Accurate quake forecast still not possible: Experts

June 4th, 2008 - 6:43 pm ICT by IANS  

Beijing, June 4 (Xinhua) The earthquake on May 12 in China’s southwest took less than two minutes to kill some 70,000 people and injure many more, mostly in Sichuan province. Shock turned to grief and then to anger as people began to look for someone to blame.

The target of the anger is China Earthquake Administration (CEA). The chief mission of the CEA’s Institute of Earthquake Science is to make short and medium term earthquake predictions.

An accurate forecast could have saved many lives, and many Chinese wonder why, after almost 30 years in operation, the CEA institute failed to provide one.

Some conspiracy theories were floated that there were predictions, which were suppressed because of the upcoming Olympic Games.

CEA experts spoke out to the media, expressing sorrow for the losses but defending their work and denying a cover-up.

Short-term quake forecasts — meaning days or hours, with an accurate description of area and magnitude — are almost impossible with current technology, the CEA experts said.

“We are unable to penetrate deep under the earth. The conception of an earthquake is very complicated, and the recurrence of big earthquakes in a given region takes a long time,” said China Earthquake Networks Center (CENC)’s deputy director Zhang Xiaodong.

Accurate earthquake predictions remain a problem for scientists around the world, including China, which has a long historical record of quakes.

What is considered to be the first successful quake forecast was made in China more than three decades ago, involving a 7.3-magnitude quake in Haicheng, Liaoning province in the northeast.

The prediction was based chiefly on a spike in minor quakes in the region.

But the same method failed to predict a huge quake the following year in Tangshan, near Beijing, which killed some 240,000 people.

In the case of the May 12 quake, there was no such foreshadowing surge in small quakes at the epicentre which was located at Wenchuan county, said Che Shi, deputy chief of the CEA’s monitoring and prediction division.

The minor quakes were all less than 1.0 on the Richter scale. And no prediction was made.

Che said that the office had not received any report of tremors in the county or accounts of abnormal animal behaviour prior to the quake in the area.

But media reports have said that toad swarms were seen in the streets in the region not long before the disaster.

“The division is responsible for managing such information. If reports reached us, they would have been properly processed,” Che said.

With the Internet, it is easy to find reports and videos on anomalies in animal behaviour and inexplicable natural phenomena, such as the sudden drainage of a water body, before an earthquake.

Such phenomena might have a connection with a quake, but not necessarily, an expert told Xinhua.

These events could also be caused by climate change or a natural process that humans do not yet understand. CEA received such reports almost every day from around the country, one agency source said.

Short-term forecasts should help people take precautions against an earthquake. But living in a tent or in the open air, especially if the weather was bad, could cause serious health problems and even deaths, especially if the forecast was not specific and the efforts dragged on for weeks or months, experts said.

The direct and indirect costs might be huge, perhaps even comparable to the damage caused by a quake that hit unprepared people, they said.

The recent prediction of possible strong aftershocks in May 19-20 in the Wenchuan and neighbouring areas was just such a trying moment. “We hesitated for hours,” recalled a CEA senior researcher who was involved in the decision-making.

The alarm was finally sounded experts, but it turned out to be false.

But the public understood, and it exacted little extra cost on the affected communities, which were already on alert for any trembling underfoot.

Earthquake scientists base their studies on scientific evidence and reasoning. They would propose issuing an official forecast only when they believe the evidence warrant it.

Going by experts’ account, in the Wenchuan case, the absence of an alarm was not dereliction of duty.

“I couldn’t hold back tears in the office,” said a scientist who asked not to be identified. “At the sight of the appalling scenes, especially the suffering of children, who wouldn’t be disturbed?”

Seismologists might be sadder than others, perhaps, wishing that their forecasting ability were more advanced.

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