Laterally heterogeneous rheological structure from postseismic deformation of the 2023 Kahramanmaraş earthquake sequence

This is the authors' abstract. We don't add key points for this paper.

Following the strongest recorded seismic event along the East Anatolian Fault Zone (EAFZ), the postseismic deformation of the 2023 Kahramanmaraş earthquake sequence offers a rare opportunity to probe the regional rheological structure. We develop a GNSS-prior constrained, logarithmic-decay based InSAR method (Plog-InSAR) to combine one year of postseismic geodetic data. We show that horizontal deformation is predominant with cumulative displacements up to 13 cm and vertical displacements exhibit a characteristic four-quadrant pattern. We find a combined model of coseismic-stress driven viscoelastic relaxation and afterslip outperforms any single-mechanism model in reproducing the observed postseismic deformation. Viscoelastic relaxation accounts for most of the mid- to far-field signal, whereas afterslip contributes predominantly to the near-field response. Our findings provide new constraints on laterally heterogeneous lithospheric rheology across the southern EAFZ and its role in partitioning postseismic deformation following the 2023 Kahramanmaraş earthquake sequence.