Evaluating Seismic Site Response in a Deep Alluvial Basin: The Case of the Bornova Basin (Izmir)

Abstract

This research investigates the effects of deep alluvial basins in the Bornova region of Izmir on earthquake ground motion by combining field characterization with 1D and 2D equivalent linear soil response analyzes. In the study, soil-bedrock interfaces were modeled using two idealized two-dimensional geological sections representing the Bornova Basin. The study area has a geological environment characterized by east-west trending normal faults along the Inner Izmir Bay and covered by sedimentary units. Borehole data indicate the presence of heterogeneous geological units consisting of clay, silt, sand, and gravel in some areas. The Spatial Autocorrelation (SPAC) method indicates that, in the west, the alluvial units with low shear-wave velocities become thicker with depth, whereas in the east, shear-wave velocities increase from the surface downward. In the analysis, the shear modulus reduction and damping-ratio curves obtained from laboratory experiments were compared with widely used reference curves in the literature, and the most suitable curves were used in the analysis. The analysis used three different recordings: the 1999 Duzce earthquake record, the 30 October 2020 Samos earthquake record, and a superposition of Gabor pulse compatible with the target spectrum. The 2D analysis shows higher spectral acceleration values compared to the 1D analyses, and hip enlargement is concentrated in the ~0.3, 1.0, and 1.6 s period range. This situation aligns with the damage distribution observed during the 2020 Samos earthquake (Mw 6.6), indicating that basin effects in Bornova were decisive during the earthquake.

Keywords

• Bornova Basin
• Site Response
• Basin Effects
• Dynamic Analysis

Derin Alüvyon Bir Basende Sismik Zemin Tepkisinin Tepkisi: Bornova Baseni (İzmir) Örneği

Öz

Bu araştırma, İzmir Bornova bölgesindeki derin alüvyon basenlerinin deprem yer hareketi üzerindeki etkilerini, saha karakterizasyonu ile 1B ve 2B eşdeğer lineer zemin tepki analizlerini birleştirilerek araştırmaktadır. Çalışmada, Bornova Basenini temsil eden iki adet idealize edilmiş iki boyutlu jeolojik kesit kullanılarak zemin–kaya ara yüzeyleri modellenmiştir. Çalışma alanı, İç İzmir Körfezi boyunca uzanan doğu-batı yönlü normal faylarla sınırlanan ve sedimanter birimlerle kaplı bir jeolojik yapıya sahiptir. Sondaj verileri, bazı bölgelerde kil, silt, kum ve yer yer çakılların olduğu heterojen jeolojik birimlerin olduğunu göstermektedir. Uzaysal Otokorelasyon (SPAC) yöntemi ise batıda düşük kayma dalgası hızına sahip alüvyon birimlerin derinleştiğini, doğuda ise kayma dalgası hızlarının yüzeyden derine doğru arttığını göstermektedir. Analizlerde, laboratuvar deneylerinden elde edilen kayma modülü azalım ve sönüm oranı eğrileri literatürde yaygın olarak kullanılan referans eğrilerle karşılaştırılarak en uygun eğriler analizlerde kullanılmıştır. Analizlerde, 1999 Düzce depremi kaydı, 30 Ekim 2020 Samos depremi kaydı ve hedef spektruma uyumlu Gabor dalgacıklarının süperpozisyonu ile oluşturulmuş üç farklı kayıt kullanılmıştır2B analizler, 1B analizlere kıyasla daha yüksek spektral ivme değerleri göstermiş; büyütme ise yaklaşık 0.3, 1.0 ve 1.6 s periyot aralıklarında yoğunlaşmıştır. Bu durum, 2020 Samos depremindeki (Mw 6.6) hasar dağılımıyla örtüşmekte ve Bornova’daki basen etkilerinin deprem sırasında belirleyici olduğunu göstermektedir.

Anahtar Kelimeler

• Bornova Baseni
• Saha Tepkisi
• Basen Etkileri
• Dinamik Analiz

Kaynakça

1. [1] Ayoubi, P., Mohammadi, K., Asimaki, D., “A systematic analysis of basin effects on surface ground motion”, Soil Dynamics and Earthquake Engineering, 141: 106490, (2021).
2. [2] Isık, N.S., “Basin and Near-Fault Effects on Earthquake Ground Motions: An Evaluation of the Antakya Records of the Kahramanmaras Pazarcık Earthquake”, Journal of Geological Engineering, 47: 67–86, (2023). DOI: 10.24232/jmd.1299007
3. [3] Pitilakis, K., “Site Effects”, in: Ansal, A. (Ed.), Recent Advances in Earthquake Geotechnical Engineering and Microzonation, Geotechnical, Geological, and Earthquake Engineering, Vol. 1, Springer, Dordrecht, 139–197, (2004).
4. [4] Safak, E., “Local site effects and dynamic soil behavior”, Soil Dynamics and Earthquake Engineering, 21: 453–458, (2001).
5. [5] Pelekis, P., Batilas, A., Pefani, E., Vlachakis, V., Athanasopoulos, G., “Surface topography and site stratigraphy effects on the seismic response of a slope in the Achaia–Ilia (Greece) 2008 Mw6.4 earthquake”, Soil Dynamics and Earthquake Engineering, 100: 538–554, (2017).
6. [6] Mayoral, J.M., Asimaki, D., Tepalcapa, S., Wood, C., Roman-de la Sancha, A., Hutchinson, T., Franke, K., Montalva, G., “Site effects in Mexico City basin: Past and present”, Soil Dynamics and Earthquake Engineering, 121: 369–382, (2019).
7. [7] Boore, D.M., “Can site response be predicted?”, Journal of Earthquake Engineering, 8: 1–41, (2004). DOI: https://doi.org/10.1142/S1363246904001651
8. [8] Thompson, E.M., Baise, L.G., Kayen, R.E., Guzina, B.B., “Impediments to predicting site response: Seismic property estimation and modeling simplifications”, Bulletin of the Seismological Society of America, 99: 2927–2949, (2009).

9. [9] Hanks, T.C., “Strong ground motion of the San Fernando, California, earthquake: Ground displacements”, Bulletin of the Seismological Society of America, 65: 193–225, (1975).
10. [10] Kawase, H., Aki, K., “A study of the response of a soft basin for incident S, P, and Rayleigh waves with special reference to the long duration observed in Mexico City”, Bulletin of the Seismological Society of America, 79: 1361–1382, (1989).
11. [11] Bard, P.Y., Campillo, M., Chavez-Garcia, F.J., Sanchez-Sesma, F., “The Mexico earthquake of September 19, 1985 – A theoretical investigation of large- and small-scale amplification effects in the Mexico City valley”, Earthquake Spectra, 4: 609–633, (1988).
12. [12] Semblat, J.F., Pecker, A., Waves and Vibrations in Soils: Earthquakes, Traffic, Shocks, Construction Works, IUSS Press, Pavia, (2009). ISBN: 978-88-6198-030-3
13. [13] Bakir, B.S., Ozkan, M.Y., Ciliz, S., “Effects of basin edge on the distribution of damage in the 1995 Dinar, Türkiye earthquake”, Soil Dynamics and Earthquake Engineering, (2002).
14. [14] Khanbabazadeh, H., Hasal, M.E., Iyisan, R., “2D seismic response of the Duzce Basin, Turkey”, Soil Dynamics and Earthquake Engineering, 125: 105754, (2019).
15. [15] Kamiyama, M., Satoh, T., “Seismic response analysis of laterally inhomogeneous ground with emphasis on strains”, Soil Dynamics and Earthquake Engineering, 22: 877–884, (2002).
16. [16] Makra, K., Chavez-Garcia, F.J., Raptakis, D., Pitilakis, K., “Parametric analysis of the seismic response of a 2D sedimentary valley: Implications for code implementations of complex site effects”, Soil Dynamics and Earthquake Engineering, 25: 303–315, (2005).
17. [17] Makra, K., Chavez-Garcia, F.J., “Site effects in 3D basins using 1D and 2D models: An evaluation of the differences based on simulations of the seismic response of Euroseistest”, Bulletin of Earthquake Engineering, 14: 1177–1194, (2016).
18. [18] Yniesta, S., Brandenberg, S.J., Shafiee, A., “ARCS: A one-dimensional nonlinear soil model for ground response analysis”, Soil Dynamics and Earthquake Engineering, (2017).
19. [19] Semblat, J.F., Dangla, P., Kham, M., Duval, A.M., “Seismic site effects for shallow and deep alluvial basins: In-depth motion and focusing effect”, Soil Dynamics and Earthquake Engineering, 22: 849–854, (2002).
20. [20] Narayan, J.P., Kumar, R., “Spatial spectral amplification of basin-transduced Rayleigh waves”, Natural Hazards, 71: 751–765, (2014).
21. [21] Khanbabazadeh, H., Iyisan, R., Ansal, A., Hasal, M.E., “2D non-linear seismic response of the Dinar basin, Turkey”, Soil Dynamics and Earthquake Engineering, 89: 5–11, (2016).
22. [22] Zhu, C., Chavez-Garcia, F.J., Thambiratnam, D., Gallage, C., “Quantifying the edge-induced seismic aggravation in shallow basins relative to the 1D SH modelling”, Soil Dynamics and Earthquake Engineering, 115: 402–412, (2018).
23. [23] Hasal, M.E., Iyisan, R., “Effect of edge slope on soil amplification at a two-dimensional basin model”, Proceedings of the 15th World Conference on Earthquake Engineering (Paper No. 4455), Lisbon, Portugal, (2012).
24. [24] Iyisan, R., Khanbabazadeh, H., “A numerical study on the basin edge effect on soil amplification”, Bulletin of Earthquake Engineering, 11: 1305–1323, (2013).
25. [25] Madiai, C., Facciorusso, J., Gargini, E., Baglione, M., “1D versus 2D site effects from numerical analyses on a cross section at Barberino di Mugello (Tuscany, Italy)”, Procedia Engineering, 158: 499–504, (2016). DOI: https://doi.org/10.1016/j.proeng.2016.08.479
26. [26] Abraham, J.R., Lai, C.G., Papageorgiou, A., “Basin-effects observed during the 2012 Emilia earthquake sequence in Northern Italy”, Soil Dynamics and Earthquake Engineering, 78: 230–242, (2015).
27. [27] Kramer, S.L., Stewart, J.P., Geotechnical Earthquake Engineering, 2nd ed., CRC Press, Boca Raton, (2025). DOI: 10.1201/9781003512011, ISBN: 9781003512011
28. [28] AFAD, “Preliminary evaluation report for the Mw=6.6 October 30, 2020, Earthquake off the coast (17.26 km) of Seferihisar-Aegean Sea (Izmir)”, Republic of Turkey Ministry of Interior Disaster and Emergency Management Authority (AFAD), Ankara, (2020).
29. [29] Cetin, K.O., Zarzour, M., Cakır, E., Tuna, S.C., Altun, S., “2-D and 3-D basin site effects in Izmir-Bayrakli during the October 30, 2020, Mw7.0 Samos earthquake”, Bulletin of Earthquake Engineering, 21: 5419–5442, (2023).
30. [30] Pamuk, E., Ozdağ, O.C., Akgün, M., “Soil characterization of Bornova Plain (Izmir, Turkey) and its surroundings using a combined survey of MASW and ReMi methods and Nakamura’s (HVSR) technique”, Bulletin of Engineering Geology and the Environment, 78: 2459–2474, (2019). DOI: https://doi.org/10.1007/s10064-018-1293-7
31. [31] Pamuk, E., “Investigation of soil dynamic characteristics and modeling soil–bedrock interfaces of Bornova Plain and its surroundings (Eastern Izmir Bay/Western Turkey)”, Ph.D. Thesis, Dokuz Eylül University, Graduate School of Natural and Applied Sciences, Department of Geophysical Engineering, Izmir, (2018).
32. [32] Uzel, B., Sozbilir, H., Ozkaymak, Ç., “Neotectonic evolution of an actively growing superimposed basin in western Anatolia: The Inner Bay of Izmir, Turkey”, Turkish Journal of Earth Sciences, 21(4): 539–566, (2012). https://doi.org/10.3906/yer-0910-11
33. [33] Okay, A.I., Satır, M., Maluski, H., Siyako, M., Monie, P., Metzger, R., Akyuz, S., “Paleo- and Neo-Tethyan events in northwest Turkey: Geological and geochronological constraints”, in: Yin, A., Harrison, M. (Eds.), Tectonics of Asia, Cambridge University Press, Cambridge, pp. 420–441, (1996). ISBN: 9780521480492
34. [34] Kıncal, C., “İzmir İç Körfezi çevresinde yer alan birimlerin coğrafi bilgi sistemleri ve uzaktan algılama teknikleri kullanılarak mühendislik jeolojisi açısından değerlendirilmesi”, Ph.D. Thesis, Dokuz Eylül University, İzmir, (2004).
35. [35] Pamuk, E., Gönenç, T., Özdağ, Ö.C., Akış, M., “3D bedrock structure of Bornova Plain and its surroundings (Izmir/Western Turkey)”, Pure and Applied Geophysics, 175: 325–340, (2018). DOI: https://doi.org/10.1007/s00024-017-1681-0
36. [36] Aki, K., “Space and time spectra of stationary stochastic waves, with special reference to microtremors”, Bulletin of the Earthquake Research Institute, University of Tokyo, 35, 415–457, (1957).
37. [37] Henstridge, J.D., “A signal processing method for circular arrays”, Geophysics, 44(2), 179–184, (1979).
38. [38] Tsai, V.C. ve Moschetti, M.P., “An explicit relationship between time-domain noise correlation and spatial autocorrelation (SPAC) results”, Geophysical Journal International, 182(1), 454–460, (2010).
39. [39] Vucetic, M., Dobry, R., “Effects of soil plasticity on cyclic response”, Journal of Geotechnical Engineering, ASCE, 120(12): 1764–1787, (1991).
40. [40] Darendeli, M.B., “Development of a new family of normalized modulus reduction and material damping curves”, Ph.D. Thesis, The University of Texas at Austin, (2001).
41. [41] EPRI, “Guidelines for determining design basis ground motions”, Electric Power Research Institute, Report No. TR-102293, Palo Alto, California, (1993).
42. [42] Ministry of Interior, Disaster and Emergency Management Authority (AFAD), “Turkish Building Earthquake Code (TBEC-2018)”, Ankara, Turkey, (2018).
43. [43] Pacific Earthquake Engineering Research Center (PEER), “PEER Ground Motion Database”, University of California, Berkeley, USA. Available at: https://peer.berkeley.edu/peer-ground-motion-database (Accessed: 10.10.2025).
44. [44] AFAD, “Turkey Accelerometric Database and Analysis System (TADAS) – Turkish Seismic Hazard Map and Strong Motion Stations”, Disaster and Emergency Management Authority (AFAD), Department of Earthquake, Ankara, Turkey. Available at: https://tadas.afad.gov.tr/map (Accessed: 10.10.2025).
45. [45] Rodriguez-Plata, R., Ozcebe, A.G., Smerzini, C., Lai, C.G., “Aggravation factors for 2D site effects in sedimentary basins: The case of Norcia, central Italy”, Soil Dynamics and Earthquake Engineering, 149: 106854, (2021).
46. [46] Rocscience Inc., “RSSeismic User Guide: RSSeismic Overview”, Rocscience Software Documentation, (2025).
47. [47] Mangifesta, M., “Visual-Q4M User’s Guide (Version 2.0): Pre & Post Processor for Evaluating the Seismic Response of Soil Structures”, (2025).
48. [48] Hudson, M., Idriss, I.M., Beikae, M., “QUAD4M – A computer program to evaluate the seismic response of soil structures using finite element procedures and incorporating a compliant base”, Center for Geotechnical Modeling, Department of Civil and Environmental Engineering, University of California, Davis, CA, (1994).