Anecdotal evidence collected from witnesses in the remote islands of Nias and Simeulue, which were close to the epicentre of Monday's 8.7-maginitude quake, points to substantial change on shorelines around the islands.

In some areas, the land has tilted, exposing large tracts of beach that were once below the water line and thrusting coral reefs up into the air, while dipping other low lying coastal areas into the sea.

Photos shot by Brian Williams, an Australian running a surf camp on Simuelue, show a wide strip of white sand in Simuelue's Gusong Bay, which people familiar with the area say was not there before.

"I was there recently. The beach used to be three metres (yards) wide, now it's 30 metres wide and reefs that were underwater are now above water," Kirk Wilcox of the surfing goods firm Quicksilver, said.

"The same lifting occurred on the top part of Simeulue island after the first earthquake on December 26, 2004, while the lower part of Simeulue dropped."

The December quake, now measured at 9.3 on the Richter scale, caused major upheaval in the region as two continental plates that collide on a fault line close to Nias and Simeulue crunched against each other.

Tsunamis unleashed by the quake also caused enormous damage to the region's coastlines, killing in excess of 270,000 people.

Eyewitnesses say the latest quake also triggered a moderate tsunami, three metres in height, which caused a small amount of damage on Simeulue and the Sumatra coast area of Singkil, where it surged several hundred metres inland.