日本地球惑星科学連合2018年大会

講演情報

[EJ] Eveningポスター発表

セッション記号 S (固体地球科学) » S-GD 測地学

[S-GD01] 重力・ジオイド

2018年5月23日(水) 17:15 〜 18:30 ポスター会場 (幕張メッセ国際展示場 7ホール)

コンビーナ:Takayuki Miyazaki(Geospatial Information Authority of Japan)、山本 圭香(国立天文台)

[SGD01-P06] Gravity anomaly map of Nagura River Basin, Western Ishigaki Island

*宮川 歩夢1名和 一成1山谷 祐介2大滝 壽樹1杉原 光彦3奥田 隆4住田 達哉1 (1.独立行政法人 産業技術総合研究所 地質情報研究部門、2.独立行政法人 産業技術総合研究所 福島再生可能エネルギー研究所、3.独立行政法人 産業技術総合研究所 地圏資源環境研究部門、4.名古屋大学大学院環境学研究科附属 地震火山研究センター)

キーワード:重力探査、絶対重力測定、石垣島

The gravity survey and gravity anomaly map reveal the geological structures. We have conducted the absolute and relative gravity measurement to understand the topographic features of the basement at Nagura River Basin, Western Ishigaki Island. Combination of absolute and relative gravity measurements is termed “hybrid gravimetry” (Okubo, 2001). The hybrid gravimetry can scale all relative measurement to gravity acceleration in the absolute sense by using an absolute gravimeter as the base of relative gravity measurements. The gravity acceleration at the VERA Ishigakijima station measured using an absolute gravimeter (FG5 #217) is g = 979002.518 mGal. We obtained gravity acceleration values using relative gravimeters at 63 stations from 2013 to 2014. The gravity acceleration values are scaled on the basis of the observed gravity acceleration at the VERA Ishigakijima station and the Gravity Standard of GSI at a meteorological observatory of Ishigakijima. We made gravity anomaly maps of Nagura river basin by compiling gravity data obtained in this study and existing database (Honda et al., 2012). Bouguer gravity anomaly gradually decreases from the Nagura Bay to the foot of Mt. Omotodake. This gravity map implies the existing of the low-density sediments in the Nagra River basin especially at the foot of the Mt. Omotodake. These results are consistent with the observation of the bowling at the foot of the Mt. Omotodake.
The gravity survey and gravity anomaly map reveal the geological structures. We have conducted the absolute and relative gravity measurement to understand the topographic features of the basement at Nagura River Basin, Western Ishigaki Island. Combination of absolute and relative gravity measurements is termed “hybrid gravimetry” (Okubo, 2001). The hybrid gravimetry can scale all relative measurement to gravity acceleration in the absolute sense by using an absolute gravimeter as the base of relative gravity measurements. The gravity acceleration at the VERA Ishigakijima station measured using an absolute gravimeter (FG5 #217) is g = 979002.518 mGal. We obtained gravity acceleration values using relative gravimeters at 63 stations from 2013 to 2014. The gravity acceleration values are scaled on the basis of the observed gravity acceleration at the VERA Ishigakijima station and the Gravity Standard of GSI at a meteorological observatory of Ishigakijima. We made gravity anomaly maps of Nagura river basin by compiling gravity data obtained in this study and existing database (Honda et al., 2012). Bouguer gravity anomaly gradually decreases from the Nagura Bay to the foot of Mt. Omotodake. This gravity map implies the existing of the low-density sediments in the Nagra River basin especially at the foot of the Mt. Omotodake. These results are consistent with the observation of the bowling at the foot of the Mt. Omotodake.