While Taiwan was absorbed with Christmas festivities, an earthquake measuring 9.0 struck off the west coast of Sumatra. The quake generated tsunamis that led to thousands of deaths and injuries. We who have experienced the 921 Earthquake feel undefinable shock at hearing news of another powerful earthquake and the effect of the tsunamis. We hope that Indonesia, Thailand, Bangladesh, Sri Lanka and Malaysia will soon recover from the tragic loss of life caused by the earthquake and tsunamis.
In the face of this disaster, we should take special note of the effect of tsunamis. Tsunamis are caused by a large-scale displacement of the sea floor, usually following large earthquakes, major submarine slides or volcanic explosions. When a tsunami hits coastal areas, it causes massive damage to the earth's surface.
Tsunamis often happen when the epicenter of an earthquake is less than 50km deep, so that the massive submarine movement in the earth's crust generates huge pressure on the ocean, which is transmitted outward in a wave. Few countries in South Asia escaped the effects of this tsunami, an indication of the force generated by this earthquake.
When the tsunami reaches coastal shallows, it can rise to 30m in height, and the force with which it hits the coast is enormous. The tsunami that hit northern Papua New Guinea in July 17, 1998, left over 8,000 people dead or missing, completely obliterating a coastal village.
Taiwanese are not too concerned about tsunamis for they have little experience of their effects. But according to historical records, there are six instances of such phenomena occurring here. In April and May of 1781, the chapter on unusual phenomena in the Miscellany section of the Records of Taiwan County, with support from two other texts, records an instance that took place in the Chiatung region near Pingtung. The record tells of a day of extraordinarily good weather when the ocean suddenly roared like thunder and, in a rush that seemed to suck the air away, a wave 30m high rose up, inundating nearby villages.
The Records of Taiwan County also list a similar incident that affected the Luermen area near Tainan.
The most recent of such incidents took place on Dec. 18, 1867, off Keelung. The record tells of coastal mountains tilting, the earth splitting open and the whole island shaking. Many houses collapsed in Keelung and hundreds of people died. The water drained out of Keelung harbor so that the sea bed was revealed, then suddenly returned in a huge wave. Boats were washed into the city center and there was much damage. In many locations the ground and the mountains split open and water poured from the fissures.
This last incident was most likely a tsunami and is a strong indication that tsunamis have originated off Taiwan's coast.
We must therefore realize the potential threat tsunamis pose to Taiwan. This is especially so off the eastern coast, where there is a small but significant population. We should take this opportunity to learn how to minimize the destruction caused and ways of dealing with it should it occur.
What I suggest is that the government departments involved in urban planning, coastal engineering and public works should incorporate the potential devastation of a tsunami into their considerations. Disaster prevention and rescue facilities established by the public and private sectors should avoid areas which tsunamis might hit in order to reduce the level of damage.