## 3 Spatio-Temporal Images of Seismic Gaps
The \(M\geq 4.0\) and \(M\geq 4.3\) earthquake interval images are basically consistent (the quiet period with respect to \(M\geq 4.3\) earthquakes is approximately 835 days, between the \(M4.8\)  
Figure 3: Spatial images of the six M \(\geq\) 4.0 seismic gaps in the study area from 1970 to 2022. Gray circles: earthquakes surrounding the spatial location of the gap; yellow circles: earthquakes ending the gaps; blue circles: earthquakes in the periods between the ends of the gaps and before the strong earthquakes; red circles: strong earthquakes corresponding to the seismic gaps; black thick lines: the margins of six seismic gaps. earthquake in Mangkang, Tibet on 19 October 1993, to the \(M7.0\) earthquake in Lijiang, Yunnan, on 3 February 1996). No. 4 seismic gap (Figure 4d): The quiet period with no occurrence of \(M\geq 4.0\) earthquakes is approximately 419 days, which is longer than the d\(T=400\)-day threshold but less than the 6\(\sigma=430\)-day threshold. However, the \(M\geq 4.3\) earthquake interval images are prominent (the quiet period with respect to \(M\geq 4.3\) earthquakes is 1005 days, from the \(M4.3\) earthquake in Mangkang, Tibet on 13 July 2007, to the \(M4.8\) earthquake in Yushu, Qinghai, on 14 April 2010). No. 5 seismic gap (Figure 4e): There are no \(M\geq 4.0\) earthquakes for approximately 673 days. This is notably longer than the d\(T=400\) day and 6\(\sigma\) 460 day thresholds. The \(M\geq 4.0\) and \(M\geq 4.3\) earthquake interval images are basically consistent (The quiet period with no occurrence of \(M\geq 4.3\) earthquakes is approximately 682 days, between the \(M4.6\) earthquake in Shangri-La, Yunnan, on 29 November 2013, to the \(M5.2\) earthquake in Maduo, Qinghai, on 12 October 2015). Figure 4: \(M\geq 3.7\), \(M\geq 4.0\), and \(M\geq 4.3\) earthquake interval graphs for the six seismic gaps in 1970–2022. Green lines: \(M\geq 3.7\); Red lines: \(M\geq 4.0\); Blue lines: \(M\geq 4.3\); Black dashed lines: threshold lines of d\(T=400\) days; Black solid lines: threshold lines of six time variances of the \(M\geq 4.0\) interval times; #: Number of the seismic gap.In the earthquake interval graph for the No. 1 seismic gap (Figure 4a), obvious patterns are not only noted for the No. 1 gap, but also those for No. 2-No. 4 are prominent (#2, #3, and #4 in Figure 4a). Similarly, in the graph for the No. 2 gap, indicative patterns for the No. 3 and No. 4 gaps are observed (#3 and #4 in Figure 4b). In the graph for the No. 3 gap, patterns indicative of No. 4 and No. 6 gaps are noted (#4 and #6 in Figure 4c). In the graph for the No. 4 seismic gap, patterns for No. 1–No. 3 and No. 5 gaps are found (#1, #2, #3, and #5 in Figure 4d). In the graph for the No. 5 gap, patterns for No. 3 and No. 4 are noted (#3 and #4 in Figure 4e). Finally, in the interval graph for the No. 6 seismic gap, patterns for the No. 3 gap are found (#3 in Figure 4f). The results demonstrated that the six seismic gaps have good spatial overlapping. In particular, the No. 1 and No. 4 seismic gaps demonstrate the best spatial overlapping with other gaps. No. 6 seismic gap (Figure 4f): The quiet period with no occurrence of \(M\geq 4.0\) earthquakes is approximately 577 days, which is significantly longer than the d\(T=400\)-day and \(6\sigma=430\)-day thresholds. Yet, the \(M\geq 4.3\) earthquake interval images are prominent (the corresponding quiet period is 774 days, from the \(M4.5\) earthquake in Muli, Sichuan, on 19 November 2019, to the \(M5.5\) earthquake in Ninglang, Yunnan, on 2 January 2022). In short, the six time variances of the \(M\geq 4.0\) earthquake interval times (\(6\sigma\)) lie between 240 and 460 days (with an average of 380 days). The values are basically equivalent to the defined threshold of d\(T=400\) days (excluding the relatively large difference for the No. 2 seismic gap). In other words, the seismic gap identification results are basically similar regardless of whether the six time variance line or the d\(T\) threshold line is used.