A review of the seismicity and seismotectonics of Delhi and adjoining areas

Understanding of seismicity and seismotectonics of Delhi and adjoining areas is essential as these areas lie in the seismic zone IV and are geologically confined to the Delhi Fold Belt (DFB), juxtaposed to the Himalayan Frontal Thrust Fold Belt. Owing to the set-up, seismicity in this area is ascribed to the Himalayan Thrust System and activation of DFB Fault Systems. Considerably improved instrumental seismic monitoring in this area and data analysis had resolved three regions of pronounced seismicity that lie close to Sonepat, Rohtak and western part of the NCT Delhi, attributed to activation of various portions of the fault systems of the DFB. Based on seismic telemetry network data, the seismicity pattern analysis revealed that the Mahendragarh Dehradun Sub-Surface Fault (MDSSF) and Delhi Sargodha Ridge (DSR) are the two major zones of structural importance for the nucleation of seismicity in this region. These revelations were corroborated with the fault plane solution of the earthquakes. The dominant mechanism in nucleation of seismicity in DFB is the thrust with minor strike slip. The seismicity and seismotectonics of Delhi and adjoining areas endemic to activation of DFB is reviewed and presented in this paper.