Fractal analysis of geomagnetic data to decipher pre-earthquake processes in the Andaman-Nicobar region, India

Abstract

Seismo-electromagnetic (SEM) signatures recorded in geomagnetic data prior to an earthquake have the potential to reveal pre-earthquake processes in focal zones. The present study analyses the vertical component of geomagnetic field data from March 2019 to April 2020 using fractal and multifractal approaches to identify the EM signatures in Campbell Bay (CBY), a seismically active region of Andaman and Nicobar. The significant enhancements in monofractal dimension and spectrum width components of multifractal analysis arise due to superpositioned high- and low-frequency SEM field emitted by the pre-earthquake processes. It is observed that the higher-frequency components associated with microfracturing dominating signatures of earthquakes occurring around the West Andaman Fault (WAF) and Andaman Trench (AT), while the lower frequencies, which result from slower electrokinetic mechanisms, have some correlation with the earthquakes around the Seulimeum strand (SS). Thus, the monofractal, spectrum width, and Hölder exponent parameters reveal a different nature of pre-earthquake processes that can be identified, on average, 10, 12, and 20 d prior to the moderate earthquakes, which holds promise for short-term earthquake prediction.