Spatio-temporal variation in earthquake activity, prior to several post-1950 earthquakes with magnitude ≧ 8.0 in the circum-Pacific area, has been examined in order to identify a common precursory pattern. Strain energy ΣE released in the rupture zone of these great earthquakes was computed for every year between 1910 and the time of the great earthquake. An examination of strain energy release as a function of time shows that maximum strain energy Σ(EB) is released in the rupture zone at a time which depends on the magnitude (M) of the subsequent great earthquake. The ratio of strain energy ΣEM released in the great earthquake to the strain energy ΣEB varies between 3 and 30, i.e., this burst of activity is equivalent to a single earthquake of magnitude between 12 to 2 units less than the magnitude of the great earthquake. The amount of maximum deformation and the time at which it occurs appears to depend on the magnitude of the great earthquake.

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