Characteristics of strong ground motion from the 2023 Mw 7.8 and Mw 7.6 Kahramanmaraş earthquake sequence

On the 6th February 2023 Mw 7.8 and Mw 7.6 Kahramanmaraş Earthquake Sequence occurred at the East Anatolian Fault Zone (EAFZ) and the Sürgü-Çardak Fault Zone (SCFZ), causing significant damage to buildings and infrastructure in southeast-central Türkiye and northern Syria, and claiming the lives of > 50,000 of people. We use the strong ground motion records provided by the Disaster and Emergency Management Presidency of Türkiye (AFAD) to discuss the characteristics of response spectra of interested stations, to identify and analyze the pulse-like ground motion records in the earthquake doublet, and compare the PGA, PGV, spectral acceleration and significant duration with the relevant prediction models. It is found that pulse-like ground motions are mainly distributed on the fault zone, and the velocity pulses are characterized by short-duration, short-period, and high-amplitude. The smaller pulse period may be due to the small proportion of low-frequency content energy of pulse-like ground motions. The residuals of the empirical model increase with the increase of V_S30, implying that the regional duration model needs to be further studied. The existing models significantly overestimates the significant duration of pulse-like ground motion records, which may be related to the directional effect of pulse-like ground motion. The existing model has well predicted the attenuation of ground motion for short periods, while the ground motion records in Türkiye attenuated faster for the larger distances (> 120 km). Due to the presence of many large-amplitude, long-period velocity pulse-like records in the near-fault, PGV and long-period response spectra of pulse-like ground motion records are underestimated by the existing model. The complex dynamics of the 2023 sequence justify further studies.