Background: Peru earthquakes

Peru, like much of the west coast of North and South America, lies above an area of intense seismic activity and is no stranger to earthquakes.

The nearby Nazca tectonic plate, which lies under the Pacific Ocean, is forced underneath the South American continental plate at a rate of about 4 cm a year.

That may not sound a lot but it is enough to put huge strain on the earth's crust. The pressures are periodically released through earthquakes.

To the south of the site of today's earthquake, the two tectonic plates meet a third one, the Antarctic plate. It is at this three-way junction that the most powerful earthquake ever recorded anywhere occurred.

The Great Chilean earthquake, also known as the Valdivian earthquake, happened on May 22 1960, and measured 9.5 on the Richter scale. It was felt as far away as Alaska and Japan and claimed up to 6,000 lives.

The death toll would have been much higher had many people not been at church - often the strongest building in any town - when the earthquake occurred. A resulting tsunami devastated the Hawaiian island of Hilo.

Peru has experienced more than a dozen earthquakes which caused fatalities in the past century, the most deadly being that of May 31 1970, which killed up to 70,000 people and destroyed 200,000 homes and buildings. The 7.9 earthquake and resulting landslide was the fourth most deadly of the 20th century and the worst natural disaster ever recorded in the country.

The second deadliest recorded earthquake in Peru struck Lima in October 1746, almost destroying the city.