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(a)
(b)
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Figure 5.7 Spatiotemporal patterns of large earthquakes in North China in the past 700 years. The
panels show earthquakes (epicenters indicated by dots) during various periods. Large dots with light
rims are large earthquakes discussed in the text. After Liu et al . ( 2011 ) .
5.6.2 Fault coupling and interaction
The spatiotemporal pattern of earthquakes in North China is much more complex than that
at plate boundaries. Large earthquakes roamed between widespread fault systems. Is this
roaming a random effect of long recurrence times on different faults? Or could these large
earthquakes be related to each other through mechanical coupling and interaction between
remote fault systems?
One approach is to study the stress links between these earthquakes. Wang et al .( 1982 )
calculated the stress perturbations of the earthquake sequence in North China during the
past 700 years and suggested that the subsequent events were linked to the previous ones.
Shen et al .( 2004 ) calculated the changes of Coulomb stress by the 48 M
6.5 events
following the 1303 Hongdong earthquake, and concluded that 39 of them occurred in
places where stress was elevated by previous earthquakes.
Another approach is to compare the seismic moment release on these fault systems. For
a system of mechanically coupled fault zones, the total moment release rate should stay at
a certain level, with the moment release rate of individual fault zones being complementary
with each other (Dolan et al ., 2007 ; Luo and Liu, 2012 ) . Liu et al .( 2011 ) showed that the
moment release between the Weihe and Shanxi rifts seems to be complementary to each
 
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