Analysis of the current activity of the Red River fault based on GPS data: new seismological inferences

To study the seismicity of the Red River fault, observational GPS data from the Crustal Motion Observation Network in China from 1999 to 2018 were selected to calculate the characteristics of strain accumulation based on interpolation. The block-dislocation model was used to study the slip rate, locking degree, and slip deficit of the Red River fault. We used the negative value of the product of the obtained fault slip deficits and time to calculate the fault’s interseismic Coulomb stress accumulation rate. The results revealed that the fault’s dextral strike-slip rate of its northern section is 4.7 mm/year, which is higher than that of its middle and southern sections. The surface expansion rate is mainly manifested by alternating high values of surface expansion and low values of surface extrusion. The maximum shear strain rate, locking degree, slip deficit, and loading rate of interseismic Coulomb stress are all measurably higher in the northern section. In the middle section, the dextral strike-slip rate, surface expansion rate, maximum shear strain rate, and slip deficit are all lower. In the southern section, the slip deficits are large but the locking degree is lower, the maximum shear strain rate is low but high in the surrounding area, and the interseismic Coulomb stress in most parts is positive. The moderate or strong earthquakes probably occur in the northern part of the Red River fault and rarely occur in the middle section, but there is risk of moderate or strong earthquakes in the southern section.