NCS conducting surveys to study quakes in Delhi-NCR: MoES

The National Centre for Seismology (NCS) has started a geophysical survey over the Delhi region for accurate assessment of seismic hazards, following tremors in the NCR last year.

The NCS will also carry out analysis and interpretation of satellite imageries and geological field investigations for locating the faults in the Earth’s surface, the Ministry of Earth Sciences said. Both the field surveys, geophysical and geological, are expected to be completed by March 31.

Further, the seismic network in Delhi and surrounding areas has been strengthened after the tremors in 2020 to improve the accuracy of epicentre location to 2 kilometres, the MoES said.

The NCS is a body under the Ministry of Earth Sciences. Delhi experienced four small earthquakes during April – August 2020, with the first event of magnitude 3.5 on April 12 in the northeastern boundary of Delhi. These earthquakes were followed by a dozen micro-events and a few aftershocks.

Soon after the second event of magnitude 3.4 on May 10, the MoES held a detailed discussion with experts to address the ongoing earthquake activity. “It was felt that it is necessary to characterise 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,” the MoES said.

The seismic network in Delhi and its surrounding areas 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.

Data from these stations are received in near real-time and used for locating the micro and small earthquakes in the region. “A geophysical survey, namely, Magneto-telluric (MT) is also being conducted over the Delhi region,” the MoES said. Magneto-telluric (MT) is a geophysical method which uses natural time variation of the Earth’s magnetic and electic fields to understand geological structure and processes.

These measurements are being conducted across three major seismic sources, namely the Mahendragarh-Dehradun Fault (MDF), Sohna Fault (SF) and Mathura Fault (MF). This will help ascertain the presence of fluid, which generally enhances the possibility of triggering of earthquakes. This survey is carried out in collaboration with the Wadia Institute of Himalayan Geology (WIHG), Dehradun.

Analysis and interpretation of satellite imageries and geological field investigations for locating the faults are also being carried out, the MoES said. “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,” the MOES said.

The study is being conducted by the NCS in collaboration with Indian Institute of Technology (IIT), Kanpur.