In March, a magnitude 9.0 undersea megathrust earthquake, now known as the Great East Japan Earthquake, hit Japan. One of the five most powerful earthquakes in the world overall since modern record-keeping began, the quake created a tsunami, killed more than 15,000, destroyed billions worth of infrastructure and caused a number of nuclear accidents.

On Sunday, a strong 6.4-magnitude earthquake struck near the coast of Indonesia's Papua province. There were no immediate reports of damage or tsunami warnings issued.

Aside from Indonesia, during the past week moderate to strong earthquakes have hit Japan; nations in the Pacific like Fiji; Latin American countries like Chile and Argentina; Alaska in the United States; and even Antartica.

The Irish Weather Online reported that 2011 is on target to record the largest number of earthquakes in a single year for at least 12 years.

According to the U.S. Geological Survey, earthquakes with magnitude of at least 5.5 that have hit during the past week include:

* June 20. A strong 6.5 magnitude earthquake struck the Antofagasta region of Chile Monday afternoon.

* June 21. A 6.1 magnitude quake hit Santa Cruz Islands

* June 22. A magnitude 6.7 quake struck off the coast of Honshu, Japan, prompting authorities to issue a tsunami alert for the northeast of the country. A series of large tremors measuring greater than 5 have been recorded since the quake.

* June 23. A 7.2 magnitude earthquake hit the sparsely populated Fox Islands region of the Aleutian Islands in Alaska, USA. The quake hit just two days after a 5.1 magnitude earthquake hit the Rat Islands region.

* June 24. A 6.2 magnitude earthquake struck The Solomon Islands in the south-western Pacific Ocean. It was the third strong earthquake to hit the region during the week.

* June 24. A 6.3 quake off the Santa Cruz Islands struck.

* June 24. A 5.6 quake off Hokkaido, Japan Region, struck.

* June 25. A 5.7 magnitude quake off the south of the Fiji Islands struck.

* June 26. A strong 6.4-magnitude earthquake struck near the coast of Indonesia's Papua province. The quake struck at a depth of 36 kilometers, 161 km from Enarotali, at 9:16 p.m.

According to Indonesia's Meteorology and Geophysics Agency, the epicentre from last Sunday's quake was on land 32 km southeast of Waren, a town on the northern coast of Papua island. The 6.4 magnitude quake was followed by two strong aftershocks, the first of magnitude 5.3, the second of magnitude 5.5, the agency said. The quake did not or does not generate a tsunami, according to the Indonesian agency. However, according to The Associated Press, the quake caused panic among residents.

Earthquakes and the tsunamis that they generate usually cause panic in Indonesia. In 2004, the 9.3 magnitude quake off the west coast of Sumatra, Indonesia created a tsunami with waves of up to 30 meters, which killed an estimated more than 150,000 people in northern Sumatra.

The Richter Scale

The Richter magnitude scale was developed in 1935 by Charles F. Richter of the California Institute of Technology as a mathematical device to compare the size of earthquakes. The magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs.

Generally, for locations near the epicentre, these effects may be observed:

Magnitude Description Earthquake effects

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5.0-5.9 Moderate Can cause major damage to poorly constructed buildings over small regions. At most slight damage to well- designed buildings.

6.0-6.9 Strong Can be destructive in areas up to about 160 kilometres across in populated areas. Occurrence is 120 per year

7.0-7.9 Major Can cause serious damage over larger areas. Occurrence is 18 per year

8.0-8.9 Great Can cause serious damage in areas several hundred kilometres across. Occurrence is 1 per year.

9.0-9.9 Great Devastating in areas several thousand kilometres across. Occurrence is 1 per 20 years 10.0+ Massive Never recorded, widespread devastation across very large areas; This has never been recorded.

"Ring of Fire"

Indonesia and the other nations affected by the recent quakes sit on the Pacific "Ring of Fire," where the meeting of continental plates causes high seismic activity, and is frequently hit by earthquakes. The Ring of Fire is an arc stretching from New Zealand, along the eastern edge of Asia, north across the Aleutian Islands of Alaska, and south along the coast of North and South America. Large numbers of earthquakes and volcanic eruptions occur in the Ring of Fire. The Ring of Fire is composed over 75% of the world's active and dormant volcanoes.

Australia?

The Ring of Fire excludes Australia because the continent lies in the center of its tectonic plate.

According to Geoscience Australia, although Australia is not on the edge of a plate, the continent experiences earthquakes because the Indo-Australian plate is being pushed north and is colliding with the Eurasian, Philippine and Pacific plates. This causes the build up of stress in the interior of the Indo-Australian plate which is released during earthquakes.

In Australia, earthquakes above magnitude 5.5, such as the 5.6 magnitude event in Newcastle in 1989, occur on average every two years. About every five years there is a potentially disastrous earthquake of magnitude 6.0 or more. Australia's largest recorded earthquake was in 1941 at Meeberrie in Western Australia with an estimated magnitude of 7.2 but it occurred in a remote, largely unpopulated area.