Spatiotemporal variations of the b values following the 2019 Mw 7.1 Ridgecrest earthquake sequence

Abstract

b value proposed in the Gutenberg-Richter (GR) law is one of fundamental physical parameters in statistical seismology, which has widely been applied in earthquake prediction, regional stress analysis and earthquake physics. Following the 2019 Mw 7.1 Ridgecrest earthquake sequence, a large number of aftershocks have been observed along the earthquake faults and available publicly. We conducted aftershock decaying analysis of these datasets based on the GR law for the spatiotemporal b values within the fault zone. The results show that the b values along the fault zone turn out homogeneous at a low level of ~ 0.6 right after the mainshock, while they generally increase with time toward a high level of ~ 1.0 within three months. Meanwhile, after the first few weeks the distribution of the b values along the faults presents strongly heterogenous in space, where the recovery speeds of the b values on individual fault cells vary dramatically along both the strike and depth. By contrast to geodetic observations, the variable afterslip processes along the faults, which was controlled by the fault frictional properties, could be responsible for the b value variation. Therefore, the b values could have potentials for the fault frictional properties, which deserve special care in the sense of earthquake prediction.