(Adds detail on refineries, fishing boats, Hawaii alert, context on recent tremors)
By Anthony Esposito
SANTIAGO, April 2 (Reuters) - Thousands of people who evacuated Chile's low-lying coastal areas returned home on Wednesday morning after authorities called off a tsunami alarm as damage from a massive overnight earthquake seemed mostly limited.
The earthquake, with a magnitude of 8.2, struck off the coast of northern Chile near the copper exporting port of Iquique on Tuesday evening, killing six and triggering a tsunami that pounded the shore with 2-meter (7-foot) waves.
Mines in Chile, the world's No. 1 copper producer, mostly said they were functioning normally, and oil refineries said they were normalizing operations.
The country's president, Michelle Bachelet, declared parts of Chile's north a disaster zone, promising troops and police reinforcements to maintain order while damage was repaired after landslides blocked roads.
Bachelet was scheduled to visit the affected areas later Wednesday as authorities evaluate the full extent of damage.
Local television showed images of smaller fishing vessels damaged and overturned in at least one northern port.
Thousands of miles away in Hawaii, the Pacific Tsunami Warning Center cautioned residents that possible sea level changes and strong currents could pose a danger to swimmers and boaters.
PREPARING FOR THE BIG ONE
Chileans live in one of the most earthquake-prone areas of the world, and in particular, residents in the area where Tuesday's quake hit have been expecting 'the big one' for many years.
The Nazca and South American tectonic plates rub up against each other just off the coast of Iquique, where a 'seismic gap' has been building up.
An unusually large number of tremors in the area in recent weeks had led authorities to reinforce emergency procedures, while residents had been buying emergency rations, and preparing for an eventual evacuation.
"The government of Chile has been working hard to improve the awareness of people living along the coast to the threat from tsunamis and on what to do if one is approaching," said Steven Godby, an expert in disaster management at Nottingham Trent University in Nottingham, England.
"Several tsunami drills have taken place since the (earthquake and) tsunami that killed an estimated 500 plus Chileans in February 2010, and recent earthquakes in the region have helped to keep the threat firmly in people's minds," he added.
Over 900,000 people were evacuated from the coastline along Chile on Tuesday, the government's emergency office said, in a move that media said took place in a largely orderly fashion. (Additional reporting by Rosalba O'Brien; Editing by Jeffrey Benkoe and Chizu Nomiyama)