Interseismic movement along the Luhuo-Daofu section of the Xianshuihe Fault from InSAR and GPS observations

Located on the eastern margin of the Tibetan Plateau, the Xianshuihe fault is a large left-lateral strike-slip fault with high seismic activity. The Luhuo-Daofu segment of the fault is one of a few sections where creep has been observed, but it lacks systematic research on the creep using high-resolution geodetic data. In order to study the interseismic movement characteristics of the Luhuo-Daofu section, we process and integrate the InSAR and GPS data covering the area. The InSAR velocity field and interpolated GPS velocity field are transformed to fault-parallel direction, and the GPS data are transformed into the InSAR reference frame by the bootstrap method. In the data integration process, we prioritize the retention of far-field tectonic movement and near-field high-resolution deformation characteristics. Based on the integrated velocity field, we formulate a simple screw dislocation model which includes shallow creep, intermediate locked and deep slip layers, and use the Markov Chain Monte Carlo method to invert for the fault slip rate, shallow creep and locked depth of the Luhuo-Daofu section. The profile analyses of the InSAR velocity field show obvious surface sinistral-creep in the Luhuo-Daofu section, and the creep rate varies along the strike direction being 1.0 similar to 5.2 mm.a(-1). Specifically, the rate gradually increases initially, followed by a decrease, but then again increases. The creep rate of Luhuo section is significantly lower than that of Daofu section. The screw dislocation modelling indicates that the creep depth of the Luhuo-Daofu section is similar to 9.8 km, the shallow creep rate is 3.27 similar to 4.18 mm.a(-1), and the fault slip rate is 8.12 similar to 9.30 mm.a(-1). The earthquake recurrence interval of the Luhuo segment is 370 similar to 410 years, and the thickness of the locked layer is similar to 1 km, showing a low earthquake risk. The earthquake recurrence interval of the Daofu segment is 59 similar to 65 years, and the thickness of the locked layer is similar to 7.5 km, suggesting that sufficient strain can be accumulated there. The seismic moment released by shallow creep is similar to 1.32 x 10(16) Nm.a(-1), accounting for 23%similar to 38% of the accumulated moment due to tectonic loading. In the past 40 years, the seismic moment in the locked area has reached 3.62 x 10(17) to 7.88 x 10(17) Nm, equivalent to M-W 5.6 similar to M(W)5.9. Therefore its seismic risk is necessarily noteworthy.