'Talking earthquakes' led to fresh tragedy

Do earthquakes talk to each other? A section of geoscientists has claimed a geophysical communication from the April 25 quake in Nepal may have caused the latest 7.3-magnitude temblor near Kodari in the Himalayan country on Tuesday.

“Earthquakes are known to talk to each other. A part of the energy release is used to move rocks while another portion reaches out to the next fault system. The process goes on,” Shyam Sundar Rai, a professor and chair of the Earth Sciences Department at the Indian Institute of Science, Education and Research, Pune, told Deccan Herald.

On April 25, Nepal was struck by a 7.9-magnitude quake, which left a trail of death and devastation in 14 districts, the worst-affected being Sindhupalchowk and the Kathmandu valley.

Tuesday's 7.3-magnitude aftershock was followed by nine smaller ones till the time of filing this report.

Formerly a senior scientist at the National Geophysical Research Institute (NGRI), Hyderabad, Rai researched extensively on earthquakes in the Himalayas.

“Such cascading effects were seen in Sumatra after 2004, and are being observed in Nepal now,” he said. “After the big earthquake in Sumatra in 2004, these cascading quakes continued for several months, in which one fault system impacted the next. It is not very unusual,” he said.

Computer modelling studies carried out by another group of researchers in Bengaluru seem to suggest an eastward direction to the seismic activities. However, the researchers at the Council of Scientific and Industrial Research's Fourth Paradigm Institute are yet to fully evaluate the implications of such a shift, though they think occurrence of two seven-plus-magnitude quakes in the same region is rare.

Several scientists, however, feel it is too early to look for a pattern or propose new theories. “As of now, I have no reason to describe it as anything more than an aftershock,” said NGRI ex-director Harsh Gupta, who retired as secretary to the Ministry of Earth Sciences.

The US Geological Survey described the May 12 temblor as the “largest aftershock” of the April 25 event.

They occur because of seismic instability of the Himalayan region, where the Indian plate is diving under the Eurasian plate at a rate of 4.5 cm every year.