Topographic signatures of kinematic segmentation and fault geometry along the Palu-Koro and Matano Faults, Indonesia

The Palu-Koro and Matano faults are among the fastest-slipping and most seismically active fault systems in eastern Indonesia, yet their kinematics and influence on landscape evolution remain debated. While topographic metrics are widely used to infer vertical displacement in extensional or compressional settings, their application in strike-slip systems, where deformation is predominantly horizontal, is less established. Here, we quantify topographic metrics including relief, channel steepness index (k_sn), mean slope (S), and hilltop curvature (C_HT) along both faults to characterise landscape response and identify interactions between fault segments. Using a quantile-based statistical approach, we classify topographic signals indicative of tectonic activity. Along the Matano fault, elevated metrics coincide with lithological contrasts and changes in fault geometry, whereas most of the fault exhibits subtle strike-slip-dominated topography. Along the Palu-Koro fault, segments of pure strike-slip motion show subdued metrics, while areas of complex geometry and transtension display elevated values. Subdued topographic segments also spatially correspond to zones of seismic quiescence. Preliminary InSAR observations suggest creeping behaviour in the western Matano fault and the aseismic portion of the Palu-Koro fault. These findings indicate that, although topographic metrics may not directly diagnose frictional slip modes, they effectively map kinematic segmentation and structural complexity that control vertical deformation in strike-slip systems. Integrating topographic metrics with geodetic data provides a powerful approach to identify and understand fault segmentation and interaction in complex strike-slip environments.