Distant quakes may be related

Editorial, Normal


THE frequency of earthquakes in the Asia-Pacific region in recent weeks must be seen as a cause for concern by coastal villagers and islanders in the area.
Countries on the “ring of fire” stretching from Southeast Asia to the PNG, Solomon Islands, Vanuatu, Fiji, New Caledonia, Samoa, Fiji, Tonga and New Zealand have been specifically identified as being in the danger zone and must be prepared for likely tsunami strikes caused by more earthquakes.
Some Australian experts were shifting their views to believing that the recent deadly earthquakes were related – although Samoa and Padang in Indonesia are 9,960km apart.
On Sept 30, a tsunami triggered by an earthquake in Samoa destroyed villages, killed 140 people and hospitalised 60. A few hours later, another strong earthquake struck Padang in west Sumatra where hundreds of people are still buried under the rubble.
Then, a series of earthquakes shook Vanuatu (last Thursday), the largest measuring 8.0 on the Richter scale, and the country was lucky that it did not trigger a tsunami. Tonga was moderately shaken on Monday measuring only 5.9 in magnitude. Tsunami alerts there were scaled down later in the day.
The latest earthquake activity has triggered a shift toward the belief that earthquakes separated by long distances could be related.
The Australian newspaper on Tuesday reported University of Queensland’s scientist Huilin Xing as proposing a possible link between the Samoan and Padang earthquakes. This is a challenge to the long-accepted science. The two epicentres were over 9,600km apart.
Dr Huilin said the fast-moving Australian tectonic plate might have set off one quake and then the other, the paper reported.
“From the observations, there were similar correlations of the quakes in the different places,” Dr Huilin said. “For two great earthquakes to occur within hours in such a way, it is abnormal.”
Another seismologist, Dr Phil Cummins, of Geoscience Australia, was asked by the same newspaper if the recent quakes had prompted any change of opinion.
“I guess, I think I’d have to take more seriously the possibility that the seismic waves could help to weaken faults even at large distances,” he said.
About two weeks ago, the same Dr Cummins had said other than the fact that they both occurred on the boundaries of the Australian (tectonic) plate, there was no direct causal link that he knew of.
He said although there was no firm way to prove any causal connections between the earthquakes, he said on Tuesday: “You can’t rule out completely the possibility of a connection, or that seismic waves could weaken faults even at large distances from the epicentre.”
Although it was still difficult to determine whether the earthquake cluster was anything more than “a remarkable coincidence”, he said geologists would be looking at the events of the past fortnight with keen interest.
“It’s certainly quite unusual. I haven’t seen it in my career,” Dr Cummins told The Australian.
“There has been no sequence of earthquakes occurring in such rapid succession in such different locations across the globe,” he said.
Veteran earthquake-watcher Gary Gibson, who said more than a week ago that he was treating quakes thousands of kilometres apart as “coincidence”, said on Monday he was re-evaluating that hypothesis.
“I can no longer keep using the response it’s all a big coincidence, can I?” Dr Gibson, a senior seismologist with the Seismology Research Centre at Environmental Systems and Services Victoria, said.
“But what would the (link) mechanism be? Nobody has come up with a good story,” he told The Australian.
But Australian Earthquake Engineering Society president Kevin McCue continued to reject ideas of any connection between the Pacific and Indonesian quakes.
“It’s just the nature of the beast – you have a cluster of events, then you wait months without one. I don’t deny that I don’t know something. It is possible there’s something more. We don’t know what’s happening down there, really,” he conceded to The Australian, one of Australia’s largest selling national dailies.
While scientists are discussing relativity of the quakes, government authorities and scientists in Australia were warning residents along the eastern coastline from the Far North Queensland to Victoria to take extra precautions whenever there is an earthquake in case of a tsunami. Large billboard signs with paintings of high-rising waves were being used as warnings along parts of the Queensland coastline.
Scientists are encouraging similar awareness signs to go up around the Asia-Pacific region including Papua New Guinea as the frequency of earthquakes is likely to increase and coastal villagers and islanders from PNG to New Zealand are particularly at risk.