Identification of Source Faults of Large Earthquakes in the Turkey‐Syria Border Region Between 1000 CE and the Present, and Their Relevance for the 2023 M w 7.8 Pazarcık Earthquake

The 6 February 2023, M w 7.8 Pazarcık earthquake in the Turkey‐Syria border region raises the question of whether such a large earthquake could have been foreseen, as well as what is the maximum possible magnitude ( M max ) of earthquakes on the East Anatolian Fault (EAF) system and on continental transform faults in general. To answer such questions, knowledge of past earthquakes and of their causative faults is necessary. Here, we integrate data from historical seismology, paleoseismology, archeoseismology, and remote sensing to identify the likely source faults of fourteen M w ≥ 7 earthquakes between 1000 CE and the present in the region. We find that the 2023 Pazarcık earthquake could have been foreseen in terms of location (the EAF) and timing (an earthquake along this fault was if anything overdue), but not magnitude. We hypothesize that the maximum earthquake magnitude for the EAF is in fact 8.2, that is, a single end‐to‐end rupture of the entire fault, and that the 2023 Pazarcık earthquake did not reach M max by a fortuitous combination of circumstances. We conclude that such unusually large events are hard to model in terms of recurrence intervals, and that seismic hazard assessment along continental transforms cannot be done on individual fault systems but must include neighboring systems as well, because they are not kinematically independent at any time scale. On 6 February 2023, there was a magnitude 7.8 earthquake in the Turkey‐Syria border region. It surprised many people, including many Earth scientists, because of where it happened (on the East Anatolian fault [EAF]) and because of how large it was. People wondered whether it could have been foreseen, and how large an earthquake on this fault can really be. To figure this out, we looked at the history of earthquakes in the region in the last 1,000 years. We used information from historical seismology, paleoseismology, archeoseismology, and remote sensing to identify the faults that caused 14 earthquakes with magnitude 7 or greater in this region. We found that the location (EAF) and timing (it was due any time) of the 2023 earthquake were foreseeable, but not the magnitude. In fact, we believe that the maximum magnitude for the EAF is 8.2, and that the 2023 earthquake was below this maximum just by accident. It is hard to say how often such large events can happen, because many different things need to align. We also believe that it is necessary to look at neighboring fault systems when e