Present-day crustal strain and major fault slip rates in North China determined using GNSS observations

Abstract

• A strain model and an elastic block model of North China were established. • The western Ordos and the northern North China exhibited larger strain rates. • The NNE- and NWW-trending faults showed dextral and sinistral slip respectively. • The fault deformation in North China was controlled by neighboring blocks. North China is characterized by numerous faults, where many earthquakes were recorded. However, the fault slip and crustal deformation mechanism underlying the effects of neighboring block motions remain poorly understood. In this study, we first constructed a strain model using global navigation satellite system (GNSS) velocities to analyze the relationship between seismicity and strain. We then constructed a block model based on the fault distribution and GNSS observations to obtain fault slip. The strain and fault slip rates were then used to determine the crustal deformation mechanism in North China. The strain model suggests the western border of the Ordos Block and the northern North China Plain had larger maximum shear strain rates. These areas are located in a transition between positive and negative dilatation rates, which indicate intense crustal deformation. Based on the block model, we found the NNE-trending faults were dominated by dextral slip. The northern and southern borders of the Ordos Block indicate left-lateral motion (0.4–2.5 mm/a), while its western and eastern margins exhibited right-lateral slip (1.0–3.0 mm/a). The periphery of the Ordos Block exhibited normal slip (0.2–3.2 mm/a), except at the southwestern tip. These results suggest that the eastward extrusion of the Tibetan Plateau caused left-lateral shear in North China, which led to sinistral slip of NNE-trending faults. The northward expansion of the northeastern Tibetan Plateau also contributes to sinistral slip along the northern and southern margins of the Ordos Block, as well as dextral slip along its western and eastern margins.