It’s been just over a year since a devastating earthquake ripped through Nepal, killing 9,000 people and destroying some 600,000 structures.

Now, experts warn Kathmandu and other areas along the Himalayan Frontal Fault could be due for an even more powerful event.

Field research and analysis following the 2015 Nepal earthquake suggests a 124-mile stretch of the fault could be in the stages leading up to a massive earthquake of magnitude 8 or greater, capable of producing fractures 15-30 feet high.

An international team, including researchers from the University of Nevada, Reno, conducted several hands-on analyses of the fault lines in the Kathmandu region since last year’s earthquake

WHAT THEY FOUND Researchers dug two deep trenches near the mouths of major rivers at Tribeni and Bagmati. In Tribeni, roughly 124 miles (200 km) south of Kathmandu, they discovered a scarp – a steep bank – of at least 15 feet (5m) vertical separation between 1221 and 1262 AD. And at the Bagmati site, they found a vertical separation of about 30 feet (10m) or more, formed between 1031 and 1321 AD. The findings indicate the 124-mile stretch of the fault could be in the stages leading up to a massive earthquake of magnitude 8 or greater, capable of producing fractures 15-30 feet high. Researchers say the event would be more destructive than the 2015 Nepal earthquake. Advertisement

According to the researchers, the deadly earthquake and aftershocks last year may even be a ‘warning’ of a more powerful event to come.

An international team, including researchers from the University of Nevada, Reno, conducted several hands-on analyses of the fault lines in the Kathmandu region since last year’s earthquake.

Results of the study are published to the journal Earth and Planetary Science Letters.

The researchers dug two deep trenches near the mouths of major rivers at Tribeni and Bagmati, looking at the structural and radiocarbon relationships, along with the layers of rocks and soil, across the fault in areas where it has produced steep banks in soil deposited by the rivers.

This revealed evidence of earthquake displacement dating back thousands of years.

In Tribeni, roughly 124 miles (200 km) south of Kathmandu, they discovered a scarp – a steep bank – of at least 15 feet (5m) vertical separation between 1221 and 1262 AD.

And at the Bagmati site, they found a vertical separation of about 30 feet (10m) or more, formed between 1031 and 1321 AD.

‘We conducted a number of paleoearthquake studies in the vicinity of Kathmandu in the past year, digging trenches and studying soils and fault lines looking back over the past 2,000 years,’ said Steve Wesnousky, geophysics professor and director of the Center for Neotectonic Studies, who has studied the Himalayan Frontal Fault for 20 years.

‘Coupled with the historical record, it’s apparent the faults are capable of earthquakes far greater than the Gorkha earthquake.’

Researchers dug two deep trenches near the mouths of major rivers at Tribeni and Bagmati, looking at the structural and radiocarbon relationships, along with the layers of rocks and soil, across the fault in areas where it has produced steep banks in soil deposited by the rivers

Red stars show the study sites along Narayani and Bagmati Rivers. Green stars indicate epicenters of 2015 earthquake mainshock (M7.8) and largest aftershock, while yellow dots show epicentres of aftershocks greater than magnitude 4 one day after the Gorkha mainshock

According to the study, funded by the National Science Foundation, the Tribeni site could be approaching, or already in, the later stages of strain accumulation before a large earthquake.

‘The sum of our observations suggest that this section of the Himalayan Frontal Thrust fault, extending about 200 kilometers from Tribeni to Bagmati, may rupture simultaneously, and the next great earthquake near Kathmandu may rupture an area significantly greater than in the Gorkha earthquake,’ Wesnousky said.

‘It is prudent to consider that the fault near Kathmandu is in the later stages of a strain accumulation cycle prior to a great thrust earthquake, much greater than occurred in 2015.

‘In these regards, the 2015 Gorkha earthquake did not diminish the current level of seismic hazard in Kathmandu.’

In Tribeni, they discovered a scarp – a steep bank – of at least 15 feet (5m) vertical separation between 1221 and 1262 AD. And at the Bagmati site, they found a separation of about 30 feet (10m) or more, formed between 1031 and 1321 AD

With this new insight, the researchers are working to determine the seismic hazard in the region, and understand more about the mechanics of fault rupture along major continental thrust faults.

They say the findings suggest an earthquake along this stretch could be much more destructive than the 2015 event.

‘The scenario we developed hypothesizes that the next great earthquake may begin to the west near Tribeni and propagate into the section of fault beneath Kathmandu that did not rupture during the 2015 Gorkha earthquake,’ Wesnousky said.