## 3 Spatio-Temporal Images of Seismic Gaps  
Images of the \(M\geq 4.0\) seismic gap between the \(M4.2\) earthquake in Luhuo, Sichuan on 3 June 2020, and the M5.5 earthquake in Ninglang, Yunnan, on 2 January 2022 (hereafter referred to as No. 6 gap), are taken as the reference (Figure 3f). A seismic gap is defined as a quiet period lasting d\(T\geq 400\) days with no occurrence of \(M\geq 4.0\) earthquakes. All records since 1970 in the study area were studied to identify other five similar \(M\geq 4.0\) seismic gap images in history (Figure 3a-e). They are described as follows. No. 1 seismic gap: between the \(M5.5\) earthquake in Rangtang, Sichuan on 8 November 1970, to the \(M5.2\) earthquake in Kangding, Sichuan on 8 April 1972, with a 517-day quiet period with no \(M\geq 4.0\) earthquake occurrence. No. 2 seismic gap: from the \(M4.7\) earthquake in Yanyuan, Sichuan on 13 August 1986 to the \(M5.5\) earthquake in Ninglang, Yunnan, on 10 January 1988, with no occurrence of \(M\geq 4.0\) earthquakes for approximately 514 days. No. 3 seismic gap: between the \(M4.2\) earthquake in Ninglang, Yunnan on 17 December 1993 and the \(M7.0\) earthquake in Lijiang, Yunnan on 3 February 1996, with no occurrence of \(M\geq 4.0\) earthquakes for approximately 777 days. No. 4 seismic gap: from the \(M4.3\) earthquake in Mangkang, Tibet on 13 July 2007, to the \(M4.2\) earthquake in Ganzi, Sichuan, on 6 September 2008, with an approximate 419-day quiet period with no \(M\geq 4.0\) earthquake occurrence. No. 5 seismic gap: between the \(M4.6\) earthquake in Shangri-La, Yunnan, on 29 November 2013, and the \(M4.2\) earthquake in Zuogong, Tibet on 3 October 2015, with a roughly 673-day quiet period. The spatial dimensions and semi-major-axis directions (spatial distributions) of the six seismic gaps are similar. Their semi-major axes lie in the NNW direction. Figure 2: (**a**) The epicenter distribution, (**b**) incremental (solid black circles) and cumulative (hollow black circles) frequency-magnitude distributions graph, and (**c**) the M-t curve of \(M\geq 4.0\) earthquakes in the study area from 1970 to 2022. To evaluate the impact of the lower magnitude limit on seismic gap identification, earthquake interval graphs (d\(T\)-t) with three different lower limits, i.e., \(M\geq 3.7\), \(M\geq 4.0\), and \(M\geq 4.3\), were plotted separately for each seismic gap (Green lines: \(M\geq 3.7\); Red lines: \(M\geq 4.0\); Blue lines: \(M\geq 4.3\)). In the plots, threshold lines of d\(T\) = 400 days (Black dashed lines)and lines indicating the six time variances of the \(M\geq 4.0\) interval times (6\(\sigma\), Black solid lines) are added (Figure 4a-f). As shown in the figures, for the six seismic gaps (No. 1-No. 6), there are no notable patterns observed in the interval graphs for \(M\geq 3.7\) earthquakes. However, obvious patterns are observed for \(M\geq 4.0\) or \(M\geq 4.3\) earthquake intervals. The results suggest that \(M=4.0\) is the lower limit for identifying seismic gap images. No. 1 seismic gap (Figure 4a): The quiet period with no occurrence of \(M\geq 4.0\) earthquakes lasts approximately 517 days, which is significantly longer than the d\(T\) = 400-day and 6\(\sigma\) = 350-day thresholds. The \(M\geq 4.0\) and \(M\geq 4.3\) earthquake interval images are completely consistent (the quiet period with no occurrence of \(M\geq 4.3\) earthquakes is 517 days). No. 2 seismic gap (Figure 4b): The quiet period with no occurrence of \(M\geq 4.0\) earthquakes is approximately 514 days, which is remarkably longer than the d\(T\) = 400-day and 6\(\sigma\) = 240-day thresholds. Furthermore, the \(M\geq 4.0\) and \(M\geq 4.3\) earthquake interval images are perfectly consistent (the quiet period with respect to \(M\geq 4.3\) earthquakes is 514 days). No. 3 seismic gap (Figure 4c): There are no \(M\geq 4.0\) earthquakes for approximately 777 days. This is considerably longer than the d\(T\) = 400 day and 6\(\sigma\) 370 day thresholds.