Fault geometry and rupture speed as controls on off-fault deformation in the 2023 Turkey-Syria earthquakes

Abstract

Coseismic off-fault deformation (OFD) measurements provide crucial insight into fault deformation behavior and shallow faulting damage. Although kinematic and dynamic characteristics of the causative faults associated with the 2023 Turkey-Syria earthquake doublet (Mw 7.8 and 7.6) were well determined, the OFD behavior and mechanism remain poorly constrained. Here we utilized high-resolution optical satellite geodesy to illuminate OFD distribution of the earthquake doublet. We found an average of ~80% and ~83% of coseismic fault deformation were localized on the primary fault planes of the Mw 7.8 and Mw 7.6 earthquakes, respectively; together, the remaining deformation manifested as OFD distributed within an average of 200-m- and 140-m-wide damage zones. Our observations revealed the OFD systematically increases in fault segments that have more complex geometry and slower coseismic rupture velocity, validating that both factors exhibit a significant facilitation on first-order variation of OFD during the earthquake doublet. Optical satellite observations of the 2023 Kahramanmaras earthquake doublet along the East Anatolian Fault Zone reveal that fault geometry complexity and rupture speed significantly influence off-fault damage

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