Scaling and crossover phenomena in anomalous helium sequence

Anomalous temporal fluctuations of helium concentrations in spring emanations have been observed on a number of occasions prior to some major seismic events. Several recent studies have shown that a wide variety of natural systems display significant fluctuations that may be characterized by long-range power-law correlations. We have applied detrended fluctuation analysis (DFA) to characterize preseismic helium anomalies and to probe the relationship between two classes of apparently irregular helium sequences. Application of the DFA technique reveals a crossover phenomenon that distinguishes short-range from long-range scaling exponents; the crossover corresponds to a transition from nonpersistent to persistent traits in the helium time series. Our findings imply a significant statistical correlation between anomalous helium concentration and a fluctuation exponent. This analytical approach appears to be a promising way for identifying anomalous helium fluctuations as signals precursory to an earthquake.