Regional Strain Rates and Seismogenic Potential of the North Segment of the North–South Seismic Belt, China: Constraints from GNSS Observations

Based on GNSS observations from the Crustal Movement Observation Network of China (CMONOC) spanning 1998–2024, this study investigates crustal deformation characteristics within the northern segment of the North–South Seismic Belt in China. The analysis incorporates the horizontal velocity field, strain rate field, sub-block strain rates, fault slip rates, and associated slip deficits. The results reveal extensional deformation across five tectonic units: the eastern Qiangtang Block, the central–eastern Bayan Har Block, the central Qilian Block, the northern Alxa Block, and the north–central Longzhong Basin. Compressional deformation is predominantly localized along the northern and southern boundaries of the Qilian Block, the western margin of the southern Qaidam Block, the eastern segment of the East Kunlun Fault, and the Hoh Xil region. Zones of elevated shear strain rate are principally concentrated in four regions: the junction of the northern Qilian Block and the Alxa Block, the southern Qaidam Block, the central–eastern Bayan Har Block, and the eastern Qiangtang Block. Historical peak values of maximum principal extensional-shear strain are identified in the northern Longzhong Basin, whereas peak compressional-shear strain occurs in the central Qilian Block–western Qaidam Block and the eastern Qiangtang Block. The analysis reveals heterogeneous fault locking along the northern Western Qinling Range. Most segments of the East Kunlun Fault exhibit slip deficits, with the exception of the Alak Lake–Tusuo Lake segment. The degree of locking is generally homogeneous, except for the Tusuo Lake and Maqu segments. Both the slip deficit and slip rate of the Liupanshan Fault exhibit an increasing trend along its strike. Regions with high seismic hazard potential are identified, primarily including: the Xiugou–Maqiu segment of the East Kunlun Fault, the Guyuan–Jingyuan segment of the Liupanshan Fault, the Hasishan–Machangshan segment of the Haiyuan Fault, the Kuban Mountain segment of the Altyn Tagh North Marginal Fault, the Yumen and Sunan segments of the Qilian North Marginal Fault, the Tianshui and Luanfeng segments of the West Qinling North Marginal Fault, the eastern Altyn Tagh Fault Zone, the central–western East Kunlun Fault Zone, the northern boundary of the Qilian Block, the northern Zhuanglanghe Fault, the southern Haiyuan Fault, the northern Liupanshan Fault, and the eastern West Qinling North Marginal Fault Zone.