Will another big earthquake hit Kathmandu?

Question

Recently, we got the news that the western part of Nepal may be hit by a larger earthquake than that of April 25, because it did release all of its energy. During the earthquake, only the eastern part of Nepal was affected. So I want to know if Kathmandu, i.e. the central part of Nepal, could also be affected by the anticipated earthquake.

Answer 1

From a geological perspective, the short answer is yes. Kathmandu and the central Himalayas are situated directly above the Main Himalayan Thrust (MHT), one of the most active tectonic boundaries on Earth. While the April 2015 Gorkha earthquake (Magnitude 7.8) was devastating, it did not release all the accumulated strain in the region.

There are three critical geological factors to consider regarding Kathmandu's future risk:

1. Partial Rupture: Seismological data shows that the 2015 rupture did not break all the way to the surface, leaving a significant amount of "unspent" elastic energy in the shallow portion of the fault. This is what geologists call a seismic gap in the central and western regions.
2. Westward Strain Accumulation: Historically, western Nepal has not experienced a major earthquake for over 500 years. This suggests that a "Great Earthquake" (Magnitude 8.5+) is likely in the future, and because Kathmandu sits in the central sector, the seismic waves from such an event would certainly affect the city due to ground motion amplification in the Kathmandu Valley's soft sediment.
3. Tectonic Context: The Indian Plate continues to subduct beneath the Eurasian Plate at a rate of roughly 18-20 mm per year. This constant movement ensures that stress is perpetually rebuilding.

In summary, while we cannot predict when exactly, the geological record and current GPS data indicate that the Kathmandu region remains at high risk for significant future seismic events.