Geomagnetic Signatures of Moderate Earthquakes from Kumaun Himalaya, India

In this study, a statistical analysis of ground geomagnetic data has been attempted to extract the seismo-electromagnetic (SEM) signatures associated with moderate earthquakes in the region of the seismic gap in the Kumaun Himalaya, Uttarakhand, India. We applied the discrete wavelet transform (DWT) method to the geomagnetic data to identify the ULF energy of the signal. The ULF energy obtained in the central frequency range of 0.01 Hz was further filtered to extract the anomalous ULF energy, which is associated with pre-earthquake processes. We also applied multifractal analysis to the geomagnetic data to classify the complexities in the signal, which are indicative of the seismotectonic environment. We observed enhancements in the ULF energy anomalies associated with large-magnitude earthquakes occurring in the western part of Nepal, even over large epicentral distances (~120 km). The multifractal analysis shows the overlap of anomalies in the Hwp and Hwn signatures in most cases, which suggests that multiple mechanisms generate low- and high-frequency components in the anomalous data. This reflects the complex nature of seismicity in this region of the Main Central Thrust (MCT).