• Event Date : 10-30-2020
  • Location: Samos Island, Greece
  • Report Date : 12-31-2020
  • Event Category: Earthquake
  • EQ Magnitude: 7.0
  • Report Number: GEER-069
  • DOI: doi:10.18118/G6H088
  • Event Latitude: 37.8919
  • Event Longitude: 26.8066
  • Team:
    113 contributors    (see report)
    Report Coordinators:    
    K. Onder    Cetin
    George    Mylonakis
    Anastasios    Sextos
    Jonathan P.    Stewart
  • Summary: On 30 October 2020, an M 7.0 earthquake occurred north of Samos Island. The fault rupture caused sudden lowering of the seafloor, which produced a tsunami that mainly impacted nearby Samos Island as well as a series of Anatolian cities along the coast of Seferihisar Bay, with maximum runup and inundation lengths of about 3.8 m and 2500 m, resulting in substantial property losses. The mainshock was recorded by > 200 accelerometers from Turkish and Greek national networks for rupture distances up to 600 km. Overall levels of ground shaking, and their variation with distance, are consistent with expectation from regionally-adjusted global ground motion models. The intensity of ground shaking was near design levels in Samos Island, but well below design levels for reference rock conditions in the Anatolian coastal regions due to large source-site distances (30 to 70 km). Where site conditions were favorable (rock or shallow stiff soils), these ground motions did not damage structures. However, pronounced site effects locally amplified ground shaking at site frequencies near 0.7-1.6 Hz throughout the Izmir Bay region for both stiff and soft soil sites. This amplification was particularly pronounced on soft soils in the Bayrakli district, which led to significant structural damage. The earthquake produced isolated incidents of rockfalls and landslides, mainly in the northern part of Samos Island. We document these ground failures, as well as several “no-ground failure” case histories in Anatolia. Liquefaction was observed in different parts of Samos island, including ports. The emergency responses in Greece and Turkey provided support to residents displaced from their homes. In both regions, educational efforts with local government officials and residents had been undertaken prior to the event that were helpful.
The work of the GEER Association, in general, is based upon work supported in part by the National Science Foundation through the Geotechnical Engineering Program under Grant No. CMMI-1826118. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NSF. The GEER Association is made possible by the vision and support of the NSF Geotechnical Engineering Program Directors: Dr. Richard Fragaszy and the late Dr. Cliff Astill. GEER members also donate their time, talent, and resources to collect time-sensitive field observations of the effects of extreme events.