Analysis of the First Year of Postseismic Movements Following the 2023 Kahramanmaraş (Türkiye) Earthquake Sequence Using InSAR Measurements

The 6 February 2023 sequence that was initiated by the failure of the <40 km-long Narlı fault turned out to be the biggest seismic event to occur in and around Türkiye during the modern times. While reaching a total rupture length of almost 450 km, the two separate sinistral events of Mw 7.7 and Mw 7.6 that took place 9 hours apart on the very same day also gave rise to an extremely heavy aftermath: loss of >50.000 lives and > USD 100 billion in economic damages.

We have analysed the first 12 months of postseismic movements following the February 2023 sequence using both Sentinel-1 and ALOS2 radar imagery. Movement along both the East Anatolian and Çardak fault zones are evident with the latter being more pronounced owing (probably) to the line-of-sight N-S insensitivity of the satellites. The time series analysis also shows movement along the westernmost part of the Sürgü fault and a ~20 km N-S oriented fault towards the western end of the Çardak rupture. The continuation of the dominantly E-W oriented Çardak rupture to northeast towards the city of Malatya is also evident in the postseismic data emphasizing once again the elevated seismic risk posed on the city.

Apart from the postseismic activity associated with the 2023 sequence another prominent feature observable in the radar data is the continuing aseismic movement along the Pütürge segment of the East Anatolian Fault Zone which was reported earlier by Çakır et al. (2023). Taking into account moderate earthquakes like the August 4^th, 2020 Mw 5.6 earthquake that took place in between the 2020 Mw 6.8 Sivrice-Elazığ earthquake rupture zone and the Yarpuzlu restraining bend where the Mw 7.7 event of the 2023 sequence has terminated; we propose that at least 20 km of the segment could still be unbroken.