Due to the lack of post-earthquake movement, leading to build-up strain in the faults, the Himalayan region may experience an earthquake far more destructive than the 2015 7.8 Nepal quake that killed 8,000 persons and destroyed parts of the country, says a study.
The 2015 Nepal quake ruptured a 150-km-long section of the Himalayas but did not rupture the Earth’s surface, signifying that only part of the fault had slipped below ground.
In the following days, even the afterslip – post-earthquake movement – produced little surface evidence of continued movement.
The study team used GPS records of surface motions to show that only a little seismic slip occurred on the ruptured fault plane in the six months immediately following the earthquake.
The findings showed that the part of the fault that had not moved remained completely locked, accumulating further strain.
The team estimated that there may be about 3.5 metres worth of strain built into this fault, which the post-earthquake movements did nothing to reduce.
“There was a clear lack of afterslip. That has implications for future great earthquakes, which can tap into this stored strain,” said lead author David Mencin, student at the University of Colorado at Boulder in the US.
This means that below the region, there is a great well of energy still pooled, which the future quakes can result in devastating consequences, Mencin explained in the paper published online in the journal Nature Geoscience.
“There’s no evidence that it will spontaneously rupture in another damaging earthquake. But the strain may fuel a future earthquake starting nearby,” Roger Bilham, professor at University of Colorado at Boulder, said.
He added, “The entire Himalayan arc may host dozens of pockets of strain energy awaiting release in future great earthquakes.”