Analysis of spatiotemporal variations in b-values before the 6.8-magnitude earthquake in Luding, Sichuan, China, on September 5, 2022

Abstract Using the earthquake catalog provided by the Sichuan Earthquake Network Center, spatial and temporal b-value scans were calculated for large- and small-scale regions based on assessing the completeness of the earthquake catalog and aftershock removal. The results show that (1) b-values in the large-scale region ranged from 0.689 to 1.169, with a mean value of 0.928, while the b-values in the small-scale region ranged from 0.694 to 1.223, with a mean value of 0.925. The b-values in the study area were below the mean value before the medium and strong earthquake occurrence, and all exhibited the anomalous feature of a sudden drop-low peak rise. (2) The sliding rate of the northwest section of the Xianshui River Fracture Zone was higher than that of the southeast section; therefore, a large amount of stress was accumulated in the mill-west section of the southeast section, leading to a 6.8-magnitude earthquake in Luding. Before the earthquake, the study area was a low b-value area. The b-value decreased within a short period after the earthquake, dividing the area into concave and convex bodies. This area still has a future risk of moderate to strong earthquakes. (3) The error in the b-values for most of the earthquakes in the large- and small-scale regions is between 0.05 and 0.15, and only individual grid points have larger b-value errors (>0.2), indicating high confidence in the information. In addition, when conducting a b-value study, choosing a suitable study area is important to avoid missing the b-value anomaly area.