LIMA: Peru has become the latest country to be shaken by the 'Ring of Fire' – a 40,000-kilometre arc of seismic violence that unleashes earthquakes and volcanoes around the Pacific.

Hundreds of people were killed and several cities were devastated, Peruvian authorities said, after the 7.9-magnitude quake rattled the country late Wednesday local time.

The earthquake just off the coast of Peru "was one of the largest that can be expected anywhere in the world in an average year, and caused extensive damage," said earth scientist David Rothery with the U.K.'s Open University. "This one was caused by the Nazca Plate – the floor of the Pacific Ocean – being dragged below the South American Plate."

Ring of Fire

The epicentre of the quake was 148 km southwest of the capital, Lima, at a depth of 40 km, said the U.S. Geological Survey. A second, 5.9-magnitude shock struck an hour and 20 minutes later, near the same location. The main shock prompted evacuations along the coast because of tsunami fears, but the Pacific Tsunami Warning Centre later lifted its warnings.

The Ring of Fire, as geologists call it, stretches along the western coast of the Americas, across the densely populated island nations of East and Southeast Asia, and through the South Pacific. "Most of the seismic energy released on the Earth is somewhere along the Pacific margin," explained Roger Musson, a seismologist with the British Geological Survey in Edinburgh.

All but one of the last century's largest quakes have occurred somewhere along its path, where great chunks of the Earth's crust – floating on the molten rock of the Earth's core – pull apart or butt up against each other competing for space.

Volcanic explosions

This accumulating tectonic pressure is released through volcanic eruptions when the molten rock is ejected as magma through fissures in the crust, and via earthquakes when the pressure causes the crust to buckle and shift. Most of these seismic events are small or occur under the sea, causing little or no loss of life or damage to property.

But occasionally they generate massive volcanic explosions, earthquakes or landslides. A monster quake off the coast of Sumatra in 2004 – along with the Tsunami is set in motion – killed more than 280,000 people in a half a dozen nations.

While experts agree that the Ring of Fire generates more than 80 per cent of the world's earthquakes, they differ as to how far their impact can travel.

"The earthquake that just happened in Peru is undoubtedly related to an 8.4-magnitude earthquake six years ago," said Musson. A large section of the boundary between the tectonic plates that run along the Peruvian coast – the Nazca under the Pacific and the South American Plate – ruptured, creating pressure further down the fault, he explained.

"Where the earthquake in 2001 left off is where this one started," he said, adding that seismologists predicted at the time that another tremblor would follow within decades. "It just happened a bit sooner than we expected."

Tectonic connections

Musson added that it is very unlikely, however, that the quake on Wednesday would have any direct impact on regions across the Rim or in North America, pointing out that the many tectonic plates connecting to the Pacific "are not exactly part of the same picture."

Pacal Bernard, a seismologist at the Institute of Earth Physics in Paris, France, said distant rumblings were indeed possible. "A big quake such as the one that occurred in Peru can disturb neighbouring plates" in the Ring of Fire, he said. "Statistically, we can expect several small earthquakes elsewhere of a magnitude of six or less."

But the fact that several quakes often occur in a short space of time does not necessarily mean they have a direct impact on each other. "Earthquakes do tend to happen in clusters but they aren't triggered by one another," commented Gary Gibson, professor of seismology at RMIT University in Melbourne, Australia.