Identification of Source Faults of Large Earthquakes in the Turkey-Syria
Border Region Between AD 1000 and Present, and their Relevance for the
2023 Mw 7.8 Pazarcık Earthquake
Abstract
The February 6th, 2023, Mw 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 (Mmax) of earthquakes on the East Anatolian fault 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 Mw ≥ 7 earthquakes between AD 1000 and
the present in the region. We find that the 2023 Pazarcık earthquake
could have been foreseen in terms of location (the East Anatolian Fault)
and timing (an earthquake along this fault was if anything overdue), but
not magnitude. We hypothesize that the maximum earthquake magnitude for
the East Anatolian Fault is in fact 8.2, i.e. a single end-to-end
rupture of the entire fault, and that the 2023 Pazarcık earthquake did
not reach Mmax by chance only. In fact, we suggest that such unusually
large events are hard to model in terms of recurrence intervals, because
they need a very specific set of circumstances to line up before they
can happen. We also conclude 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.