More than 8,000 people died in the April earthquake that shook Kathmandu, Nepal — the deadliest in the country’s history.
But researchers say the initial 7.8-magnitude earthquake were not nearly as destructive as it could’ve been. The fault line, which had been locked for at least 10 years, came apart relatively easily, destroying taller buildings but sparing smaller homes.
Jean-Philippe Avouac, one of the lead authors of both studies and a geology professor at Cambridge University, explained that because of the previous quake, it’s now far easier for the chunks of land beneath the region — which move during a quake like the teeth of a zipper — to “slip” during future quakes.
“We can tell you that for sure this area where the fault has been locked will have to slip during earthquakes in the future,” Avouac told Business Insider.
Avouac also said that the April quake could have done far more damage than it did, because the land separated smoothly, without a lot of energy exerting friction on surrounding areas.
“The onset was very smooth, not a very abrupt rupture,” he said. “This is relatively soft compared to earthquakes that generate a lot of high frequency waves which are more destructive.”
Thanks to readings from geology instruments that had been in place in the region for the decade before the quake hit, researchers were able to get the clearest picture of what happened that they have ever seen, Avouac said. And it could help explain future quakes and possibly help them prepare for what’s to come.
“This is the first time we have had such a nice record of a megathrust, he said. “And it could be that what we’ve observed here would apply to the Himalayan megathrust elsewhere.”
So far, only a portion of the 1,200-mile fault that runs along the Himalayas has unzipped, shown here in yellow:
Despite the severe damage it caused, the entire quake lasted just 50 seconds. Of course, when it happened, the entire faultline didn’t move all at once — earthquakes happen like a zipper, so each piece of land only moves for a few seconds at a time. (Geologists estimate these fragments of Earth moved for about six seconds each). These movements are called slips.
Now that the fault is partially unzipped, it’s likely it will lead to more earthquakes more powerful than the ones we’ve seen.
“Unfortunately we can’t tell you when there will be other earthquakes in the Himalayas,” Avouac said. “…We can … tell you that the kind of magnitude that you can have in the Himalayas is probably of the order of 8.5, the really large earthquakes.”
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