15:30 〜 16:30
[G02-P-04] Establishment of the new Japan Gravity Standardization Network (JGSN) 2016
Geospatial Information Authority of Japan (GSI) has released a new JGSN2016 in March 2017 for the first time in 40 years using the latest land gravity data over Japan measured by highly accurate gravimeters.
Before that, JGSN75, which is established by GSI in 1976, has been used as a gravity standard in Japan. It is the gravity network decided by only relative gravity measurements based on IGSN71 and has been widely utilized in both social and scientific fields such as determining domestic altitude standards, correcting the results of leveling surveys, exploring underground structures reflected hidden active faults and calibration of measuring instruments. On the other hand, due to mainly active crustal movements, the gravity values vary both spatially and temporally in Japan according to the redistribution of the underground mass. In fact, the difference between the gravity value of JGSN75 and current one reached 0.1mGal at maximum. In addition, along with the recent advancement of gravity measuring instruments and technologies, more accurate gravity standard had been required.
JGSN2016 was conducted by both absolute and relative gravity data carried out by GSI between 2002 and 2016, including gravitational changes accompanying big earthquakes such as 2011 Tohoku earthquake. Especially, in order to obtain absolute gravity values which are consistent with international standards, we calibrated our FG5 absolute gravimeter once a year to the one owned by National Institute of Advanced Industrial Science and Technology (AIST)which participated in the international comparative observation supported by BIPM so that we could. Furthermore, we
established 33 absolute gravity points with precise position coordinates and reviewed and unified analysis parameters such as tidal correction as new attempts. With this kind of ingenuity, we realize a highly accurate and reliable gravity network covering all over Japan.
Before that, JGSN75, which is established by GSI in 1976, has been used as a gravity standard in Japan. It is the gravity network decided by only relative gravity measurements based on IGSN71 and has been widely utilized in both social and scientific fields such as determining domestic altitude standards, correcting the results of leveling surveys, exploring underground structures reflected hidden active faults and calibration of measuring instruments. On the other hand, due to mainly active crustal movements, the gravity values vary both spatially and temporally in Japan according to the redistribution of the underground mass. In fact, the difference between the gravity value of JGSN75 and current one reached 0.1mGal at maximum. In addition, along with the recent advancement of gravity measuring instruments and technologies, more accurate gravity standard had been required.
JGSN2016 was conducted by both absolute and relative gravity data carried out by GSI between 2002 and 2016, including gravitational changes accompanying big earthquakes such as 2011 Tohoku earthquake. Especially, in order to obtain absolute gravity values which are consistent with international standards, we calibrated our FG5 absolute gravimeter once a year to the one owned by National Institute of Advanced Industrial Science and Technology (AIST)which participated in the international comparative observation supported by BIPM so that we could. Furthermore, we
established 33 absolute gravity points with precise position coordinates and reviewed and unified analysis parameters such as tidal correction as new attempts. With this kind of ingenuity, we realize a highly accurate and reliable gravity network covering all over Japan.