ИСТИНА

We investigate spatio-temporal variations of earthquake productivity in subduction zones of Kamchatka, Kuril Islands and Japan. In a time-space volume we characterize earthquake productivity by variation of clustering factor, which is defined as an average of ∆M-productivity. ∆M-productivity is a parameter assigned to each earthquake and it is defined as a number of “offsprings” calculated in a magnitude band M ≥ Mm - ∆M, where M is a magnitude of the “offspring”, Mm is a magnitude of the “parent”, ∆M – constant. “Parents” and “offsprings” are found using nearest-neighbors method. We observe that areas of increased clustering factor in a time scale of ten years are connected to epicentres of large earthquakes, for example, Yuzhno Ozernovskoe (M6.6 29.03.2017), Blizhne Aleutskoe (M7.8 17.07.2017), Shikotan (M8.1 04.10.1994), Tokachi Oki (M8.3 25.09.2003), Tohoku (M9.1 11.03.2011) earthquakes. We select the areas of the increased ∆M-productivity and study the changes of the clustering factor prior to and after strong earthquakes. We observe significant peaks of the clustering factor proceeding large earthquake.