Magnetotelluric studies in the Central India Tectonic Zone: Implications for intraplate stress regimes and generation of shallow earthquakes

• The Central India Tectonic Zone (CITZ) is seismically active since the Precambrian.
• The mechanism for the shallow earthquakes in the western part of CITZ remain unknown.
• The crust below the southern part of the Tapti River has cratonic signatures.
• Mafic–ultramafic bodies beneath the CITZ may be a cause for the shallow earthquakes.
• Strain energy in the crust is related to the Deccan Volcanic activity.

The Central India Tectonic Zone (CITZ) dissects the Indian Peninsula into the northern and southern crustal blocks. The CITZ has been a seismically active region since the Precambrian. Whereas the relatively deep crustal earthquakes near the Narmada faults in the eastern part of the CITZ have been well-investigated, the mechanisms for the shallow earthquakes in the western part remain unknown. Here we present results from a new magnetotelluric study to derive the crustal structure and to understand its implications. Our data show a thick and highly resistive (>500 ohm m) crust in the south of Tapti River, as against a less resistive one in the north. These results in conjunction with heat flow values indicate that the crust below the southern part has stable continental cratonic signatures. On the northern side of the Tapti River, we infer the ascent of basaltic magmas from the mantle into the shallow crust and crystallization into layered intrusions. These mafic–ultramafic bodies could be a potential cause for the shallow earthquakes in the western part of the CITZ. The mafic–ultramafic bodies below the crust of CITZ would locally modify the intraplate stresses, which in turn would facilitate the occurrence of earthquakes due to reactivation of pre-existing faults. Thus, the large accumulation of strain energy in the deep crust beneath the region can be attributed to the presence of high stress bodies emplaced at depth during the Deccan Volcanic activity.