that account for the physics of the source, propagation, and site effects. This paper presents a DSHA for a compressor station located at Fier, along the Albanian coastal region. Considering the location of the most hazardous faults in the study site, revealed by the PSHA disaggregation, we model the ground motion for two different scenarios to simulate the worst-case scenario for this compressor station. We compute broadband waveforms for receivers on soft soils by applying specific transfer functions estimated from the available geotechnical data for the Fier area. The simulations reproduce the variability observed in the ground motion recorded in the near-earthquake source. The vertical ground motion is strong for receivers placed above the rupture areas and should not be ignored in seismic designs; furthermore, our vertical simulations reproduce the displacement and the static offset of the ground motion highlighted in recent studies. This observation confirms the importance of the DSHA analysis in defining the expected pipeline damage functions and permanent soil deformations

Review of the accuracy of Single Core Equivalent Thermal Model (SCETM) for Offshore Wind Farm (OWF) cables

Cables intended to interconnect OWFs with the mainland are currently treated as SL-type (Separate Lead) cables by IEC 60287. A SCETM is implied, i.e. a thermal model accounting for 1-D (radial) heat transfer only. While this approach is expected to be reasonable when smaller cables are rated, the 1-D representation is less valid in larger cable sizes. This paper uses 2-D finite element models to reveal certain weak points of the representation of the thermal resistances in the existing SCETM. For constant losses, the IEC SCETM seems to underestimate the temperature by up to 8oC. Suitable replacement formulae are proposed which could improve the accuracy of the SCETM. Finally, the issue of non-solid fillers is considered and modelling guidelines are given