On the source time function of the October 13, 1963 Kurile Islands Earthquake

Abstract

The temporal evolution of the source mechanism is retrieved for the October 13, 1963 Kurile islands earthquake by applying centroid moment tensor inversions to successively different narrow frequency windows between 2 and 12.5mHz. The lateral heterogeneity effect is corrected using model M84A of Woodhouse and Dziewonski [1984]. To the first approximation the frequency‐dependent scalar moment follows an ω−2 decay law and the origin time shift is frequency independent, which can be simply explained by an isoscele source time function 140s long and a total moment release of 62 × 1027 dyne.cm. The expansion of the moment rate functions in terms of spline functions enables to retrieve a smooth temporal change of the moment tensor. This second inversion yields a total moment of 71 × 1027 dyne.cm with a peak activity at about 70s after the onset in a total source time of 250s. The mechanism has remained unchanged during the main stage. The occurence of back‐slip to the amount of 6.5% of the total moment is implied for the last 80s.