Aging and scaling of earthquake aftershocks

A part of the seismic time series, in which the Omori law for temporal pattern of aftershocks holds, is referred to as the Omori regime. Here the properties of correlation between earthquake events both inside and outside of the Omori regime are studied by analysis of the data taken in southern California. It is found that inside of the Omori regime correlation exhibits the aging phenomenon (with respect to the label of the aftershock, not with respect to time), in marked contrast to the fact that no aging is observed outside of the Omori regime. The scaling nature of aging is also discussed and the form of the function responsible for it is presented. The results seem to indicate that complex fault-fault interactions for aftershocks may be governed by glassy dynamics. (C) 2003 Elsevier B.V. All rights reserved.