Geological scrum caused Nepal quake

Rescue workers remove debris as they search for victims of earthquake in Bhaktapur near Kathmandu. Photo / Niranjan Shrestha

The big earthquake that rocked Nepal was another violent by-product of an ancient, geological scrum between two giant land masses.

Like an enormous bulldozer blade, India has been constantly colliding with Asia over the past 25 million years, at a speed of several centimetres each year, creating the spectacular Himalayan mountains.

The 7.8 quake's epicentre was 80km northwest of Kathmandu, and had a depth of 11km, considered shallow in geological terms and meaning it had more destructive power.

Such severe quakes are estimated to occur in the region every 75 years.

While a smaller 6.8 quake killed more than 1000 people in 1988, a devastating 8.1 quake in 1934, just under 10km from Mt Everest, killed more than 10,000 people.

A report by Geohazards International said "the 1.5 million people living in the Kathmandu Valley were clearly facing a serious and growing earthquake risk" because of the number of people among flimsily-built buildings.

Scientists believe Kiwis could easily see a quake of the same force here.

"The Alpine Fault, as far as we can tell, could generate quakes of similar size - but mostly, it would be a different style," Victoria University seismologist Dr John Townend said.

"That's because most of the motion in the Alpine Fault is lateral, so one block is sliding past the other horizontally, yet there is still a component of upward motion - that's why we get the Southern Alps."

On the Alpine Fault, 7.8 quakes could occur every 300 or 400 years.