Oct 27, 2010 07:52 GMT  ·  By
Image showing the location of the new earthquake's epicenter, and subsequent aftershocks
   Image showing the location of the new earthquake's epicenter, and subsequent aftershocks

Experts announce that a massive earthquake struck off the coast of Indonesia on October 25, at a depth of about 20.6 kilometers (12.8 miles) below the ocean crust.

The magnitude 7.7 tremor occurred at 9:42 pm local time (14:42 UTC) on Monday, and generated a 10-foot (3.3-meter) tsunami that struck Pagai Island. The area is only accessible by boat.

Rough seas in the aftermath of the disaster made it difficult for rescue workers to reach the area, and conduct assessments on the damage that the tremor caused.

A day after the earthquake took place, early news reports indicated that as many as 100 people may have lost their lives during the tremor, with an additional 500 being declared missing from their homes.

This rendition of the affected area contains data from the NASA Earth Observatory, the General Bathymetric Chart of the Oceans, the Shuttle Radar Topography Mission, the USGS Earthquake Hazard Program, and the Sumatran Plate Boundary Project.

The map shows the epicenter of the original tremor (red star), as well as the most important aftershocks that struck the region on October 25 and October 26.

The ocean, depicted here in shades of blue, is also marked with black lines to evidence areas where tectonic plates in this region of the Indian Ocean collide with each other.

The earthquake was most likely produced by interactions between the Australia Plate and the Sunda Plate, with the former sliding under the latter. Friction between such plates often causes tremors.

These conclusions came from experts at the US Geological Survey (USGS), who also explain that the Australia Plate is moving north-northeast at a speed of about 57 to 69 millimeters per year.

Records appear to indicate that this quake was only the last in a series of ruptures that took place in this intricate fault line system.

A similar disaster struck the area on December 26, 2004, when a 9.1-magnitude earthquake was triggered some 800 kilometers (500 miles) north of the new epicenter.

That quake triggered a devastating tsunami, which affected numerous countries in the area, produced massive damage, and caused the deaths of more than 200,000 people.

One of the reasons why Indonesia experiences such a high degree of seismic activity is because the country is located in the Pacific Ring of Fire, a cluster of volcanoes and fault lines that surrounds the world's largest ocean.