Characteristics and predictive significance of spatio-temporal space images of M ≥ 4.0 seismic gaps on the southeastern margin of the Tibetan Plateau

 In the present study, seismic gaps are identified as periods with no occurrence of M ≥ 4.0 earthquake over dT ≥ 400 days. After examining all records in the Sichuan-Yunnan-Tibet-Qinghai junction area on the southeastern margin of the Tibetan Plateau in 1970−2022, a total of six M ≥ 4.0 seismic gaps were identified. Spatio-temporal images of the seismic gaps had similar characteristics and demonstrated spatial overlapping and statistical significance. The quiet periods of the six seismic gaps included 419−777 days (approximately 580 days on average). The semi-major-axis and semi-minor-axis lengths were in the 880−1050 km (approximately 987 km on average) and 500−570 km (about 533 km on average) ranges, respectively. Case analysis results revealed that the images of M ≥ 4.0 seismic gaps were of high significance in predicting M ≥ 6.7 strong earthquakes in the region, and they could be used as a predictive index on a time scale of about 1-0.5 year or less.