IIT seismologist says Sunday’s jolt in Nepal was a ‘fresh quake’ not an aftershock

There can be more similar main shocks and the government should take measures based on the correct information.

IIT, Kharagpur professor and an eminent seismologists of the country, Prof Sankar Nath has rejected claims by many that Nepal had received a massive “aftershock” of 6.7 magnitude, nearly 24 hours after the earthquake hit Nepal on Saturday on April 26. The IIT seismologist described the Sunday’s jolt at around 12.45 as a “fresh earthquake” – the second to hit Nepal in two days on April 26 and 27th.

The epi-center of the second earthquake was at 19 km south-southeast of Kodari in Nepal with a magnitude of 6.7, says the senior seismologists. The epicenter of the Kodari earth quake is around 150 km away from the epicenter of the earthquake of 7.9 on Saturday.

Amid widespread confusion over the second jolt in Nepal, IIT (Kharagpur) professor has prepard his report that he would submit to the government of India soon.

Significantly, it was widely reported that the strong shake on Sunday was an ‘aftershock’. “It was not an aftershock, but a main shock triggered by the release of the stress accumulated due to the main shock on Saturday. An after shock cannot take place outside the source origin. And an aftershock is always recorded within 50 to 100 square kilometer of the epicenter of the main shock,” said Nath.

However, the epicenter of Kodari earth quake was recorded at a remote village that is at least 150 km away from the epicenter of the first main shock in Nepal on Saturday. The fresh earth quake on Sunday had two aftershocks. The first aftershock came seventeen minutes after the main quake at 29 km away from south southwest of Kodari in Nepal.

Prof S K Nath of the geology and geophysics department of Kharagpur IIT has 14 stations in Darjeeling and Sikkim to record the data of the earth quakes. “We have 12 stations in Sikkim, a station in Darjeeling and another station in Siliguri. We would submit the data to the ministry of earth sciences and there we would mention it as a main shock.”

Even though the IMD has recorded it as an ‘aftershock’, Prof Nath claimed that USGS has recorded it as a ‘main shock’. The USGS website says, “An earthquake with magnitude 6.7 occurred near KATHMANDU, Nepal at 07:09:08.90 UTC on Apr 26, 2015. This event has been reviewed by a seismologist.”

The earth quake on Sunday also made a strong impact in the region and triggered a second avalanche in the Mount Everest. A Bhatnagar awardee, Prof Nath added, “The second main shock had two aftershocks measuring 5 yesterday .” According to the data recorded, the epicenter of Kodari earth quake was located 17.3 kilometers deep while the first main shock of 7.9 on Saturday was located 11 km deep, said Prof Nath.

The earth quake of April 25 had already more than 45 aftershocks. “The main shock of 25 April had an immediate aftershock measuring 6.6. And since then the aftershocks started becoming weaker. Barring a few, all the aftershocks were recorded below 5 and some shocks were below 4.

After 24 hours of the main shock, there cannot be an aftershock of 6.7 while more than 40 decaying aftershocks already came, explained the Professor.

When contacted, another noted seismologist Prof Ranjit Majumdar also termed Sunday’s jolt as a ‘main shock.’ “It is a main shock. It is a fresh earth quake and not an aftershock that took place on Sunday. The strain gathered due to the first main shock on April 24 was released that triggered a fresh earth quake in the region.

There can be more similar main shocks and the government should take measures based on the correct information. There should be a thorough earth quake study in Bengal, Bihar and Uttar Pradesh region due to its seismic nature.” said Prof Majumdar of Geophysics in Jadavpur University.

Source:: Indian Express