4.1. The delayed 2022 Menyuan earthquake
In order to investigate the relation between the three Menyuan
earthquakes: the 1986 (Mw 6.0) (No. 8), 2016 (Mw 5.9) (No. 9), and 2022
Mw 6.6 (No. 12) earthquakes, we demonstrated the stress change on the
2022 Menyuan earthquake rupture induced by the 1986 and 2016 Menyuan
earthquakes before 2022. We found that the 1986 earthquake decreased the
ΔCFS of -2.886 kPa on the 2022 earthquake hypocenter. However, the 2016
earthquake increased the ΔCFS of 0.208 kPa on the 2022 earthquake
hypocenter, which supports the previous proposal by Peng et al. (2022)
that the 2022 earthquake was triggered by the 2016 earthquake due to
stress loading on the 2022 earthquake rupture.
However, the entire 2022 Menyuan earthquake rupture located in a stress
shadow with a negative stress (before 2022) of -15.38 kPa on the 2022
Menyuan earthquake hypocenter by considering the cumulative ΔCFS
resulting from 11 historical earthquakes (Nos. 1-11) during the period
from 1920 to 2022. Generally, earthquake activity in stress shadow zone
is prohibited by unloaded stress from the perspective of earthquake
interaction (Mallman and Parsons, 2008). This method has been
successfully used to investigate the role of earthquake-induced negative
stress on the decreased seismic activities related to the 1857 Fort
Tejon and 1906 San Francisco earthquakes in the San Andreas Fault system
(Simpson et al., 1988; Harris and Simpson, 1996; Harris, 1998; Freed and
Lin, 2001; Mallman and Parsons, 2008) and low seismicity in the Bhutan
Himalaya (Gahalaut et al., 2011). Based on this finding, we suggest that
the 2022 Menyuan earthquake was delayed because of the unloaded stress
on the earthquake rupture resulting from historical earthquakes
interactions in northeastern Tibet during the past century. By comparing
the stress change on the 2022 Menyuan earthquake hypocenter individually
by 11 historical earthquake (Nos 1-11), we found that this stress shadow
was mainly controlled by the 1927 Mw 8.3 Gulang earthquake.