Variation Features of b-Value Before and After the 2021 Maduo Mw 7.4 Earthquake

  Objectives  The b-value in the Gutenberg-Richter relation is often used as an essential indicator for estimating the magnitude of regional stress, and it plays a vital role in evaluating the probability of earthquake occurrence. At 02:04:11 on May 22th, 2021, an Mw 7.4 earthquake occurred in Maduo County, Qinghai Province. The Maduo earthquake unexpectedly occurred inside the Bayan Har block, and located in Kunlun-Jiangcuo fault, which is a secondary fault in south of the East Kunlun fault.

  Methods  To reveal the seismogenic environment of the source region before the Maduo earthquake and the evolution of the aftershocks, the distribution and change of b-value before the Maduo earthquake are investigated by using the earthquake catalog provided by the China Earthquake Networks Center from January 1, 2009 to May 20, 2021. The catalog includes 32 230 well-located events with a complete magnitude.

  Results  The results indicate that b-value in the source area is extremely low before the 2021 Maduo earthquake, indicating a significant stress accumulation in the source region. Moreover, there is a noticeable decrease in b-value in the source region before the 2021 event.

  Conclusions  The b-value is an essential indicator of the upcoming great earthquake and has excellent potential for predicting a future large earthquake within the block. Moreover, the early b-value variations are of guiding significance to the location prediction of aftershock in the future.