The 7.3 magnitude event and the subsequent tremors that rocked Nepal on Tuesday were aftershocks and could not be construed as fresh earthquakes, a seismological expert said.
Head of the Seismological Observatory at the CSIR-National Geophysical Research Institute, Dr. D. Srinagesh said there were nine aftershocks till 19.30 hrs on Tuesday, including the biggest one (7.3 magnitude) since the April 25 earthquake of 7.8 magnitude. He said all the events occurred on the eastern extremity of the April 25 rupture, indicating that they were on the same fault rupture.
Had there been a fresh earthquake on a new fault, many aftershocks would have occurred along a larger length of the fault. Usually a 7.8 magnitude earthquake would rupture a length of 150-200 km, which was observed in the April 25 event.
No similar thing had happened on Tuesday and all the events were concentrated in a few kilometres on the eastern end of the April 25 fault zone.
Besides the 7.3 magnitude event, the other aftershocks on Tuesday, ranged from 4.2 to 6.3 magnitude.
“Normal behaviour”
Another seismologist Dr. R.K. Chadha termed the occurrence of the aftershocks as “normal behaviour” after a major quake. He said the region was trying to attain equilibrium by expending the remaining energy.
