Abstract
Delhi region in northern India experiences frequent shaking due to both far-field and near-field earthquakes from the Himalayan and local sources, respectively. The recent M3.5 and M3.4 earthquakes of 12th April 2020 and 10th May 2020 respectively in northeast Delhi and M4.4 earthquake of 29th May 2020 near Rohtak (~ 50 km west of Delhi), followed by more than a dozen aftershocks, created panic in this densely populated habitat. The past seismic history and the current activity emphasize the need to revisit the subsurface structural setting and its association with the seismicity of the region. Fault plane solutions are determined using data collected from a dense network in Delhi region. The strain energy released in the last two decades is also estimated to understand the subsurface structural environment. Based on fault plane solutions, together with information obtained from strain energy estimates and the available geophysical and geological studies, it is inferred that the Delhi region is sitting on two contrasting structural environments: reverse faulting in the west and normal faulting in the east, separated by the NE-SW trending Delhi Hardwar Ridge/Mahendragarh-Dehradun Fault (DHR-MDF). The WNW-ESE trending Delhi Sargoda Ridge (DSR), which intersects DHR-MDF in the west, is inferred as a thrust fault. The transfer of stress from the interaction zone of DHR-MDF and DSR to nearby smaller faults could further contribute to the scattered shallow seismicity in Delhi region.
Highlights
Delhi region in northern India experiences frequent shaking due to both far-field and near-field earthquakes from the Himalayan and local sources, respectively
Taking advantage of the quality data generated by the local seismological network, we propose a seismotectonic model of the Delhi region through the integration of seismicity characteristics, the associated structural features and the estimates of strain energy released in the region
We have examined the possibility of Trans Himalayan conductor (THC) as the causative structure of two recent earthquakes, M3.5, 12th April 2020 and M3.4, 10th May 2020
Summary
Delhi region in northern India experiences frequent shaking due to both far-field and near-field earthquakes from the Himalayan and local sources, respectively. Based on fault plane solutions, together with information obtained from strain energy estimates and the available geophysical and geological studies, it is inferred that the Delhi region is sitting on two contrasting structural environments: reverse faulting in the west and normal faulting in the east, separated by the NE-SW trending Delhi Hardwar Ridge/Mahendragarh-Dehradun Fault (DHR-MDF). The National Capital Territory (NCT) of Delhi is located about 250 km away from the seismically active Himalayan collision zone and experiences shaking frequently from far field and near field earthquakes. Three earthquakes occurred in Delhi region (12 April 2020 of M3.5, 10 May 2020 of M3.4 and 29th May 2020 of M4.4), which have been recorded by a dense local network of 15 seismic stations. A comprehensive appraisal (seismological and geophysical) has been conducted to probe linkages within local geological structures of the region and to propose a holistic seismotectonic model
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