An Mw 7.8 Earthquake on 6 February 2023 on the East Anatolian Fault, Turkey

An earthquake of M w 7.8 occurred on 6 February 2023 at a depth of 18 km on the NE-SW trending East Anatolian Fault (EAF) in southern Turkey bordering Syria. This is the first time that an earthquake of M w ≥7.0 has occurred on EAF since 1900. The region lies on the triple-junction between the Arabian, African and Anatolian plates. The epicenter was located 32 km WNW of the Gaziantep city close to the Kahramanmaras Triple Junction (KMTJ) where the NNE-SSW Dead Sea transform fault (DSF) intersects the EAF. Based on the distribution of immediate aftershocks of 4.0≤M w ≤6.7 it is inferred that the fault rupture was bidirectional and broke a ∼300 km fault length of EAF in three segments of Amanos, Pazarcik and Erkenek. This earthquake triggered an event of M w 7.5 on the E-W Surgu Fault, ∼100 km north of the mainshock. Eleven cities suffered the worst damage where several multistoried structures collapsed killing more than 43,000 people. While the structures in the epicentral region collapsed due to very strong shaking induced by these two shallow and large earthquakes the collapse of structures in cities as far as 300 km suggests strong role of seismic wave amplification due to local site effects in addition to poor construction practices and non-compliance of seismic codes. The rupture of a ∼300 km fault length in three segments of EAF and its influence to trigger future large earthquakes in the adjacent four segments of Puturge, Palu, Ilica and Karliova in eastern Turkey by stress transfer in a cascading manner is discussed.