The essence of multifractal detrended fluctuation technique to explore the dynamics of soil radon precursor for earthquakes

Abstract

The present paper deals with the application of multifractal detrended fluctuation analysis technique on soil radon-222 time series data recorded at Earthquake Precursory Observatory at TattaPani, Jammu and Kashmir, India. The earth being a complicated dynamic system composed of diverse rock types subjected to spatially varying stress patterns, understanding seismic activity-induced soil gas anomaly in such a complex scenario calls for using nonlinear statistical techniques. Therefore, we have adopted several multifractal parameters especially the generalised Hurst exponent, scaling exponent as well as the multifractal spectrum of the radon time series to the problem. A 2-month data (November 5 to December 31, 2012) on soil radon taken at 10-min interval show a wide variation from 2.34 to 58.99 kBq/m3 with four prominent fluctuations (>mean ± 2σ). The data consists of several nonlinear features such as fractal structures and long-range correlation. The observed nonlinear characteristics are pointed to seismic-induced physico-chemical instability within the earth’s interior. The estimated local fluctuations or root mean square values greatly assist to distinguish the anomalous pattern present in the recorded time series data.