Although the Lajishan-Jishishan fault zone is considered as one of the most tectonically active orogenic belts along the northeastern margin of the Qinghai-Xizang Plateau, its present-day slip behavior and subsurface geometry remain poorly understood. The 2023 Jishishan earthquake, accompanied by high-resolution geodetic observations, offers a unique opportunity to advance our understanding of the regional tectonism. In this study, both Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) data are used to jointly constrain the coseismic slip distribution associated with the 2023 Jishishan earthquake. Our results suggest that rupture occurred along two distinct fault segments within the Jishishan fault zone: a primary northeast-dipping fault plane and a shallower southwest-dipping subsidiary fault. The inversion results of the double-fault model show a peak slip of 0.40 m on the main fault at a depth of 14.85 km and a peak slip of 0.09 m on the shallow subsidiary fault at 2.35 km depth. This double-fault rupture model is supported by multiple lines of evidence, including geodetic observations, seismological data, and surface fault mapping. The derived coseismic slip model sheds new light on the complex fault structure beneath the Jishi Shan, highlighting the possibility of segmented fault geometries and multi-fault interactions. Specifically, the northeast-dipping fault, identified as the Jishishan West Margin Fault Zone (JSSWF), appears to be intersected at depth by a southwest-dipping structure, likely corresponding to the Jishishan East Margin Fault Zone. This intersection may have disrupted rupture propagation, resulting in a discontinuity along the seismogenic fault plane. Notably, the 2023 rupture was confined to the lower portion of the seismogenic layer, leaving the upper segment of the JSSWF unruptured. This remaining strain accumulation in the shallow crust indicates a potentially persistent seismic hazard in the region.

The Southern Highland Fold and Thrust Belt (SHFTB), the boundary of the Australian plate and the New Guinea Highland block, significantly contributes to the convergent deformation along the plate boundary. However, due to the lack of observation data, the detailed slip pattern of the SHFTB and the orogenic mechanism beneath the New Guinea Highlands remains controversial. On 25 February 2018, the M_W7.5 Papua New Guinea (PNG) earthquake struck the southeastern segment of the SHFTB. The detailed rupture characteristics of this event is significant for further clarifying the inter-seismic slip pattern along the SHFTB. Here, the coseismic deformation field of this earthquake was obtained using high-resolution ALOS-2 satellite images. We find that the 2018 M_W7.5 PNG earthquake ruptured a large-scaled fault (SHFTB) extending to the lower crust (deeper than 20 km) beneath the New Guinea Highlands, with a dip angle of 24°. The slips on the fault plane are equivalent to moment magnitudes of M_W7.51. Three major asperities with thrust-dominated slip of up to 3.94 m are detected on the fault plane. This finding implies that the slip pattern on the eastern segment of the SHFTB is dominated by thrust, rather than with significant sinistral movement, as previously reported. The tectonic deformation across the New Guinea Highlands is possibly concentrated on the large-scale fault SHFTB and primarily controls the intra-continental orogeny in the central Papua New Guinea.