UCL Discovery

Abstract

We investigate the time self-similarity properties of seismicity in the Hellenic are, which is one of the most rapidly deforming and seismically active regions of the Mediterranean area. The presence of time-scale-invariance properties in the shallow and intermediate depth seismicity is revealed. In particular, 1/f(beta) fluctuations are detected from the analysis of earthquake sequences using the counting statistics methodology. The shallow seismicity is characterized by a time clustering effect and shows a beta value that is a typical fingerprint of self-similar behaviours, whereas the intermediate seismicity can be considered as a realization of a purely poissonian process. The investigations cover instrumentally recorded earthquakes occurring between 1964 and 1996, and the analyses have been carried out, selecting different magnitude thresholds. The beta value for shallow seismicity decreases from almost 0.5 to 0.2 as the threshold magnitude increases from 3.3 to 4.5. (C) 2000 Elsevier Science B.V. All rights reserved.