EARTHQUAKES
Marking 80 years since the Great Kanto Earthquake of 1923, the Museum of Natural Science in Tokyo is holding an exhibition titled “The Earthquake” from August 1 to October 26. Just how much have earthquake research and disaster prevention advanced in the 80 years since that disaster?
By Tadahiro Ohkoshi – Asia-Pacific Perspectives – November 2003
The Japanese people have long enjoyed the rich blessings offered by the land on which they live, from plentiful supplies of sparkling fresh water and bountiful harvest of rice and other crops, to beautiful mountain scenery and soothing hot springs.
These rich blessings are offset by the disasters, which the land also visits upon its inhabitants. Japan is highly earthquake-prone, accounting for roughly 10% of the world’s earthquakes. Over the centuries there have been numerous earthquakes in Japan on a similar scale to the devastating Great Hanshin-Awaji Earthquake of 1995, and each time the country has suffered a great deal of damage.
The earliest recorded instance of an earthquake in Japan is the Yamato Kawachi Earthquake, which occurred in 416 A.D. during the reign of Emperor Ingyo. Reference is made to this earthquake in one of Japan’s oldest historical documents, the Nihon Shoki (Chronicles of Japan). Since then, there have been over 100 recordings of earthquakes with an estimated magnitude of 7 or above (on the Japanese scale), each one leaving a scene of collapsed houses, fires, and devastation from tsunami tidal waves.
In the Great Kanto Earthquake of September 1, 1923, an earthquake of magnitude 7.9 wreaked havoc across Tokyo and the whole Kanto region. Tokyo and a number of other cities suffered immense fir damage, and a huge tsunami tidal wave assaulted the costal regions. Throughout the country, over 254,000 homes collapsed either totally or partially, while over 447,000 homes were destroyed by fire. This dreadful disaster resulted in approximately 142,000 persons killed or missing – the third largest loss of life due to earthquake in the 20th century.
Since then, Japan has made great advances in earthquakes research. At the time of the Great Kanto Earthquake, there was no clear method of indication for seismic intensity, and seismological observation techniques were still in their infancy. Now, the whole country is equipped with a network of highly sensitive seismographs installed in over 1,000 meteorological stations and research facilities, belonging either to the Meteorological Agency and other data centers by the Satellite Telemeter System, which makes earthquake observations throughout Japan possible in real time. Satellites are also used for a Global Positioning System (GPS), which can carry out precise measurements of the motion of the earth’s crust. Japan is thus equipped with one of the most advanced observation systems in the world.
Japan has also led the world in the development of seismographs to measure tremors. Around 300 tremors - both perceptible and imperceptible – are recorded every day in Japan. These tremors occur not only on land, but also on the sea floor. Japan is surrounded by sea, and observation instruments of earthquakes below the sea are extremely important. Development of a sea floor seismograph began in the 1950s, and automatic observation instruments which can be used for up to a period of a year are currently operation.
Given the seismic activity under the densely- populated Tokai region, Japan has long feared the occurrence of a major earthquake there. Kunihiko Schimazaki of Tokyo University’s Earthquake Research Center asserts, “A massive earthquake in the Tokai region, on a scale similar to that of the Great Kanto Earthquake, is definitely on the cards.” So what precautions have been taken to deal with this very real possibility?
In the Great Hanshin-Awaji Earthquake of 1995 over 90,000 houses collapsed, and over 80% of the approximately 5,500 fatalities died after being trapped under rubble of collapsed buildings. Many of the houses of the time were insufficiently reinforced to withstand an earthquake, and research is now being carried out into enhancing the reinforcement technology of wooden structures as well as high-rise buildings. Areas of investigation for making buildings more earthquake- resistant include new technology for seismic isolation and seismic control. Japan is at the forefront of research in these fields.
It is still impossible to predict exactly when an earthquake might occur, and it is that the nation stays prepared. Japan cannot afford to sit back and wait to be hit by earthquakes, but should confront them boldly and positively. The country’s earthquake research is one step in this direction.