'Recent tremors in Delhi-NCR don't signal big event but strong quake can't be ruled out'

recent tremors in Delhi-NCR do t point towards a big event though a strong earthquake cant be ruled, Wadia Institute of Himalayan Geology has said.

It said such tremors are t unusual in Delhi-NCR area, but indicate that strain energy is built up in region.

All earthquakes in Delhi-NCR are due to release of strain energy which has been accumulated as a result of rthward movement of Indian tectonic plate and its collision with Eurasian plate through fault or weak zones, institute said in a statement.

re are so many weak zones and faults in Delhi-NCR: Delhi-Haridwar ridge, Mahendragarh-Dehradun subsurface fault, Moradabad fault, Sohna fault, Great boundary fault, Delhi-Sargodha ridge, Yamuna river lineament, Ganga river lineament, it said. 

Wadia Institute of Himalayan Geology functions under Department of Science and Techlogy.   

Since seismic network is quite good, present micro to mir earthquakes in and around Delhi-NCR could be recorded, it added.

All recent 17 quakes recorded in Delhi-NCR region were of low to medium intensity on Richter scale – April 12 - Delhi (3.5); April 13-Delhi (2.7); April 16 – Delhi (2); May 3 – Delhi (3); May 6 – Faridabad (2.3); May 10 – Delhi (3.4); May 15 – Delhi (2.2); May 28 – Faridabad (2.5); May 29 – Rohtak (4.5 and 2.9); June 1 – Rohtak (1.8 and 3); June 3 - Faridabad (3.2); June 4 – Rohtak (2.1); June 8 - Delhi-Gurgaon border (2.1); June 18 – Rohtak (2.1); June 19 – Rohtak (2.3).  

Of se 17, only quake that occurred at Rohtak was above 4 on Richter scale which falls under medium intensity quake.

historical earthquake catalogue shows that re were strong earthquakes of 6.5 magnitude at Delhi in 1720; 6.8 at Mathura in 1803; 5.5 near Mathura in 1842; 6.7 near Bulandshahar in 1956; 6 near Faridabad in 1960 and 5.8 near Moradabad in 1966 in Delhi-NCR.

Delhi-NCR has been identified as second highest seismic hazard zone (Zone IV).

“Sometimes, a vulnerable zone remains quiet, experiences small magnitude earthquakes that do t indicate any bigger earthquake, or receives a sudden jolt by a big earthquake without any call," statement said

Out of 14 small magnitude earthquakes in Delhi-NCR, Rohtak on May 29 earthquake had magnitude of 4.6, it added.

“Since an earthquake cant be predicted by any mechanism, tremors cant be described as signal of a big event,” it said.

recent events cant be defined as “foreshocks”, it added.

If a big earthquake takes place in a region, all smaller tremors that occurred in immediate past at that region are categorised as foreshocks.

“refore, scientifically all se tremors in Delhi-NCR can be demarcated as foreshocks only after a big earthquake takes place immediately. Though it cant be predicted, a stronger earthquake posing a threat to people and properties cant be ruled out,” institute said in statement.

“Though our understanding, in terms of when, where and with how much energy (or magnitude) an earthquake can occur, is t clear, but vulnerability of a region can be understood from past seismicity, calculation of strain budget, mapping of active faults,” it added.

Since an earthquake cant be predicted by any mechanism, tremors cant be described as signal of a big event, institute added.