Comprehensive ground-motion characterization of the 6 February 2023 \(\:{\varvec{M}}_{\varvec{W}}\) 7.8 Pazarcık earthquake in Kahramanmaraş, Türkiye: insights into attenuation effects, site responses and source properties

Abstract

The devastating \(\:{M}_{W}\) 7.8 Pazarcık earthquake on February 6, 2023, profoundly impacted a large region in south-central Türkiye and northwestern Syria, resulting in over 50,000 casualties and widespread damage. To better understand source properties and wave-propagation effects of this event, we analyze the strong ground-motion data recorded at ~ 230 stations. We determine the regional distance-dependent attenuation using the horizontal RotD50 Fourier acceleration amplitude spectrum (FAS) in the frequency range of 0.1–20 Hz. We find an apparent near-source saturation effect which needs to incorporate an additional finite-fault factor for the distance scaling. Uncertainty and sensitivity analyses are considered by variable decay rates in the geometric spreading model. For each decay rate, we derive a corresponding \(\:Q\left(f\right)\) model to account for the frequency-dependent anelastic attention. Significant duration of ground motions is modelled for two different measurements based on Arias intensity (\(\:{I}_{A}\)). For site amplification, we construct a model containing both \(\:{V}_{S30}\)-scaling and peak ground acceleration (PGA)-scaling. Source parameters are then determined using a reference Fourier source spectrum at 1.0 km. Specifically, we estimate the mean corner-frequency as \(\:{f}_{0}\)= 0.036 Hz, Brune stress drop as Δσ = 4.79 MPa and the reference rock site κ₀ = 0.051 s. By analyzing near-source pulse-like waveforms, we demonstrate that the mismatch of peak ground velocity (PGV) between our model and close-distance observations is due to the rupture directivity effect. Finally, we compare ground motions of the 2023 \(\:{M}_{W}\) 7.8 event to those of the 2023 \(\:{M}_{W}\) 7.6 Elbistan and the 2020 \(\:{M}_{W}\) 6.7 Sivrice earthquakes. Attenuation effects estimated for the three events are found to be identical between ~ 0.2 and 6.0 Hz, with slight differences in site responses above ~ 5.0 Hz. Source spectra comparisons indicate that the source properties are complicated for all three events. Our comprehensive ground-motion analyses contribute to understanding and modeling regional properties of attenuation, site response, and event-based source characteristics that are important for future region-specific seismic hazard assessment.