Earthquake escalation?

The 6.4-magnitude Taiwan earthquake that hit on Thursday – on the heels of quakes in Haiti and Chile – raised concern of an accelerating trend. But the statistics say otherwise.

Christian Science Monitor, March 4, 2010

Taipei, Taiwan -- The 6.4-magnitude Taiwan earthquake that hit Thursday on the heels of massive quakes in Haiti and Chile, has some worrying about a spike in seismic activity.

But there's no geological connection between those quakes, and nothing unusual in the number of recent big quakes, says Kuo Kai-wen, director of the Seismology Center of Taiwan's Central Weather Bureau.

"Because Haiti just happened, everyone's paying more attention to earthquakes," says Mr. Kuo. "But the activity is normal – it's not so scary."

IN PICTURES: Images from the Taiwan earthquake

About 64 injuries have been reported from Taiwan's quake, which hit about 250 miles south of Taipei at 8:18 am local time and was followed by several aftershocks. But it triggered power outages, halted high-speed rail service, and caused panic as people ran out of schools and homes.

Kuo says the Taiwan, Chile, and Haiti quakes involved different tectonic plates. Globally, he says, there's an average of one magnitude 8 or higher earthquake per year, some 17 magnitude 7 or higher quakes, and 170 to 180 of magnitude 6 or larger.

So far this year there's only been one quake higher than 8 – Chile's fearsome, 8.8 magnitude temblor. Last year there were 16 magnitude 7 or higher quakes, right at the average. And so far this year there have been three magnitude 7 or higher quakes, including Haiti's.

"From a global view, that's not especially a lot," says Kuo.

Taiwan is frequently rocked by quakes, experiencing one of magnitude 7 or higher every five years and a quake of magnitude 6 or higher every 100 days. "We've only had one like this so far this year, so that's still normal," says Kuo.

Kuo's numbers were from the Richter or "local" magnitude scale, which is slightly different from the "moment magnitude" scale used by the US Geological Survey.

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