In this paper, take two earthquakes for example. Tuosuohu's on Jan. 7,1937(M=7.5) and Gulang's on May 22, 1927(M=8.0)The anomaly of the length of seismic rupture belt is discussed with the concept of energy balance in fracture mechanics.
Such an anomaly of the length of rupture belt is of great importance in earthquake prediction. If the rupture belt is longer during a large earthquake, the same location can still be considered as a risk zone in the coming tens of years. In reverse, if the rupture belt is shorter, this region can be calm for quite a long period.