Multi‐Faceted Investigations of Crustal Deformation and Ionospheric Perturbations Associated With the 6 February 2023 Kahramanmaraş Earthquake Doublet in South‐Eastern Türkiye

Abstract The 6 February 2023 Kahramanmaraş Earthquake Doublet (Mw 7.8 and Mw 7.7) involved complex rupture patterns across multiple strands of the East Anatolian Fault (EAF) and Sürgü‐Çardak Fault (SCF) in SE Türkiye. The Mw 7.8 earthquake, triggered on a secondary fault, caused the rupture to propagate along the EAF for a distance of ∼300 km mainly towards north‐east direction. The subsequent Mw 7.7 earthquake ruptured an ∼150 km segment of the SCF with a prominent bilateral propagation from the hypocenter. Joint inversion of co‐seismic deformation fields derived from GPS and SAR observations reveals consistent left‐lateral strike‐slip motions for both the Mw 7.8 and Mw 7.7 events with peak slip amplitudes of ∼9.5 m and ∼11 m, respectively. GPS‐TEC estimates show co‐seismic ionospheric perturbations (CIP) with substantially larger amplitudes (∼1 TECU vs. 0.17 TECU) during the Mw 7.7 event, despite its lower magnitude. The compact high‐slip rupture and greater surface displacements (up to 4.41 m horizontal, 0.47 m subsidence) of the Mw 7.7 event represent the decisive source‐side factors elevating CIP amplitudes, with secondary amplification from favorable geomagnetic coupling southward of the epicenter and higher background ionospheric ionization.