Dynamic Multifractality of Seismic Activity in Northeast India

In recent years, the study of earthquakes has proven to be of great interest, particularly to understand the hidden processes underlying earthquake generation. The multifractal characteristics of frequency–time series of earthquakes of magnitude M ≥ 3 and M ≥ 4 that occurred in Northeast India (NEI) from January 1973 to December 2016 are studied in the present work. The Hurst exponent calculated for the NEI earthquake data is larger than 0.5, presenting long-range correlations and persistent behavior. In the present study, multifractal detrended fluctuation analysis (MFDFA) is used to study the multifractal properties of the data. The results show different shapes of multifractal spectra and corresponding distinct properties. This indicates that the degree of multifractality exhibits strong variation with time, which is associated with the dynamic evolution of earthquake activity in this region. The singularity spectrum is left-skewed and shows a long left tail, suggesting that the multifractal structures are sensitive to local fluctuations of large numbers of events. The singularity spectra of the four blocks of NEI also show a long left tail but with different width of the spectrum, indicating variation in the strength of multifractality in different blocks of the study area.