3.1.3. Stress change after the 2022 Menyuan earthquake
Figure 4(b) illustrates the cumulative ΔCFS map at a 10-km depth after 2022 induced by 12 historical earthquakes including the 2022 Menyuan earthquake. Figure 5(a) illustrates the ΔCFS distribution along the Qilian-Haiyuan fault system at a 10-km depth after 2022 due to these 12 earthquakes. Except stress perturbation in the 2022 Menyuan earthquake rupture zone (segment GH in Figure 5) induced by this event, stress on the other segments of the Tianzhu Seismic Gap was almost unchanged before and after 2022 (Figure 5).
The stress was loaded in the segment (with the length of approximately 18 km) between the 2016 Mw 5.9 (No. 9) and 2022 Mw 6.6 (No. 12) Menyuan earthquakes with a peak value of 375.15 kPa (Figure 5(a)) in the western portion of the LLLF (segment AD in Figure 5(a)). However, the stress in the eastern portion (with the length of approximately 50 km) of the LLLF located in a stress shadow with a maximum ΔCFS decrease of -396.24 kPa. This stress shadow was mainly controlled by the 2016 Mw 5.9 Menyuan (-335 kPa) (No.9) and 1927 Mw 8.3 Gulang (No. 11) earthquakes by comparing Figure 5 (a) with Figure 3.
The western portion (with the length of approximately 30 km) of JQHF (segment DE in Figures 4 (b) and 5(a)) also located in a stress shadow with a maximum ΔCFS decrease of -101.18 kPa at its western end. This stress shadow was mainly controlled by the 1927 Mw 8.3 Gulang earthquake (-111.4 kPa ) (No. 12) by comparing Figure 5 (a) with Figure 3. However, The eastern portion (with the length of approximately 35 km) of JQHF was stress loaded with a maximum value of 216.7 kPa at its eastern end, which was mainly contributed by the 1920 Mw 8.5 Haiyuan (No. 10) and 1927 Mw 8.3 Gulang earthquake (192.5 kPa) (No. 11) by comparing Figure 5 (a) with Figure 3.
The stress was loaded in the entire MMSF (with the length of approximately 54 km) (segment EF in Figures 4 (b) and 5(a)) with a peak value of 1035 kPa except for its very eastern tip with a minor stress decrease of -1.53 kPa (Figures 4 (b) and 5(a)). The increased stress on the MMSF was mainly controlled by 1920 Mw 8.5 Haiyuan (No. 10) and the 1927 Mw 8.3 Gulang (No. 11) (996.1 kPa) earthquakes by comparing Figure 5 (a) with Figure 3.
The stress was loaded in the entire LHSF (with the length of approximately 60 km) (segment FB in Figures 4 (b) and 5(a)) with a peak value of 786.68 kPa at its eastern end. The increased stress on this fault segment was mainly controlled by the 1920 Mw 8.5 Haiyuan (No. 10) (772 kPa) earthquake by comparing Figure 5 (a) with Figure 3.