Preliminary Observations After the 2020 Aegean Sea Earthquake

Abstract

The October 30, 2020 Aegean Sea Earthquake occurred with a magnitude of M6.6 and caused significant damages across the city of Izmir, Turkey. Specifically, this paper presents the preliminary observation results based on; ground motion properties, local site conditions, code-based design procedures, and the structural damage mechanisms. In order to achieve this purpose, critical spectral characteristic of strong ground motion records were evaluated in advance. Then, the variables given in code-based design results were investigated based on base shear to structural weight ratio. Local site effects were considered by comparing the spectral amplitudes obtained for different strong ground motions recorded from stations with different soil characteristics (i.e. the shear wave velocity (VS30) averaged over top 30m of the soil profile). Primary temporal distributions of recorded earthquake sequences followed by the mainshock were detailed and the directionality characteristics of the strong ground motion recorded after the mainshock were summarized. Moreover, observed damage patterns in buildings are discussed and possible reasons were identified in terms of critical structural properties. Preliminary results generally represent the effect of local soil characteristics on the amplification of spectral properties.

Keywords

• 2020 Aegean Sea Earthquake
• Local site properties
• Structural damage
• Strong ground motion records

PRELIMINARY OBSERVATIONS AFTER THE 2020 AEGEAN SEA EARTHQUAKE

Abstract

30 Ekim 2020 tarihinde Ege Denizi’nde meydana gelen M6.6 büyüklüğündeki deprem özellikle İzmir ve çevresinde önemli hasar ve yıkımlara neden olmuştur. Çalışma kapsamında, yer hareketi özellikleri, yerel zemin koşullarının bina hasarları üzerindeki etkisi, mevcut binalarda kullanılan tasarım yaklaşımları ve yapısal hasar mekanizmaları gibi temel konulara bağlı olarak, deprem sonrasında gerçekleştirilen ilk gözlem sonuçlarına yer verilmiştir. Bu amaçla, öncelikle kuvvetli yer hareketi kayıtlarına ait kritik spektral parametreler belirlenmiştir. Farklı yıllarda yürürlükte olan tasarım yönetmeliklerindeki esaslar dikkate alınarak, tasarım değişkenlikleri taban kesme kuvveti ile bina ağırlığı arasındaki oran dikkate alınarak incelenmiştir. Yerel saha koşullarının etkisi, farklı zemin koşullarına sahip (örn, zemin profilinin ortalama 30m seviyesindeki kayma dalgası hızı, VS30) istasyonlardan elde edilen kuvvetli yer hareketi kayıtlarına ait spektral büyüklüklerin karşılaştırılmasıyla dikkate alınmıştır. Ana deprem sonrasında belirli bir süre içerisinde bölgede gözlemlenen deprem serileri incelenmiş ve ana deprem kaydına ait yönlülük karakteristiği farklı periyotlar için incelenmiştir. Binalarda meydana gelen hasar dağılımları üzerine tespitlerde bulunulmuştur. Elde edilen ilk gözlem sonuçları genel olarak, bölgedeki farklı zemin özelliklerinin kuvvetli yer hareketi kayıtlarına ait spektral değerlerinde yükseltgenmelere yol açabildiği belirlenmiş ve binalarda oluşan yapısal hasarların olası nedenleri üzerine tartışmalara yer verilmiştir.

Keywords

• 2020 Ege Denizi Depremi
• Yerel zemin koşulları
• Kuvvetli yer hareketi kayıtları

References

1. AFAD (2020a), -the October 30, 2020 Aegean Sea, off the coast of Seferihisar (İzmir) Mw6.6 Earthquake Preliminary Report (In Turkish)- Disaster and Emergency Management of Turkey, Ankara, Turkey. Available online: https://deprem.afad.gov.tr/, [Accessed: October 30, 2020].
2. EMSC (2020), -the Earthquake of October 30, 2020, M6.7 Preliminary Report-European Mediterranean Seismological Centre (EMSC), Available online: https://www.emsc-csem.org/, [Accessed: October 30, 2020].
3. BBC (2020), -Earthquake hits Greece and Turkey, bringing deaths and floods-, BBC News, [Accessed: October 30, 2020].
4. KOERI (2020), -the October 30, 2020 Aegean Sea Earthquake press release (In Turkish)- Kandilli Observatory and Earthquake Research Institute, Bogazici University, Istanbul, Turkey. Available online: http://www.koeri.boun.edu.tr/, [Accessed: October 30, 2020].
5. USGS (2020), United States Geological Service, -the October 30, 2020 Earthquake Interactive Map-, Available online: https://earthquake.usgs.gov/, [Accessed: October 30, 2020].
6. AFAD (2020b), the Strong Ground Motion Database of Turkey, Disaster and Emergency Management of Turkey, Ankara, Turkey. Available online: https://tadas.afad.gov.tr/, [Accessed: October 30, 2020].
7. TEC (2007), Turkish Earthquake Code, Specification for Buildings to be Built in Seismic Zones, Ministry of Construction and Settlement, Ankara, Turkey.
8. TEC (2018), Turkish Earthquake Code, Turkish Building Earthquake Code, Republic of Turkey Ministry of Environment and Urbanisation, Ankara, Turkey.

9. Uhrhammer R (1986), “Characteristics of Northern and Southern California Seismicity”, Earthquake Notes, 57(1):21-41.
10. Deniz A., Yüksel E., Çelik C. O., Çakır Z., Yaltırak C., Serter E., Yıldırım H., Güllü A. (2020), 30.10.2020 İzmir Earthquake Assessment Report (In Turkish), Istanbul Technical University, Istanbul, Turkey.
11. TEC (1975), Turkish Earthquake Code, Regulation on Structures to be Built in Disaster Areas, Ministry of Public Works, Ankara, Turkey.
12. TEC (1998), Turkish Earthquake Code, Regulation on Structures to be Built in Disaster Areas, Ministry of Construction and Settlement, Ankara, Turkey.