5.3 Comparison of Coseismic Slip to the July 22, 2020, Mw7.8
Simeonof Earthquake
Figure 6 shows the coseismic slip contours of our preferred 120km
coseismic rupture model for the 2021 Chignik earthquake, and the 2020
Simeonof earthquake from Xiao et al. (2021). Aftershocks that followed
both earthquakes are shown. The July 21, 2020 Mw7.8 Simeonof Shumagin
earthquake is thought to have ruptured to greater depth alongat the
subduction zone interface (e.g., Shillington et al. 2022), and also have
has a deeper aftershock region, than the Chignik earthquake. That
greater depth only applies to the western half of the 2020 rupture. This
difference in the down-dip extent of the coseismic rupture plane, as
well as the down-dip extent of aftershocks might indicate a significant
frictional property difference (e.g., Shillington et al., 2015; Li et
al., 2018; Becel et al., 2017) between the Semidi and the Shumagin
segments, as suggested by the interseismic coupling studies (e.g.,
Drooff and Freymueller, 2021; Xiao et al., 2021)