Please use this identifier to cite or link to this item: http://hdl.handle.net/2122/1420
AuthorsSimeonova, S.* 
Solakov, D.* 
TitleTemporal characteristics of some aftershock sequences in Bulgaria
Issue DateOct-1999
Series/Report no.42/5
URIhttp://hdl.handle.net/2122/1420
KeywordsAftershock
Aftershock decay rate
secondary Aftershock sequences
Subject Classification04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous 
AbstractWe apply statistical analysis to study the temporal distribution of aftershocks in aftershock sequences of five earthquakes which occurred in Bulgaria. We use the maximum likelihood method to estimate the parameters of the modified Omori formula for aftershock sequences which is directly based on a time series. We find that: the maximum likelihood estimates of the parameter p show a regional variation, with lower values of the decay rate in North Bulgaria; the modified Omori formula provides an appropriate representation of temporal variation of the aftershock activity in North Bulgaria; the aftershock sequences in South Bulgaria are best modeled by the combination of an ordinary aftershock sequence with secondary aftershock activity. A plot of the cumulative number of events versus the frequency-linearized time t clearly demonstrates a transition from aftershock to foreshock activity prior to the second 1986 Strazhitsa (North Bulgaria) earthquake.
Appears in Collections:Annals of Geophysics

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