甘肃及邻区地震空区预报效能分析OA

We analyze the prediction effectiveness of seismic gaps before MS≥5 earthquakes in Gansu region from 1984 to 2023.The results show that seismic gaps in Gansu and its adjacent regions have an accuracy rate of 0.75,a false rate of 0.25,and a missing rate of 0.38 for forecasting moderate-strong earthquakes in Gansu.The R-value is 0.5,which exceeds the R0 value of 0.23 at the 97.5％confidence level.This demonstrates that seismic gaps have relatively good forecasting capability for moderate-strong earthquakes in Gansu.The mainshocks generally occurred inside the seismic gaps or near their edges,and the duration of these seismic gaps does not exceed 8 years.The number of broken and unbroken seismic gaps before mainshocks are comparable.The probability of the mainshock oc-curring within 1 year after the broken gap is about 89％,and about 67％within 4 months.There is no obvious correlation existed between the duration of seismic gap and the mainshock magnitude.Howev-er,there is a linear relationship between the minimum magnitude of seismic gap with initial magnitude of ML3.0～4.0,and the long axis of seismic gap has a good correlation with the mainshock magnitude.The seismic gap can be used as one of the important indicators for predicting moderate-strong earthquakes in western Qilian mountains,the southeastern part of eastern Qilian mountains and Minxian-Diebu section.It is also a significant indicator for predicting MS≥6 earthquakes in Gansu.The probability of two seismic gaps appearing before mainshock is very high,and the mainshock is most likely to occur within 4 months after the broken gap,located inside or near the overlapping re-gion of the two seismic gaps.