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Strong Ground Motion Characterization for the 6 February 2023 Mw 7.8 Pazarcık Earthquake in Kahramanmaraş, Türkiye

Description: 

The devastating 2023 Mw 7.8 Pazarcık earthquake, had a profound impact on south-central Türkiye and northwestern Syria, resulting in over 50,000 casualties and widespread damage. To better understand earthquake source properties and wave-propagation effects, we analyze strong ground-motion data recorded at ~230 stations. Our study involves determining regional distance-dependent attenuation using the Fourier acceleration amplitude spectrum (FAS) within the frequency 0.1 – 20 Hz. An apparent near-source saturation effect necessitates the incorporation of an additional finite-fault factor for distance scaling. We conduct uncertainty and sensitivity analyses, considering variable decay rates in the geometric spreading model. Significant duration of ground motions is modelled for two different measurements based on Arias intensity. We then construct a site amplification model incorporating both V_S30-scaling and peak ground acceleration (PGA)-scaling. Source parameters are then determined by fitting a theoretical Brune’s ω² model with a reference Fourier source spectrum at 1.0 km. Our estimates result in a mean corner-frequency 𝑓₀= 0.036 Hz, a Brune stress drop Δσ = 4.79 MPa, and a reference rock site (V_S30 = 800 m/s) κ₀ = 0.051 s. Analyzing near-source pulse-like waveforms, we demonstrate that the mismatch of peak ground velocity (PGV) between our model and near-fault observations is due to rupture directivity. Finally, we compare ground motions of the Mw 7.8 Pazarcık event to those of Mw 7.6 Elbistan and the 2020 Mw 6.7 Sivrice earthquakes. We find that the attenuation effects for the three events are identical in the frequency range ~0.2 – 6.0 Hz, with only minor differences in site responses above ~5.0 Hz. Source-spectra comparisons clearly indicate complex source properties for all three events. Our ground-motion analyses contribute to a better understanding and modeling of regional properties of attenuation, site response, and event-based source characteristics that are important for future region-specific seismic hazard assessment.

Session: Illuminating Complex, Multiplet Earthquake Sequences at Kahramanmaras (Turkiye), Herat (Afghanistan), and Beyond - II

Type: Oral

Date: 5/2/2024

Presentation Time: 10:45 AM (local time)

Presenting Author: Yuxiang

Student Presenter: No

Invited Presentation: 

Authors