“Strain release in the Circum-Pacific Belt, Chile: 1960”

Abstract

The strain release in the Chilean earthquake sequence starting on May 21, 1960, shows a concentration toward the northern and southern ends of the aftershock area. The segment containing decreased activity is slightly displaced in the interval of 32 months following the start of the sequence. The strain release characteristic exhibits two branches, one due to the release of shear strain, the other due to the release of compressional strain, clearly separated in time. The strain release in the aftershock sequence occurs in the oscillatory manner previously found for a number of aftershock sequences. The seismic activity in South America, south of 10°S, during 40 months preceding the Chilean earthquake sequence, shows a repeated northward migration of the maximum strain release, the migration velocity increasing with time toward the start of the sequence. Four migration cycles can be observed, the pattern of which is strongly influenced by the beginning of the Chilean earthquake sequence.