The Delhi Seismic Zone (DSZ) is a seismically highly active intraplate region that keeps experiencing recurrent seismicity of minor to moderate nature. The seismic activity in the DSZ in recent times has evoked concerns about the vulnerability of the region due to potential earthquakes. Although the spatial distribution of recorded earthquakes gives a fairly good idea about the zone of the seismicity, the information about the underlying crustal structure and seismogenic faults is largely missing. In the present work, we have revisited the MT data acquired at various locations across Haryana to understand whether there are any anomalous features in the crust that might correlate with the seismicity in the western part of the DSZ. The MT data recorded at six groups of sites yielded good impedance tensors in the period range of 0.001–1000 s. A significant result obtained by 2-D inversion of distortion corrected impedance tensors is the presence of a northward dipping electrical conductor (<10 $\Omega$m) from the surface down to about 20–25 km depth. The surface location of this conductor is in the proximity of the northern edge of the inferred Delhi–Sargodha Ridge. The DSZ earthquakes, when projected onto the MT profile, coincide with the north dipping conductor. We infer that the conductor is possibly extending into the DSZ and has an important role in the occurrence of the seismicity, at least in the western part of the region and that the increased electrical conductivity is possibly due to the presence of crustal fluids.
Volume 132, 2023
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