Increased motion of a slow-moving landslide following 2023 Kahramanmaraş Earthquake Doublet: Insights from Meydandere (Siirt) Landslide Complex, Türkiye

Slow-moving (5x10^-5 (mm/s)), deep-seated (>5 m) landslides exhibit persistent but non-uniform motion at low velocities, and deformation rates can increase abruptly with a triggering factor such as earthquakes.  Although it is generally reported that such landslides become reactive in areas close to earthquake epicenters depending on the attenuation relations, the Meydandere (Siirt) landslide is approximately 560 km away from the February 06, Kahramanmaraş earthquake epicenters, and due to the increased movement on the hillslopes a couple of days after the earthquake, local people reported the incident to the local authorities. Meydandere paleo landslide complex contains many secondary landslides and is developed in the Paleocene–Early Eocene sedimentary rocks. Here, we utilize four years of Interferometric Synthetic Aperture Radar, accumulated precipitation, and volumetric soil water layer data to explore a slow-moving landslide's kinematics and causal linkage with far-field seismic effects. Based on the InSAR results, we have determined that the deformation rate of different secondary landslide bodies in the main landslide complex is slow but continuous with time, yet this rate has doubled after the earthquakes. We have revealed that cumulative precipitation and volumetric soil water layer changes may also play a profound role in this rate. On the other hand, we have statistically shown that the February 6, 2023, earthquake doublet has a primary control on landslide acceleration because there is no significant increasing trend in the velocities, although the peak values of precipitation-induced changes were higher in the previous period. We conclude that understanding the earthquake response not only of co-seismic landslides in earthquake-affected areas but also of existing large bedrock landslides in far-field areas relative to the earthquake epicenter will provide a comprehensive understanding of the hazard chain of large earthquakes.