THE GENERALIZED OMORI LAW: MAGNITUDE INCOMPLETENESS OR MAGNITUDE CLUSTERING

Abstract

The investigate the aftershock decay soon after the largest ten sequences occurred in Southern California in last 20 years. We show that this decay becomes independent on the mainshock magnitude MMand on the lower magnitude threshold MIif time is rescaled by an appropriate time scale fixed by the difference MM– MI. This result supports the idea that the missing of recorded earthquakes in first part of aftershock sequences is not an artefact due to catalog incompleteness but a real physical effect. We show that a recently proposed dynamical scaling relationship can reproduce the aftershock decay experimentally observed. This approach gives prediction also in agreement with recent results for the organization of aftershocks after small or intermediate magnitude mainshock in Japan.