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Anh ngữ đặc biệt: Did Japan’s Early Warning System Work?

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I'm ... with the VOA Special English Technology Report.

A powerful earthquake struck the northeastern coast of Japan at two forty-six p.m. local time on March eleventh. Japan's Meteorological Agency released its first tsunami warnings just three minutes later. The country has one of the best earthquake early warning systems in the world.

There are more than four thousand Seismic Intensity Meters in place throughout Japan to measure earthquake activity. These meters provide information within two minutes of an earthquake happening. Information about the strength and the center of the earthquake can be learned within three minutes.

Costas Synolakis is a tsunami expert with the Department of Civil and Environmental Engineering at the University of Southern California in Los Angeles.

He said Japan is one of the most well-prepared countries on Earth in terms of tsunami warning. They had a warning. I think what went wrong is that they had not anticipated the size of this event.

He says there are two reasons for this. Japan has not had any event anywhere near as big as this one in the last one hundred fifty years. And scientists had not expected such a large earthquake happening off the coast of Japan.

The nine point zero magnitude earthquake was the fourth most powerful earthquake ever recorded worldwide. It was also the worst earthquake ever to hit Japan. The tsunami waves that followed were reported to have reached as high as thirteen meters in some areas.

Costas Synolakis says Japan's concrete sea walls were not built to handle such high waves.

He said: "The concrete seawalls in many places in Japan are about ten meters, that's about thirty-three feet. In Sendai, they were about three meters, that's about ten feet. So that shows you that at least in that area they were not expecting such a sizeable wave."

A tsunami wave can travel as fast as eight hundred kilometers per hour. To get to higher ground people would often have to travel for many kilometers. This can take more time than a fast traveling tsunami will permit. This is especially true in cases like Japan, where the center of the earthquake struck so close to the coastline. The tsunami waves followed almost immediately.

Experts say early warning systems will continue to be limited by these facts until earthquakes and tsunamis can be predicted.

For VOA Special English I'm ...

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