Imaging the Northeastern End of the Mw7.7 Ekinozu Earthquake Rupture along the Çardak-Surgu Fault during the 2023 Kahramanmaraş, Türkiye, Earthquake Doublet

The Mw 7.7 Ekinozu Earthquake is the second shock of the devastating 2023 Kahramanmaraş earthquake doublet. It ruptured bilaterally along a ~150 km-long stretch of the Cardak-Surgu fault. Along its eastern section, instead of propagating along the Surgu fault to connect with the main East Anatolian Fault where the Mw7.8 shock occurred, the rupture unexpectedly turned to the northeast to propagate along a secondary structure. Surface ruptures and assessment of displacement along that section of the fault have been challenging to map, and these are less documented. This is crucial for unraveling the entire rupture process, fault growth, and related seismic hazards. In this study, we focus on the eastern end of the ~57-km long surface rupture caused by the Mw 7.7 Ekinozu Earthquake. By correlating high-resolution optical images SPOT (pre-earthquakes, resolution 1.5m) and Pléiades (post-earthquakes, resolution 50 cm), we computed displacement maps at 1.5 m ground resolution for the study area. In addition, using the post-event Pleiades images, we meticulously characterized the coseismic surface ruptures in detail. Our mapping presents a segmented surface rupture trace with azimuth variations and several distinguishably complex geometries, such as double bends and branches. Furthermore, our investigation includes precise measurements of on- and off-fault surface displacement with sub-pixel detection over the ~57-km long section. Our findings underscore the significance of detailed interpretations of coseismic surface rupture and coseismic displacement measurements in comprehending the propagation of the seismic rupture.