The major (Mw=7.0) earthquake of 30th October 2020 north Samos Island, Greece: Analysis of seismological and geodetic data

On 30th October 2020, at 11.51 (UTC), a very strong earthquake of magnitude M_w = 7.0 struck north of the Greek island of Samos in the Aegean coast of Turkey, south of Izmir. The epicentre was determined 17km north of Samos, in the Gulf of Ephesus and was felt in many parts of Greece and western Turkey. The geographical coordinates as calculated of the manual analysis of the National Observatory of Athens (http://bbnet.gein.noa.gr/Events/2020/10/noa2020vipzs_info.html) was determined as  φ= 37.9001⁰N, λ=26.8167⁰E at a focal depth at 11.8km. The earthquake triggered a tsunami that flooded the coastal district of Seferihisar (Turkey), Cesme, Izmir and the port of Samos (Greece). In the next 8 minutes after the detection of the earthquake, tsunami bulletins were issued to national focal points by the Tsunami Service Providers accredited by UNESCO’s IOC Intergovernmental Coordination Group for the Tsunami Early Warning and Mitigation System in the North-eastern Atlantic, the Mediterranean and connected seas (ICG/NEAMTWS). Greece and Turkey were put on Tsunami Watch (highest level of alert). In Seferishar the tsunami swept away many boats in the marina and the water level reached 1.5 meters causing damage to shops.

Three hours later, 15:14 (UTC) a second strong event (M_w = 5.3) occurred in the same region some kilometres south of the main earthquake (φ=37.8223⁰N,λ=26.8652⁰E, http://bbnet.gein.noa.gr/Events/2020/10/noa2020viwsi_info.html). By the end of the same day that the earthquake took place, there were 65 aftershocks while a total of 576 aftershocks up to 31/12 with magnitude greater than 1.0. For the aftershocks with 3.7<M_L<7.0 we applied the moment tensor inversion to determine the focal mechanism, the Seismic Moment (M₀) and the Moment Magnitude (Mw). For this purpose, 3–component broadband seismological data from the Hellenic Unified Seismological Network (HUSN) at epicentral distances less than 3˚ were selected and analysed. The preparation of the data, includes the deconvolution of instrument response, following the velocity was integrated to displacement and finally the horizontal components rotated to radial and transverse. Finally, an extensive kinematic analysis from data provided by two private sector companies networks was done.

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Athanassios Ganas, Zafeiria Roumelioti, Vassilios Karastathis, Konstantinos Chousianitis, Alexandra Moshou, Evangelos Mouzakiotis. The Lemnos 8 January 2013 (Mw=5.7) earthquake: fault slip, aftershock properties and static stress transfer modeling in the north Aegean Sea J Seismol (2014) 18:433–455 DOI 10.1007/s10950-014-9418-3

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