Japanese trying to develop system to predict temblors
October 19, 2003
After the host of studies done on earthquakes, scientists have little doubt that plate tectonics are the underlying cause. What remains problematic is figuring out when they’ll strike.
The theory is that the layer under Earth’s outer strata, its crust, is comprised of more than 10 huge movable segments called “plates.” When two or more plates collide, or when one creeps under another, an earthquake occurs.
Countries measure earthquakes differently. Americans use the Richter scale; Japanese use two scales, “Magnitude” and “Shindo.” Magnitude is just slightly lower than the U.S. scale, while the Shindo refers to what people actually feel at a given location; the same quake could be a seven at its epicenter, or point of origin, but 500 miles away register just a 2. The Richter measures an earthquake’s magnitude, or the energy it releases at its epicenter. The shindo scale ranges from 1 to 7, the most severe; a magnitude 9 quake tops the Richter scale.
In Japan, where 20 percent of the world’s earthquakes of Magnitude 6 or above occur, the government has spent millions of dollars searching for ways to predict the temblors — an effort given immediacy by 1995’s Great Kansai-Kobe Earthquake, which struck without warning and claimed an estimated 6,425 lives.
“Knowing” and “foretelling” are two different things, said Kozo Kamada of the Headquarters for Earthquake Research Promotion. It’s known that stress can make people sick, he said, but no one can tell when people will actually become sick because of that stress. In the same way, he said, accumulated stress between tectonic plates causes earthquakes, but nobody yet has been able to determine how to forecast when they’ll happen.
But with so many lives and so much property at stake, scientists continue the search — an undertaking that at times can resemble some of the more bizarre segments of “Animal Kingdom.”
Consider the catfish.
Since 2001, Yoichi Noda and his group at Tokai University in Shimizu, Shizuoka Prefecture, have studied whether the creature’s periodic restlessness is an earthquake predictor.
Noda said many reports have surfaced about animals’ abnormal pre-temblor behavior, known as macroscopic anomalies. None have been substantiated, he said, but the possibility cannot be dismissed.
From 1976 to 1992, for instance, Tokyo’s metropolitan government studied catfish. According to the research, 87 quakes with a magnitude of 3 or higher occurred during those 16 years — and in 27 of the quakes, catfish displayed abnormal behavior up to 10 days before the shaking began.
The research didn’t specify why the fish were edgy, but did speculate that catfish can detect an increase in atmospheric energy levels, a phenomenon believed to occur before an earthquake.
Noda said catfish have sensor cells that feel weak electricity in the water to catch prey. He speculated they might be feeling pre-seismic electromagnetic waves in the atmosphere and potential geomagnetic and geoelectric changes preceding earthquakes.
Using the Tokyo government’s research, Noda’s group constructed a digital monitoring system for some potentially relevant elements, such as temperature, pH and nitrous oxide in the fish’s aquarium, mechanical vibration, electromagnetic pulses with various frequencies and atmospheric electric fields. For good measure, they also kept an eye on the catfish via infrared sensor, video camera and vibration sensors.
However, Noda said, despite having arguably the world’s most closely watched catfish, he could not conclude they’re restless before earthquakes. He still hopes, though, to develop a universally accepted method of testing abnormal behavior in animals before earthquakes.
Meanwhile, another group of Japanese scientists is taking a different approach.
Kokudo Chiriin of Japan’s Geographical Survey Institute uses global-positioning systems. Scientists are checking strains on the crust by measuring changes in distance between observation points. With 1,200 GPS stations all over Japan, they make vector maps for 10 districts showing the whole country.
Tetsuro Imakiire said the latest research shows northern Japan — where earthquakes happen frequently — is shrinking east and west from two to three centimeters per year as a result of the Pacific plates pushing and sliding into the North American Plate, on which northern Japan lies.
On May 26, a magnitude 7.1 earthquake was centered off the coast of Miyagi in Tohoku. However, the local GPS registered no measurable changes before the earthquake — only after.
Very shaky fish story
For thousands of years, the Japanese believed earthquakes were caused by an angry catfish living under the Earth’s crust. When the fish shakes its feelers, they thought, a slight tremble would occur.
But when it moves its strong tail, a big earthquake takes place.
At Kashima Shrine in Ibaraki Prefecture, there’s a stone pillar driven into the earth called Kaname-ishi — or pivot stone. According to tradition, the stone is there to hold down the head of a great catfish, so that it won’t shake.
One day, Tokugawa Mitsukuni (1628-1700), the lord of the Mito, tried to root the stone out to verify the legend. Upon his order, workers dug around the stone, but the next morning, they found that the land had returned.
For seven days and seven nights, the legend says, they dug. Many were injured — and so they gave up. Even today, no one knows how deep the stone goes, for it’s said to hold the seismic fish by the head.
Tatsuo Sekizawa of Kashima studied the fish for many years. Recently, he and his group opened the “Namazu Genki Mura” museum, or Catfish Genki Village, near the Kashima Jingu Shrine. It houses all kinds of catfish goods, including ukiyoe prints (namazu-e), books and crafts.
Sekizawa hopes the museum, which resembles a Japanese living room, can also become a place for people to get together and promote friendship.
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