This graphic provided by the National Oceanic and Atmospheric Administration (NOAA) shows tsunami travel times following an earthquake with a magnitude of 8.0 rocked the island nation of Samoa, causing a tsunami.
Credit: NOAA/AFP
SYDNEY: Following seismic activity in Vanuatu, researchers have suggested that the motion of the Australian tectonic plate may be responsible for recent earthquakes in both Indonesia and the South Pacific.
They argue that the earthquake and tsunami, that took place in Samoa just over a week ago, may have a common cause to a quake in Sumatra and the three quakes near Vanuatu.
This is despite the fact that Samoa and Sumatra are more than 6,000 km apart.
"Based on these observations, it's rare to have so many large earthquakes occurring in this way in such a short period of time," said team-leader Huilin Xing, a geoscientist with the University of Queensland, in Brisbane, Australia.
Sudden slip
The first earthquake on September 29, near Samoa, measured 8.0 on the Richter scale, the second, which occurred only 16 hours later in Sumatra, was a magnitude 7.6 quake. On Thursday, three more quakes occurred around Vanuatu reaching 7.8, 7.7 and 7.3.
An earthquake develops when there is a sudden slip between the tectonic plates that cover the Earth's crust. These plates are constantly moving, but friction can cause them to get stuck at their edges. When the stress on the plate overcomes the friction, there is an earthquake, releasing the pent-up energy in seismic waves.
The tectonic plate that Australia sits on borders the Indian, Eurasian, Philippine and Pacific plates. Given all recent seismic events occurred around the Australian plate boundary, researchers suggest the motion of the Australian plate may be responsible.
High-risk zone
Using computer simulations, Xing's team studied the area around Sumatra as a high-risk zone for seismic and tsunami activity. Since previous earthquakes have been predicted using this method, Xing claims that simulating fault systems can provide critical information to monitor earthquakes.
"The dream for scientists is to predict the earthquakes as accurately as they can the weather," he said.
However, Kevin McCue president of the Australian Earthquake Engineering Society, in Canberra, doesn't agree that the concurrent occurrence of the quakes is abnormal.
"In my opinion the earthquakes of the Southwest Pacific – Samoa last week and Vanuatu this week – are causally related," McCue said. But he believes that the Sumatra earthquakes were too distant to be linked to them and are more probably related to the 2004 Boxing Day earthquake that caused a major tsunami in southeast Asia.
Adam Pascale head of seismology at Environmental Systems and Services an advanced technology and engineering company, based in Victoria, also believes the earthquakes may not be related to one another.
"In any randomly distributed population of events, clusters become apparent over time. The current levels of activity are unusual but not uncommon," he said. "Events of this frequency and magnitude, and worse, have occurred in the past and will continue to do so for millennia."
Key is being prepared
Predicting when quakes are going to strike with any accuracy is problematic, he said. Instead, he argued that preparation is the key: "Public education about earthquake and tsunami safety will prevent loss of life in the short term," while improving building standards is a more long-term solution.
The Samoan earthquake led to a tsunami which struck Samoa, American Samoa and Tonga killing 170 people. The quake that struck the Indonesian island of Sumatra killed over 1,000 people mostly through the effect of collapsed buildings.
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