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| A line of volcanoes is the most visible sign of Indonesia's seismic activity [EPA] |
Brutal and deadly as they often are, earthquakes are a fact of life for Indonesia.
Indeed the country owes its very shape and the extraordinary fertility of much of its land to the same seismic forces that cause earthquakes.
Straddling the so-called Ring of Fire that encircles the Pacific, the islands of the Indonesian archipelago closely follow the border between some of the most active tectonic plates that make up the Earth's crust.
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| The Ring of Fire around the Pacific is the most seismically active region on Earth |
It is the collision between these plates, floating on a subterranean pool of molten rock or magma, that has shaped and continues to shape the country, most visibly in the string of active volcanoes that line the archipelago.
From time to time, those volcanoes erupt, often with spectacular and sometimes deadly results.
But years of study and monitoring have made predicting eruptions more accurate and helped minimise casualties.
Earthquakes, however, remain far harder to predict and often cause far greater loss of life.
The deadliest quake of recent years was the December 26, 2004 event off the coast of Sumatra that spawned a region-wide tsunami killing more than 240,000 people across Asia – 170,000 in Indonesia alone.
Pressure released
That undersea quake had a magnitude of 9.3, one of the most powerful in recent memory, and has been followed by a series of unusually strong quakes in the same region.
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| Recent quakes in Samoa and Sumatra both hit at the junction of active tectonic plates |
Clive Collins, a senior seismologist with Geoscience Australia, says it is likely the increase in seismic activity can be traced back to the forces unleashed by the giant 2004 earthquake.
"We don't know exactly how often extremely large earthquakes do occur, but because of the 2004 event it has obviously modified some of the stresses and pressures in that region and they're being released now in these larger earthquakes," he told Al Jazeera.
Possibly there may be more to come, Collins said, but the understanding of where and when those may occur is extremely limited.
"The plate margins tend to slip within restricted regions, so you get a large earthquake and then you might get the adjacent region slipping and breaking causing another large earthquake," he said.
"Whether they all unzip at the same time though is the question."
However, Collins said he doubted that the recent spate of powerful quakes showed the region was building up to a cataclysmic event, as some have suggested.
History has shown, he said, that seismic activity in the so-called subduction zone off Sumatra - where one plate slips beneath another- has occurred in "fits and starts".
"If these stresses are being released in these large earthquakes, that takes the pressure off along that whole margin - it's unlikely that the whole of that subduction zone will link up and move all at once."
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