A STUDY ON FAULTING PATTERN OF EARTHQUAKE AFTERSHOCKS

Abstract

The spatial evolution of two aftershock sequenees from the Friuli area, clustered both in space and time, are examined. The aftershock sequences are divided into subsequences arranged in tempora! order. Por each subsequence, ali the combinations of a fixed number of earthquakes are taken, and the seatter matrix of the coordinates of the events, with respect to their centroid, are calculated. The scatter matrices are selected to obtain the best fitting plane where hypocentres are located. The aftershock sequences are mostly characterized by complex multiple faulting. Thìs geometry is probably caused by the stress focusing of the main shock faultìng with the subsequent reorientation of the main tectonic axes.