The Ocean Hemisphere network Project - "New eyes to see the interior of the Earth" - started in April of 1996 under a grant from the Ministry of Education, Science, Sports and Culture, of Japan. This is a five-year project, under which the Principal Investigator, Y. Fukao ( ERI, Univ. Tokyo ), and many other scientists aim to investigate the structure and dynamics of the Earth's deep interior by constructing a new network of various types of geophysical observatories in the western Pacific region and other nearby regions. Because of various practical constrants, the density of geophysical observatories in this important region has heretofore been sparse. By installing instruments at a spacing of approximately 10 degrees ( 1,000 km ), we hope to significantly improve the resolution and accuracy of seismic, geomagnetic, and geodetic investigations. The overall plans for the Ocean Hemisphere Network are as follows. In our target hemisphere, centered on the Pacific, more than 90% of the surface is covered by the ocean, which is the major obstacle to good observational coverage. One of our largest efforts will therefore be to establish observation sites on a number of islands in the Pacific. However, the region that can be covered by observations on islands is limited. Seafloor observatories are needed to achieve a complete coverage, and one of the other main components of our project is therefore a technological development to enable us to carry out a long term observations at the bottom of the deep oceans. Using the data obtained from the OHP Network together with other data, research will be performed to investigate.

( 1 ) The possible presence in the lower mantle large-scale hot or cold material and / or chemically different material
( 2 ) Heterogeneity in the core-mantle boundary region that may be strongly related to variations in the geomagnetic field and in the Earth's rotation
( 3 ) Surface motion ( plate motion ) and surface deformation ( intraplate deformation ) due to mantle convection
( 4 ) Geodynamic processes on a global scale, from the Earth's center to the surface

The project is being carried out by four research groups. Group I is led by I. Yamada and the deputy leader is M. Kimata ( both Faculty of Science, Nagoya Univ.). This group is installing and operating broad-band seismic, geomagnetic and GPS networks on the Pacific islands. Group II is led by K. Suyehiro and the deputy leader is A. Taira ( both ORI,Univ. Tokyo ). This group is conducting offshore experiments and downhole observations. Group III is led by Y. Hamano ( Faculty of Science, Univ. Tokyo ) and the deputy leader is T. Kanazawa ( ERI, Univ. Tokyo ). This group is developing new instruments and making new observations. Group IV is led by Y. Fukao ( ERI, Univ. Tokyo ) and the deputy leader is R. Geller ( Faculty of Science, Univ. Tokyo ). This group is operating the data center to edit, distribute, and analyze the data from the Ocean Hemisphere Network. This group is also developing new modeling and analysis techniques. The details of each group's activities are discussed below.