10:15 AM - 10:30 AM
[SGD02-06] Improvement of method that makes Japanese old and dense gravity data consistent with Japan gravity standardization net 2016
Keywords:Japan Gravity Standardization Net. 2016 (JGSN2016)
GNSS-derived orthometric height determination has been recently developed. As a result, the importance of land gravity data densely covering the whole country has been gradually increasing because the data has been increasingly utilized as fundamental data for modeling of geoid, a reference surface for orthometric height. The latest, Highly-reliable land gravity data covering the country are essential for improving accuracy and reliability of geoid model. However, it is almost impossible to obtain new data referring JGSN2016 with in short period by newly conducting time- and cost-consuming land gravity measurement for the whole country.
To resolve these problems, we have developed a method that makes Japanese old and dense gravity data consistent with JGSN2016. We reported a solution for that problem in JpGU2016. In the method, we estimated uplift/subsidence displacement of observation station due to crustal deformation, mass redistribution caused by earthquake event and system offset that has existed since establishment of each gravity reference individually. Consequently, we achieve to convert old gravity data to new gravity data in about 40 micro Gal precision. In the method, however, vertical gravity gradient value which is used for convert uplift/subsidence displacement of station to gravity change is assumed that all station have same vertical gravity gradient (Bouguer) value. Therefore spatial variation of vertical gravity gradient is abbreviated.
We newly developed gravity terrain correction program that use 10m mesh DEM data provided by GSI. And we calculated vertical gravity gradient of each station for more precise estimation. In addition, we will present method for calculating displacement of station that takes into account fault geometry and estimation for system offset using data assimilation.
By this research, gravity change that are caused by crustal deformation is estimated. And relation of old and new gravity data is revealed. Thus old and dense gravity data recover accuracy. Consequently, basic data for developing more precise geoid are provided.