Lithospheric resistivity structure of the 2001 Bhuj earthquake aftershock zone

The Kutch rift zone in the NW India is one of the most seismically active intraplate regions of the world as seen by the occurrence of large earthquakes for many centuries and the unusual persistent aftershock activity following the 26 January 2001 Bhuj earthquake of Mw = 7.7.  Several of the geophysical studies inferred the presence of fluids in the crust of seismically active Bhuj area, but its deep origin is not fully understood. In this context, imaging of the lithosphere structure of the area was carried out using long-period magnetotelluric data (30–10 000 s) to understand the deep origin, nature and upward pathways of the fluids to understand the plausible generation mechanisms of intraplate seismicity in general and specifically for the Bhuj earthquake region.

 

The 3-D resistivity model retrieved from the MT data exhibited two important low resistivity features, that originate from the top of the mantle conductive zone and extends upwards through the crust at a location coinciding with the surface trace of Kutch Mainland Fault (KMF) system. The MT model also showed resistive crustal domains and typify a major part of the crustal section. This study suggests a key role of fluids in intraplate seismicity of the Bhuj region through fluid pressure, which adds to the regional compressive stress regime caused by ongoing India–Eurasia collision and facilitate to attain the critical stress conditions for rock failure in the weak zones. 

Citation

K.K. Abdul Azeez, Kapil Mohan, K. Veeraswamy, B.K. Rastogi, Arvind K. Gupta

and T. Harinarayana; Geophys. J. Int. (2021) 224, 1980–2000; https://doi: 10.1093/gji/ggaa556