Geologists say Nepal's last two deadliest earthquakes, one in 1934 that killed thousands and another 81 years later on Saturday, is part of a pattern that occurred centuries before, the BBC reported. 

In the jungles of central Nepal, French researchers digging along the country's main earthquake fault say they found evidence within the ground's charcoal indicating that a set of devastating earthquakes occurred in two areas along the fault in 1255 and then 89 years later in 1344- the same area where the two recent quakes occurred over 700 years later. 

The ancient pattern of duo quakes was discovered weeks before Saturday's magnitude-7.8 earthquake struck between the capital Kathmandu and the city of Pokhara, killing over 4,000 people and counting.

In 1934, a violent earthquake occurred at a part of the fault located east of the capital, killing over 17,000 people, Laurent Bollinger of France's CEA research agency told the BBC.

This indicates that after the '34 quake, stress along the fault accumulated and traveled westward until it cracked under pressure decades later in 2015.   

Carbon-dating of the fault's charcoal showed the same thing happened east of Kathmandu in 1255. Strain within the fault traveled westward until it ruptured again in 1344, the BBC reported.

When researchers realized this, they knew Nepal was likely in for a catastrophic quake.

"We could see that both Kathmandu and Pokhara would now be particularly exposed to earthquakes rupturing the main fault, where it likely last did in 1344, between the two cities," Paul Tapponnier, from the East Observatory of Singapore and Bollinger's colleague, told the BBC.

Though the strain has been released- at the expense of thousands of lives and the destruction of remote villages and historic landmarks- geologists fear Saturday's quake was "not big enough to rupture all the way to the surface, so there is still likely to be more strain stored," Bollinger told the BBC.

"We should probably expect another big earthquake to the west and south of this one in the coming decades."