Fractal analysis of the ground-recorded ULF magnetic fields prior to the 11 March 2011 Tohoku earthquake ( M W = 9): discriminating possible earthquake precursors from space-sourced disturbances

摘要: The fractal characteristics of the ultra-low-frequency (ULF) magnetic field variations recorded prior to Tohoku earthquake (EQ) with MW = 9 which happened on 11 March 2011 are studied in this article use detrended fluctuation analysis and Higuchi dimension algorithm. In specific study, we for our calculations only nighttime (LT 3 a.m. ± 2 h) data because their lowest contamination by industrial noise. A key aspect is investigation about any possible correlation ULF or calculated geomagnetic indices. Different preprocessing approaches examined aiming at minimization influences from global phenomena results, while same time retaining scale-invariant character after preprocessing. obtained results imply locally driven change EQ, compatible that has been reported other large EQs.