New Delhi (NVI): Delhi and National Capital Region (NCR) has experienced four small earthquakes during April—August 2020, followed by a dozen of micro-events and aftershocks, according to the National Centre for Seismology (NCS).
“With the first event of magnitude 3.5 on April 12, in the northeastern boundary of NCT Delhi, during the prevailing lockdown time. These earthquakes were followed by a dozen of micro-events (M<3.0) including, a few aftershocks,” the Ministry of Earth Science said in a statement.
“All these events were located by the National Seismological Network (NSN), being operated and maintained by National Seismological Centre (NCS), Ministry of Earth Sciences,” it added.
The epicenter of these events falls in three different areas, which are north-east Delhi border, 15 km south-east of Rohtak (Haryana) and 17 km east of Faridabad (Haryana).
On May 10, the second event of magnitude 3.4 occurred. In addition to this, the ministry had a detailed discussion with experts to address the ongoing earthquake activity, the statement said.
It was necessary to characterize the earthquake sources in Delhi and surroundings through strengthening of local seismic network and delineation of sub- surface features such as fault, which may cause earthquakes. A fault is a fracture or discontinuity in a volume of rock, it said.
Meanwhile, NCS initiated the seismic network in Delhi and surroundings, which was strengthened by deploying 11 temporary additional stations covering the known faults in the region to precisely locate the earthquakes and their aftershocks for a better understanding of the causative sources, the ministry noted.
“Data from these stations are received in near real-time and used for locating the micro and small earthquakes in the region. The expanded network has now improved the accuracy of the epicenter location to 2 km,” it added.
The geophysical survey, namely, Magneto-telluric (MT) is also being conducted over the Delhi region. Magneto-telluric (MT) is a geophysical method which uses natural time variation of the Earth’s magnetic and electric fields to understand geological (underground) structure and processes.
These measurements are conducted across three major seismic sources, namely Mahendragarh-Dehradun Fault (MDF), Sohna Fault (SF) and Mathura Fault (MF). They ascertain the presence of fluid, which generally enhances the possibility of triggering of earthquakes. However, the survey is carried out in collaboration with Wadia Institute of Himalayan Geology (WIHG), Dehradun.
The statement further informed that, the analysis and interpretation of satellite imageries and geological field investigations for locating the faults are being carried out.
This information along with the results of MT survey will be useful in accurate assessment of seismic hazard. It can also be used for designing the earthquake resistant buildings, industrial units and critical structures like, hospitals and schools etc.
Furthermore, the study is being conducted by NCS in collaboration with Indian Institute of Technology (IIT), Kanpur, the ministry said, adding that, “Both the field surveys, geophysical and geological, are progressing well and are expected to be completed by March 31, 2021.