3D Physics-Based Simulation of Basin Amplification in the February 6, 2023 Kahramanmaraş Earthquakes

Bilgen B., Askan Gündoğan A.

SSA 2026 Annual Meeting, California, Amerika Birleşik Devletleri, 14 - 18 Nisan 2026, cilt.97, sa.2, ss.1365, (Özet Bildiri)

  • Yayın Türü: Bildiri / Özet Bildiri
  • Cilt numarası: 97
  • Doi Numarası: 10.1785/0220260133
  • Basıldığı Şehir: California
  • Basıldığı Ülke: Amerika Birleşik Devletleri
  • Sayfa Sayıları: ss.1365
  • Orta Doğu Teknik Üniversitesi Adresli: Evet

Özet

Sedimentary basins can significantly amplify ground motions during earthquakes, making basin effects a critical topic in earthquake engineering. Within basins, incident S waves often convert into surface waves, causing wave trapping and prolonged shaking. Because amplification depends on factors such as low-velocity sediments, strong impedance contrasts, and complex three-dimensional basin geometry, 3-D physics-based simulations are essential for quantifying these effects. In this study, we use SPECFEM3D, an open-source spectral-element code for 3-D seismic wave propagation, to investigate basin amplification during the February 6, 2023 Kahramanmaraş earthquakes (Mw 7.8 Pazarcık and Mw 7.5 Elbistan). Source characterization is improved using a finite-fault model derived from wavelet inversion to introduce rupture directivity and reduce misfits associated with single-point sources.

Basin response is evaluated using two velocity models: (1) a low-resolution tomography from the IRIS EMC, and (2) a new 3-D velocity model constructed from a VS30 dependent 1-D velocity model that provides a high-resolution definition of the shallow VS structure. Simulated ground motions are validated against observed seismograms in the time and frequency domains using low-pass filtering and goodness-of-fit criteria. The high-resolution model is then used to compute basin amplification factors (BAFs) in Kahramanmaraş by comparing simulated time histories at identical isosurfaces, defined as the ratio between simulations with and without basin structure. To assess long-period basin effects, spectral accelerations from the simulations are used to quantify period-dependent amplification, allowing evaluation of how structural periods relevant to different building types may require adjustments to design values inside versus outside the basin. This work provides new constraints on basin amplification in the Kahramanmaraş region and highlights the importance of high-resolution velocity models for improving 3-D physics-based ground-motion simulations.