Application of Fracture Induced Electromagnetic Radiation (FEMR) in Deciphering Recent Stresses and Detecting Landslide-Prone Slip Planes.

The technique of Fracture Induced Electromagnetic Radiation (FEMR) has steadily attained an increasing amount of interest in the past decade in the realm of geosciences due to its ability to determine potential active faults, their locations, their frequencies of occurrence along with the determination of their directions of crustal surface stresses. The FEMR technique comes with such potential where geogenic EMR pulses increase anomalously few days/hours prior to an earthquake and damp down immediately after. The attenuation of FEMR pulses is much less as compared to seismic waves making it a more efficient precursor to potential tectonic activities. The phenomenon is generated when charges in the crust of the Earth are built up as a function of the increase in stress. The "Process zone" at the crack tip contains numerous microcracks oriented in accordance with the fracture. The stresses are concentrated anomalously at the crack tip resulting in the propagation and coalescence of microcracks which eventually leads to a macro failure. We have used this technique to study the active tectonics as well as to calculate the orientation of principal horizontal near-surface stresses along the Narmada-Son lineament (NSL) focussing on a stretch of 600 Km between Khandwa-Itarsi-Jabalpur, Central India. In this study, we have taken a total of eighteen horizontal stress measurements along the aforementioned stretch of 600km with orientations varying from N15ºE to N170ºE with a mean azimuth of N85ºE. The local variation in stress azimuth is attributed to the change in fault orientation manifested by the change in the flow path of the Narmada River and the change in its fault escarpment strike. This technique can also be exploited for predicting potential weak slip planes which may eventually lead to small scale landslides. Anomalously high amplitudes of EMR values are obtained in the regions of high "activity" which consist of weak slip planes that can be considered to be potential zones of landslides. Therefore, we aim to build upon the forecasting abilities of the technique of FEMR as an effective alert system which would add great impetus in ensuring an active evacuation approach to help mitigate the after-effects of such natural calamities.