Akademik Veri Yönetim Sistemi
Teknik Rapor, ss.1-28, 2020
A strong earthquake (Mw=6.6 AFAD*, Mw=6.9** KOERI, Mw=7.0 USGS***) of normal faulting striking about E-W occurred on October 30, 2020 (11:51 UTC) in between offshore Seferihisar (Izmir, Turkey) and Samos Island (Greece). The earthquake generated a tsunami that affected an area in the Aegean Coast of Turkey from Cesme Alacati in the northwestern part to Gumuldur coast in the southeastern part. Immediately after the event, a post-event field survey was performed on 31 October and 1 November 2020 by a team of seven people (A.C. Yalciner, G.G. Dogan, E. Ulutas and O. Polat, A. Tarih, E. R. Yapar and E. Yavuz) from METU, Kocaeli University, Dokuz Eylul University and Istanbul Metropolitan Municipality. The Turkey coast survey area covers mainly three parts: i) Alacati and Zeytineli regions in the Northwestern, ii) Sigacik Bay and Akarca region in Seferihisar coast in the North, and iii) Tepecik and Gumuldur regions in the Northeastern with respect to the earthquake epicenter. The team feels deep sorrow and express their condolences to the people for the loss of life and property in Izmir, Turkey and Greece.
Unfortunately, the tsunami was not recorded by any tide gauge located along the Turkish Coast of the Aegean Sea. Therefore, findings from the post-event survey have gained much more importance as the main documentation of sea level variations. The main objectives of this survey are to document the tsunami effects along the coast, obtain any available data on the observed coastal amplitudes and inundation extent, take pictures and audiovisual recording before they were cleaned, interview the eyewitnesses and to understand and explain the event in detail.
According to the findings in this field survey and eyewitness reports, the most impacted areas were Sigacik Marina, Sigacik Bay and Akarca region located in a 30 km distance to the epicenter in the northern direction. The maximum inundation distance reached 320 m in Akarca, where 20 boats were sunk in a small fishery port, as reported by the head of the port. The flow depth at this location was measured as 1.86 m. There was a splash height of 1.9 m recorded on a vertical wall of a highly damaged house just near the shore. The more to the southeastern coast after Akarca region, the less impacts were observed. There was almost no significant inundation water motion after Gumuldur. The tsunami impacts highly decreased after the cape of v shape peninsula between Tepecik and Gumuldur.
In the northeastern part, Alacati and Zeytineli, the maximum inundation was observed along Alacati Azmak measured as 1300 m. The maximum runup was measured as 1.9 m on the palm trees 50 m away from the coastline in Zeytineli region.
To summarize, our findings show that in small bays with narrow entrances, the tsunami was much amplified and the impacts on these coast were more severe. The region contains many streams (called Azmak in the local language) in the bays, which increases the potential of tsunami inundation and damage as also experienced in this event. Another important point is the remarkable increase in the awareness of the people who mostly moved away from the shore after noticing the sea withdrawal. However, unfortunately, a victim, who could not resist the strong current generated and died, was reported. After the 2017 Bodrum-Kos tsunami, the Aegean Sea with its high seismic mobility and this event once more reminded considerable tsunami potential in the eastern Mediterranean.