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Characteristics of the 2020 Samos earthquake (Aegean Sea) using seismic data

  • S.I. : The M7.0 Samos Island (Aegean Sea) Earthquake of 30th October 2020
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Abstract

The 30 October 2020 Samos earthquake (Mw 7.0) ruptured an east–west striking, north dipping normal fault located offshore the northern coast of Samos Island, previously inferred from the bathymetry and regional tectonics. This fault, reported in the fault-databases as the North Samos and/or Kaystrios Fault, ruptured with almost pure dip-slip motion, in a region where both active extension and strike-slip deformation coexist. Historical information for the area confirms that similar ~ Mw7 events had also occurred in the broader Samos area, though none of the recent (last ~ 300 years) mainshocks appears to have ruptured the same fault. The spatial and temporal distribution of relocated aftershocks indicates triggering of nearby strike-slip and normal fault segments, situated in the areas where static stress has increased due to the mainshock generation. The relocated aftershocks and the slip model indicate that the sequence ruptured the upper crust (mainly the depth range 3–15 km). The top of the rupture plane nearly reached the sea bottom, located at a depth of < 1 km. Slip is confined in mainly two asperities, both located up-dip from the hypocenter and at shallow depths. The average displacement is ~ 1 m and the peak slip is ~ 3.5 m for a shear modulus of 3.2e10 N/m2. While it is difficult to constrain the rupture velocity in the inversions, the model suggests a slow rupture speed of the order of 2.2 km/s. The resolved source duration is ~ 16 s, compatible with the ~ 32 km length of the fault that ruptured.

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Fig. 1

NAFZ: North Anatolian Fault Zone, EAFZ: East Anatolian Fault Zone, DSFZ: Dead Sea Fault Zone, CAFZ: Central Anatolian Fault Zone, TF: Tuz Gölü Fault, IEFZ: İnönü Eskişehir Fault Zone, IBTZ: İzmir-Balıkesir Transfer Zone, MCL: Mid-Cycladic Lineament

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Several off-fault secondary seismicity clusters are depicted with numbered dotted-line ellipses (see text for details). The morphotectonic feature (canyon) associated with clusters 1 and 4 is also depicted with a yellow dashed line in b

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Authors’ contributions

All authors contributed to the study conception and design, to the methodology and data elaboration; AK, CP, AO and AP wrote the first draft of the manuscript and all authors read, reviewed and approved the final manuscript.

Availability of data and material

Digital seismic waveforms were retrieved from the ORFEUS Eida-nodes (orfeus-eu.org), and AFAD [https://deprem.afad.gov.tr/] and are acquired from the following regional networks: HUSN (HL, https://doi.org/10.7914/SN/HL; HT, https://doi.org/10.7914/SN/HT; HA, https://doi.org/10.7914/SN/HA; HP, https://doi.org/10.7914/SN/HP; HI, https://doi.org/10.7914/SN/HI; HC, https://doi.org/10.7914/SN/HC); KOERI (KO, https://doi.org/10.7914/SN/KO), AFAD (TU, doi.org/https://doi.org/10.7914/SN/TU). Catalogue and seismic phase data were collected from the following regional networks: HUSN (HL, https://doi.org/10.7914/SN/HL; HT, https://doi.org/10.7914/SN/HT; HA, https://doi.org/10.7914/SN/HA; HP, https://doi.org/10.7914/SN/HP; HI, https://doi.org/10.7914/SN/HI; HC, https://doi.org/10.7914/SN/HC), AFAD (TU, https://doi.org/10.7914/SN/TU) and KOERI (KO, https://doi.org/10.7914/SN/KO), obtained through the web services of the individual networks and the corresponding EMSC-CSEM online services. The faults from NOA are available at https://zenodo.org/record/4897894#.YT9jI99RUuU. A number of figures were drawn using the Generic Mapping Tools (GMT) software (Wessel and Smith 1998).

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Acknowledgements

We acknowledge the faculty and staff members of several Universities and research Institutes, both in Greece and Turkey, for the careful analysis of the data, the maintenance and operation of the networks.

Funding

AK, CP and ChK acknowledge support by the project “HELPOS—Hellenic Plate Observing System” (MIS 5002697) which is implemented under the Action “Reinforcement of the Research and Innovation Infrastructure”, funded by the Operational Programme "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014–2020) and co-financed by Greece and the EU (European Regional Development Fund). AO and AP acknowledge Middle East Technical University that provided funding for fieldwork. ChK was also partly financed by ESF through the project “Reinforcement of Postdoctoral Researchers—2nd Cycle” (MIS-5033021), implemented by the State Scholarships Foundation (IKY).

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Authors and Affiliations

  1. Department of Geophysics, Aristotle University of Thessaloniki, 54124, Thessaloniki, Greece

    Anastasia Kiratzi, Costas Papazachos & Charis Kkallas

  2. Middle East Technical University, Ankara, Turkey

    Arda Özacar & Eyüp Sopaci

  3. Boğaziçi University, KOERI, Istanbul, Turkey

    Ali Pinar

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  1. Anastasia Kiratzi
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Kiratzi, A., Papazachos, C., Özacar, A. et al. Characteristics of the 2020 Samos earthquake (Aegean Sea) using seismic data. Bull Earthquake Eng 20, 7713–7735 (2022). https://doi.org/10.1007/s10518-021-01239-1

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