Geotechnical aspects of February 6, 2023 Kahramanmaraş- Türkiye earthquake sequence
Geotechnical aspects of February 6, 2023 Kahramanmaraş- Türkiye earthquake sequence
The earthquakes that occurred in Pazarcık and Ekinözü-Kahramanmaraş on February 6, 2023, had a profound impact southeastern Türkiye and northwestern Syria. With moment magnitudes of M7.8 and M7.6, these earthquakes, ruptured multiple fault segments within a span of 9 hours, presenting an unexpected scenario for seismic hazard assessments. During the Pazarcık event, the peak ground acceleration levels, corresponding to DD-1 (with a 2475-year return period) and DD-2 (with a 475-year return period) design levels as defined in the Turkish Building Earthquake Code, were exceeded at 5 and 22 strong ground motion stations, respectively. Ground motion prediction equations (GMPEs) underpredicted the recorded PGA levels at stations within 70 km from the fault rupture, particularly for the Pazarcık earthquake. Seismic soil liquefaction emerged as a significant geohazard, notably observed in Gölbaşı-Adıyaman and İskenderun-Hatay regions. The significant shaking triggered more than 3,000 landslides and rock falls, resulting in casualties. Damage to infrastructure was substantial, with 7 bridges sustaining significant damage, two of which were attributed to the liquefaction of foundation soils. Lifelines suffered significant damage due to fault rupture, liquefaction, and permanent ground deformations. Similarly, port facilities in İskenderun reported severe damage due to liquefaction and post-earthquake fires. Although all 140 dams in the influence region preserved their water retention capabilities, the reservoir levels at two of them had to be lowered as part of emergency response actions. While there was a partial collapse in a stone-paved railway tunnel serving the Gölbaşı- Malatya line, no major damage was reported at tunnel structures. Retaining structures, predominantly stone walls, incurred damages, whereas reinforced earth walls displayed greater resilience. The collapse or heavy damage to over 650,000 residential units was the major cause of over 55,000 casualties.