An earthquake measuring 7.6 on the Richter scale struck Nantou County yesterday. This was the strongest earthquake recorded in western Taiwan since the collection of seismological data began. At the moment, the people are most concerned about whether there will be another major earthquake, and if there is, how we should protect ourselves and our property.
Central Taiwan has experienced four major earthquakes before. The first was in 1845 (measuring 6 on the Richter scale and killing 381 people); the second in 1848 (7.1 on the Richter scale, killing some 1,000 people); the third in 1916 (magnitude of 6.4, killing 16 people); and the fourth in 1917 (magnitude of 5.8, killing 54 people).
Judging from seismological data, the region released a vast amount of accumulated energy during yesterday's quake. The possibility of another major earthquake in the near future is rather low. The Chiayi-Tainan region still has a high frequency of earthquake activity.
At the moment, the public should beware of this: the preparation for aftershocks over the next few weeks should be taken seriously. If you find many irregular cracks in your building's structure -- especially in beams, columns and floor studs -- this means the building has suffered internal damage. It may not be able to sustain further damage from aftershocks. Residents should not live in the building until it has been renovated.
Current technology is still incapable of predicting earthquakes. To minimize damage, we can only rely on disaster prevention. First of all, take a good look at the design and construction of your home or office. If it was built in accordance with earthquake resistance standards, the building will suffer some damage during an earthquake but will not collapse. The collapse of the hotel on Pateh Road may have been caused by the unique geography of the Taipei basin. The resonance period in Taipei City was about 1.2 seconds or 0.5 to 0.6 seconds. The resonance period for each story of a building is about 0.1 second. So 12-story or five- to six-story buildings are the most susceptible to earthquake damage.
How can you avoid danger when an earthquake hits? The best thing to do is to quickly find cover under a sturdy object like a beam column or a strong piece of furniture. Use a pillow or a soft cushion to protect your head. Never run out of your house because the shaking -- even in a major earthquake -- usually lasts for 20-30 seconds. You simply do not have enough time to run out of a metropolitan highrise. You also run the risk of being hit by falling objects.
Yeh Yih-hsiung is the director of the Institute of Earth Sciences at the Academia Sinica.
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