Temporal variations of long-term correlations in seismic activity fluctuations

The scaling behavior of the 1998–2009 seismicity in Guerrero, southern Mexico, was studied by means of the detrended fluctuation analysis (DFA). We found that inter-seismic periods are correlated with a transition in the scaling behavior at about 200 seismic events. Correlations are relatively weak for small time scales. However, for large time scales, correlations are associated with a 1/f fractional process, indicating that the seismicity pattern emerges from a self-organized critical state. Temporal variations of the scaling exponent along years computed from the DFA indicate the presence of a quasi-biennial cycle in the seismicity correlations. This cyclic behavior was apparently triggered by the large 2001–2002 slow slip event in the Guerrero seismic gap. Besides, the significant seismic events (Mw>5) originate, on the average, at deeper regions in each cycle.