EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Estimation Of High-Frequency Attenuation Parameter (Kappa) For Hard Rock Stations Of Turkish Strong Motion Network

Atınç Özgün Akgün1, Zeynep Gülerce2, and Atilla Arda Özacar3
Atınç Özgün Akgün et al.
  • 1Middle East Technical University, Civil Engineering, Turkey (
  • 2Middle East Technical University, Civil Engineering, Turkey (
  • 3Middle East Technical University, Geological Engineering, Turkey (

Site-specific decay in the Fourier Amplitude Spectrum (FAS) at high frequencies, a.k.a. the zero-distance kappa (κ0), is frequently used in seismic analysis of critical infrastructure; especially for the host-to-target adjustment of the design spectrum and the site response analysis. The zero-distance kappa value for hard rock sites is more crucial but harder to constrain because the amount of strong-motion stations on hard-rock sites is limited in the global datasets. The objective of this study is to calculate the zero-distance kappa value for the hard rock strong-motion stations operated by the Disaster and Emergency Presidency of Turkey (AFAD). For this purpose, 6463 recordings from 22 strong-motion stations with measured average shear wave velocities at the first 30 meters (VS30) higher than 740m/s and having at least 100 records have been analyzed. The slope of the decay in the S-wave portion of the FAS (kappa) at high frequencies is determined for a carefully selected and record-specific frequency range. Variation of the kappa with epicentral distance is evaluated to determine the median zero-distance kappa and its uncertainty for each recording station. Estimated median zero-distance kappa values vary between 0.01s to 0.06s and are consistent with the limited amount of previously published data. Only a weak reduction in median zero-distance kappa is observed with increasing VS30 and a rather large scatter in kappa for the same VS30 values is observed. More robust results might be attained by isolating the site amplification effects of weak surficial layers and subcategorization based on available geological and geographical information.

How to cite: Akgün, A. Ö., Gülerce, Z., and Özacar, A. A.: Estimation Of High-Frequency Attenuation Parameter (Kappa) For Hard Rock Stations Of Turkish Strong Motion Network, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14253,, 2021.

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