6-9）Ocean Hemisphere Research Center

 

Ocean Hemisphere Research Center (OHRC) is the newest component of Earthquake Research Institute. This center carried out 6-year project "Ocean Hemisphere Network" to build a global multidisciplinary geophysical observation network in the Pacific hemisphere consisting of seismic, geoelectromagnetic, and geodetic observations, and further operate to understand the structure and dynamics of the Earth’s deep interior. Studies are intensively made by using the observation network, not only by the staffs of this center but also scientists from other institutes and departments both of University of Tokyo and of other Universities. This center works as a data center that distributes the data in the international science community and makes as complete a database as possible by data exchanges with other geophysical networks.

In recent years, dynamic nature of the Earth's interior is recognized as a result of various interactions. It is necessary to have an observation network of global scale in order to totally understand the physical phenomena on and within the Earth. From this view point, ocean, which covers about 70% of the Earth's surface, can be regarded as a window to look into the Earth's interior without disturbance by complicated geological noises of the continental crust. At the same time, ocean, especially the Pacific that is the largest on the globe, prevents us from building geophysical observation stations. In fact there have been few attempts to construct a geophysical network in the Pacific due to various kinds of difficulties. In "Ocean Hemisphere Network," largest efforts have been paid to build a well-spread seismic, geomagnetic and geodetic networks in the Pacific to investigate the structure and dynamics of the mantle and the core and to reveal the physics of the Earth's activity.

There are four major activities of this center as follows.

(1) Observation and maintenance of the seismic, geomagnetic and geodetic networks. Since most of long-term observation stations are built on islands in the Pacific, their maintenance requires a collaboration between institutions. A temporal array study, either on land or on ocean bottom, will be done to support the network observations.

(2) Development of new instruments and sensors. It is obvious that stations on islands are not sufficient to build a network of ideal configuration. Long-term seafloor stations for seismic and magnetic measurements are going to be developed to overcome this problem. A borehole seismic sensor will be developed to make a high-quality seismic observation on seafloor.

(3) Data analysis and study on the structure and dynamics of the Earth's interior.

(4) Data distribution and exchange. Data center pays a large effort to distribute data to as many scientists as possible not only in Japan but also in other countries, so as to make a sufficient contribution to the international scientific community.

Fig. 1. (Top) Ocean hemisphere seismic observation network. (Middle) Ocean hemisphere geomagnetic and geoelectric observation network. (Bottom) Ocean hemisphere geodetic observation network.

                                                       

 

Site name	Code	Geographic Lat．	Geographic Lon．	Associ． Inst．	Operation
Huancayo	HUA	-12．06	-75．20	IGP	1997/07-
Kiritimati	KTM	2．05	-157．50	NASDA	1997/08-
Ponape	PON	7．00	158．33	PATS	1997/03-
Changchun	CHC	43．90	125．30	China Seismological Buleau	1998/07-
Tonga	TNG	-21．10	-175．10	MLSNR ． Tonga	1999/09-
Marcus	MRQ	24．18	153．58	JMA	2000/09-
Muntinlupa	MNT	14．40	121．0	NAMRIA	2000/12-
Majuro	MJR	7．10	171．20	Island Eco．	2001/03-
Kanchanaburi	TLD	14．00	98．50	Mahidol University	2002/03-