Crustal Deformation Pattern of Laji Shan-Jishi Shan Tectonic Belt from Integrated GNSS and InSAR Observations

Summary The Laji Shan-Jishi Shan Tectonic Belt (L-JTB), situated at a crucial tectonic transfer position on the northeastern margin of the Tibetan Plateau, is important for understanding regional deformation partitioning and seismic hazard. Although it has traditionally been regarded as a zone of relatively modest deformation, the 2023 Jishishan Mw 6.0 earthquake highlights the need to reassess its present-day kinematics and mechanical role. In this study, we integrate GNSS and Sentinel-1 InSAR data to derive a high-resolution three-dimensional interseismic crustal deformation field. We then apply an enhanced dip-aware velocity-profile model within a Bayesian framework to estimate the slip rates and locking characteristics of the major faults, and we further calculate the regional strain-rate field using a multiscale spherical wavelet approach. The results indicate that: (1) The L-JTB exhibits a modest average regional strain level relative to the first-order boundary faults to its north and south, but also displays pronounced along-strike heterogeneity and localized deformation focusing within the belt; (2) The Laji Shan Fault is characterized by a comparatively weak interseismic signal and is dominated by shortening and uplift, with only a minor fault-parallel component, whereas the Jishi Shan Fault is more strongly active, accommodating dextral strike-slip at 1.7 ± 0.3 mm/yr together with shortening-related dip-slip at 3.5 ± 1.2 mm/yr; and (3) the L-JTB is better interpreted as an internal strain transfer belt between the dextral Riyue Shan Fault and the sinistral West Qinling Fault, in which part of the transferred deformation is converted into crustal shortening, uplift, and localized internal strain. Our study reveals that even within a tectonic transfer belt characterized by only modest average regional strain, moderate earthquakes may still nucleate where deformation becomes localized through favorable stepover geometry, structural segmentation, and local strain focusing.