Remarkable changes in the distribution of the order parameter of seismicity before mainshocks

Solid State Section and Solid Earth Physics Institute, Physics Department, University of Athens Panepistimiopolis, Zografos 157 84, Athens, Greece, EU

Received: 27 August 2012
Accepted: 24 October 2012

Abstract

By analyzing in natural time the Southern California Earthquake Catalog (SCEC) during the period 1979–2003, the probability distribution of the order parameter of seismicity is studied. Remarkable changes in the feature of this distribution are identified well before the occurrence of the three major mainshocks reported by SCEC: Landers in 1992, Northridge in 1994 and Hector Mine in 1999. In addition, just before the occurrence of these mainshocks, i.e., for 100 successive events of magnitude M ⩾ 2.0 before each of them, their scaled order parameter probability distributions almost collapse onto a single curve and share over two orders of magnitude a characteristic “exponential tail” reflecting non-Gaussian fluctuations.