J-array

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In 1987, the International Union of Geodesy and Geophysics (IUGG) formed a committee for Study of the Earth's Deep Interior (SEDI). Its main aim is in studying the Earth' core and the lower mantle, regarding it as an important part of earth science. Scientists around the world began researches on the Earth's core. This interest in the Earth' core also rose in Japan, and in 1990, project "Earth's Core" received the Grants-Aid for Scientific Research on Priority Areas from the Ministry of Education, Science, Sports and Culture. "J-Array" was part of the project."J-Array" can be considered as a giant telescope aimed at the Earth's interior. The sensors for this telescope are short-period seismometers. This project aims to pick up signals of micro-earthquakes from background noise by amplifying it by array observation. The final object is to define the fine structures of the Earth' interior to understand the motions and history of the Earth' interior by catching the seismic waves (P and S … More waves) that were reflected and refracted by various surfaces in the Earth.Under this grant-in-aid, further recordings and analyzes were continued for increasing the database for large earthquakes and earthquakes occurring in different regions. The "J-Array" project should take into consideration the possible applications of the database and future prospects. A compilation of the seismic waveform data for the major earthquakes was published. This book most certainly plays an important role in further studies and education. A CD-ROM containing the seismic database (SAC format) was also published. It will be a big contribution from Japan to earth science in the world.Although the "J-Array" is large, it is still small compared to the size of the Earth. Therefore, the portion of the Earth's interior that can be observed by it is also limited. To overcome this problem, it is necessary to cooperate with other countries. Many seismic observation networks exist in the world today such as the network in California with 700 observation points, the North China network with 100 points, the network of Taiwan with 60 points, the Graefenburg Array of Germany, and the Warramunga Array of Australia. By collaborating with these networks, it will be possible to observe thee Earth's interior from all angles. These collaboration will be conducted in the next "New J-array Project". Less