Seismic activity characteristics of the Chinese continent based on a “hybrid” probability forecasting model

A crucial aspect of operational earthquake forecasting research involves constructing a predictive model capable of assessing its efficacy while aligning with the regional seismic activity characteristics. This study delineates the Chinese continent, characterized by complex seismotectonics, into six distinct zones: Northeast, North China, South China, North–South Zone, Xinjiang, and Xizang. Three earthquake probability forecasting models are employed: the relative intensity model (RI), moment ratio model (MR), and simple smoothed seismicity model (Triple-S). Utilizing seismic catalog data from the China Earthquake Networks Center dating back to 1970, with an “anomaly learning period” spanning 10 years and a step length of 1 year, a retrospective sliding forecasting analysis is conducted for earthquakes of magnitude Ms 5.0 or greater over intervals of 3 and 5 years. The efficacy of the forecasting models is assessed through the Molchan chart and T-test methods. Model parameters are finetuned to determine the optimal computational parameters for the three forecasting models. A composite probability forecasting model, adaptable across different time scales and specifically tailored to the seismic activity characteristics of the Chinese continent, is developed. Analysis of seismic activity over the past decade offers insights into the current landscape. This analysis highlights that the high-risk areas identified by the composite model are consistent with previous findings and correlate well with actual earthquake occurrences in the Chinese continent in 2023.