Near-field ground motion intensity parameters of the major February 06, 2023, Türkey Kahramanmaraş earthquake sequences

Türkey is located in a seismically active region where the Anatolia, Africa, and Arabia tectonic plates converge. The high seismic hazard causes the region to be repeatedly struck by major earthquakes. On February 06, 2023, a devastating Mw 7.7 earthquake struck Türkey at 04:17 a.m. local time (01:17 UTC). Around 9 ​h later at 10:24 a.m. local time, another destructive Mw 7.6 earthquake struck at a distance of 95 ​km towards the north of the first earthquake (www.tadas.afad.gov.tr). The strong ground motion from the Mw 7.7 event shows peak ground accelerations exceeding 1 ​g in the near-field region and affected 11 cities. The effect of the complex fault geometry on the observed high PGAs needs to be examined to understand the associated structural damage. The present study investigates the key characteristics of strong ground motions recorded from 40 stations located in the vicinity of 100 ​km which are commonly used intensity parameters for vulnerability and risk analysis. The complex interaction between fault segments significantly influenced the overall rupture process and the distribution of ground shaking and generated significant pulse-like ground motions in the near-fault region. These ground motions exhibited directivity effects, characterized by pulse-like velocities, high peak ground accelerations, and spectral accelerations. The response spectra are derived for ground motions from several stations for the present destructive/major earthquake and are observed to exceed code prescribed spectra corresponding to the 475-year and 2475-year return periods.