Satellite image-based structural mapping reveals new earthquake sources in eastern Indonesia: implications for active tectonics and earthquake hazards

Abstract The origin of large-scale tectonic extension in eastern Indonesia remains unresolved, as existing models do not account for the magnitude, spatial continuity, and kinematics of the observed deformation. Here we map active tectonic structures using 8-m-resolution Digital Elevation Model Nasional of Indonesia (DEMNAS) data and integrate these observations with geological constraints, GPS velocities, seismicity, and centroid moment tensor solutions. We show that extension is regionally pervasive, extending from the Banda Sea into the Lombok–Seram fold–thrust belt, the Aru Trough, and the Bird’s Neck region of New Guinea. This deformation is organised into a coherent network of normal and strike-slip fault zones. The Aru Trough is identified as an actively developing pull-apart basin linked to a major strike-slip system, while NE–SW-striking horsts and grabens in the Bird’s Neck demonstrate that extension involves the lower (Australian) plate. Kinematic indicators indicate NW–SE-directed extension driven by oblique plate convergence, producing transtension across Sulawesi, Seram–Buru, and the Aru Trough. In contrast, the Timor–Seram–Tanimbar frontal system is comparatively aseismic but retains significant seismic hazard potential. These results show that eastern Indonesia is best described as a wrench-dominated, obliquely convergent plate boundary with distributed transtension, rather than a system governed by simple slab rollback, with implications for understanding extension in highly curved convergent margins globally.