Estimation of S-wave velocity structure and site response characteristics by microtremor array explorations in the Bornova Basin (İzmir, Türkiye)
Engineering Geology, cilt.373, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 373
- Basım Tarihi: 2026
- Doi Numarası: 10.1016/j.enggeo.2026.109038
- Dergi Adı: Engineering Geology
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Compendex, Geobase, INSPEC, Academic Search Ultimate (EBSCO), Engineering Source (EBSCO)
- Anahtar Kelimeler: 30 October 2020 Samos earthquake, Bornova basin, Damage, Microtremor array exploration, Phase velocity, Shear-wave velocity, Site amplification, Vs30, İzmir
- Dokuz Eylül Üniversitesi Adresli: Evet
Özet
This study aimed to explore the S-wave velocity structure of soils using microtremor array explorations to define the deep geological geometry of the Bornova Basin (İzmir, Türkiye), where destruction was observed during the 30 October 2020 Samos earthquake (Mw 7.0). At least 30-60 minutes of microtremor records were collected using circular-array measurements at three different radii at 34 sites in the Bornova Basin to determine the variation of 1D S-wave velocity with target depth down to ∼300-500 m. This methodological approach allows us to define the sediment layers situated between the surface and the boundaries of the Neogene rock layers within the basin. The phase velocities of Rayleigh waves were estimated by using a Spatial Autocorrelation method. Subsequently, the Geopsy software and the hybrid genetic simulated annealing algorithm were used to obtain a 1D S-wave velocity structure at each site. A comparison was made between the horizontal-to-vertical spectral ratio of microtremors and the computed ellipticities of the fundamental mode Rayleigh waves. This comparison showed good agreement with velocity models. The depth of the engineering bedrock varies from ∼60 m to 200 m along the coastline with a velocity range of 700-1200 m/s, and it ranges between ∼20 and 225 m in the Bornova Basin. The linear soil amplifications observed at the sites are calculated using the 1D Vs models obtained from the inversions. The reasons for the intensive damage in a part of the basin are attributable not only to the low Vs soil structure and site amplification, but also to the building construction and material features. The results indicate that the low fundamental frequency range (0.6-0.8 Hz) of the soil structure and the natural frequencies of the high-rise buildings might coincide, and resonance phenomena might occur during the 2020 Samos earthquake (Mw 7.0).