A complexity measure in natural time analysis identifying the accumulation of stresses before major earthquakes

Abstract

Here we suggest a new procedure through which one can identify when the accumulation of stresses before major earthquakes (EQs) (of magnitude M 8.2 or larger) occurs. By analyzing the seismicity in the frame of natural time, which is a new concept of time introduced in 2001, we study the evolution of the fluctuations of the entropy change of seismicity under time reversal for various scales of different length i (number of events). We find that anomalous intersections between scales of different lengths i are observed upon approaching an extraordinary major EQ occurrence. The investigation is presented for the seismicity in Japan since 1984 including the M9 Tohoku EQ on 11 March 2011, which is the largest EQ ever recorded there.