Correlation of change in magnetotelluric parameters before and after Sikkim Himalayan earthquakes associated with stress variation

Shankar Konda and Prasanta K. Patro

 The apparent resistivity of MT data sites acquired after 2006, 2007 and 2011 earthquakes attributed an observed change (decrease) is in the range of 10–30%. Strike direction, Polar diagrams, and Phase tensor ellipses support the observed impedance change. The feature of low resistivity zone recognized from geoelectric model with joint inversion of TE and TM mode data acquired after these earthquakes. The ob- served resistivity change is related to combined stress drops at different depth levels in association with strong ground motions induced from 2006, 2007 and 2011 events. The correlation between relative change in observed apparent resistivity and estimated stress drop corrobarate the relation. Alternatively, strong ground motions which caused for greater stress drop level could have been migrated the crustal fluids from compressional to dilatation zones and altered the mechanical and electrical properties resulted in change in resistivity.

 

Regional geo-tectonic map of Sikkim Himalaya showing Magnetotelluric (MT) site locations

Tectonophysics 765 (2019) 205–225

https://doi.org/10.1016/j.tecto.2019.04.034