Search

The Northern Thessaly Basin in central Greece ranks amongst the most well pronounced extensional (graben) basins in the backarc Aegean Sea region, with well-mapped faults having an ∼E–W orientation, compatible with the ongoing predominant ∼N–S extension. The southern margin of the basin is bounded by major faults associated with strong (M 6 to M 7) earthquakes, whereas along its northern margin, strong events are more scarce, in the documented catalogues. Along this northern margin, a weak, albeit persisting foreshock activity, culminated within 3 d, to an M w 6.3 earthquake on 3 March 2021 associated with a 15-km-long NE dipping fault segment. It was followed the next day, by the second M w 6.0 main shock associated with a 13-km-long NE dipping fault segment and 9 d later by an M w 5.5 earthquake associated with an 8-km-long SW dipping fault segment, with its aligned epicentres, showcasing the cascade type activation of adjacent fault segments. The sequence, evolved to be very productive, with aftershocks extending ∼50 km along a ∼NW–SE trending narrow seismic zone. All events indicate pure normal faulting, with an NNE–SSW oriented extensional axis, oblique to our previous consensus of the prevalence of ∼N–S extension. This observation documents that inherited fault fabric can be reactivated within the modern tectonic stress field. We use high-quality seismological data, alongside Interferometric Synthetic Aperture Radar (InSAR) methodology and Global Navigation Satellite System (GNSS) data, to study the temporal and spatial evolution of the sequence, and to provide inferred kinematic models that describe the complexity of the seismic process, in terms of heterogeneous slip distribution, activated fault planes, fault geometry and displacement field. Cross-sections show that the activity defines the crustal seismogenic layer at depths between 5 and 10 km, associated with low-angle fault segments dipping to the NE. Other faults, both antithetic and secondary ones, appear active and accommodated aftershocks clusters. Using our preferred finite fault source model, we calculated the changes of Coulomb failure stress on the neighbouring faults. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the Geological Society of Greece is the property of Geological Society of Greece and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The broader Corinth Gulf region is characterized by a notable active tectonic regime, associated with multiple active fault zones. The continuous N-S extensional tectonics of the area is responsible for the roughly E-W trending active normal fault zones, while individual fault segments are associated with seismic events. Satellite geodesy is a qualitative and quantitative means of estimating the tectonically active setting, based on the recorded motions. The study area is monitored by 14 permanent GPS/GNSS stations, collecting primary geodetic data for a 7-year time period (2008-2014). A 30-sec observation rate was performed, resulting in the extraction of the GPS/GNSS velocity values. The primary geodetic data were processed by applying the triangulation methodology, based on the combination of three different GPS/GNSS stations data, which were considered as the triangle vertices. Triangulation methodology led to the construction of 26 different triangles, while for each of them a series of parameters was determined. In particular, the extracted parameters are: a) Maximum Horizontal Extension, b) Total Velocity, c) Maximum Shear Strain and d) Area Strain. The extracted results are expected to approach, qualitatively and quantitatively, the interpretation of the tectonic regime, as well as to determine new, seismic-related, tectonic features. [ABSTRACT FROM AUTHOR]

In this study, we show how the Global Navigation Satellite System (GNSS)-derived vertical velocities contribute to the correction of tide gauge (TG) measurements used for the sea level rise estimation in Greece. Twelve sites with records of local sea level heights are processed in order to estimate their trend. Certain error sources related to TGs, e.g. equipment changes, data noise, may lead to biased or erroneous estimations of the sea level height. Therefore, it would be preferred to follow a robust estimation technique in order to detect and reduce outlier effects. The geocentric sea level rise is estimated by taking into account the land vertical motion of co-located GNSS permanent stations at the Hellenic area. TGs measure the height of the water relative to a monitored geodetic benchmark on land. On the other hand, using GNSS-based methods the vertical land motion can be derived. By means of extended models fitted to the GNSS time-series position, obtained from seven years of continuous data analysis, periodic signals are well described. The synergy of the two co-located techniques results in the correction of TG relative sea level heights taking into account the GNSS vertical velocities and consequently obtaining the conversion to absolute (geocentric) sea level trend. [ABSTRACT FROM AUTHOR]

The project BeRTISS (Balkan-Mediterranean Real TIme Severe weather Service) was launched in September 2017 of the European Territorial Cooperation Programme "Interreg V-B Balkan-Mediterranean 2014-2020" and is co-funded by the European Regional Development Fund (ERDF) and National Funds of the participating countries (Greece, Cyprus, Bulgaria). The main objective of BeRTISS is to develop and establish a pilot transnational severe weather service by exploiting Global Navigation Satellite Systems (GNSS) tropospheric products to enhance the safety, the quality of life and environmental protection in the Balkan‐Mediterranean region. For the implementation of current project, we are producing (in operational basis) atmospheric parameters such as, Zenith Total Delay (ZTD), Precipitable Water (PW) and tropospheric gradients from Global Navigation Satellite Systems (GNSS) data from a dense network located in Greek area.One of the scopes of the present research is the quality check of rinex data which retrieved on an hourly scenario. For that reason, several algorithms have been developed and installed in a local (AUTh) processing data server and special features for editing and quality control have been established, e.g. for multipath analyses (MP) and signal-to-noise ratio (SNR), Sky plots, Satellite Data visibility and a daily report provides additional statistics from those results are created and stored.This presentation, also demonstrates the various features of used QC software for quality control especially for multi-GNSS data. The quality check procedure is linked with project's website and graphical results are depicted under station selection. In addition the proposed strategic quality route plan finalizes the study. [ABSTRACT FROM AUTHOR]

Water vapour plays a key role in some of the most important weather phenomena. It is obviously related to precipitation, but also provides about half the energy to the atmosphere, contributing to atmospheric dynamics, and it is the dominant greenhouse gas. The project BeRTISS (Balkan-Mediterranean Real TIme Severe weather Service) was launched in September 2017 of the European Territorial Cooperation Programme "Interreg V-B Balkan-Mediterranean 2014-2020" and is co-funded by the European Regional Development Fund (ERDF) and National Funds of the participating countries (Greece, Cyprus, Bulgaria). The main objective of BeRTISS is to develop and establish a pilot transnational severe weather service by exploiting Global Navigation Satellite Systems (GNSS) tropospheric products to enhance the safety, the quality of life and environmental protection in the Balkan‐Mediterranean region. For that reason, a creation of a dedicated website (www.bertiss.topo.auth.gr/bertiss) to provide in real-time to the National Meteorological Services, to related scientists and to the public with IWV data and warnings of severe weather events was implemented over the Greek Area. The processing scenario of the tropospheric products (e.g. ZTD, PW/IWV) performed in one-hour time window for over 90 sites in the Hellenic area. The automated GNSS processing performed employing the Bernese v.5.2 software package and several algorithms have been developed and installed in a local (AUTh) processing data server.More specific, the warning–alert system relies on the PostgreSQL database while the Backend is a PHP language algorithm and with a Frontend environment of Bootstrap. The system also, retrieves relevant information from Weather Research and Forecasting (WRF) model which National Observatory of Athens sent to AUTh's server on a daily basis. One of the main characteristics during a period of a severe event is the mass dispatch of emails for each affected GNSS station to many registered clients. During the period of the Mediterranean powerful hurricane called "Zorba" which induces with storm roars across Greece and triggering flooding as it makes its way towards, the Alert system was activated several times for various affected areas. Finally, a main website which will host the relevant information from all the participating countries is under development by Leader Partner (FRC). [ABSTRACT FROM AUTHOR]