| 講演要旨(和文) | | 5万分の1地質図幅「川俣」において，GPS測量による高精度の重力データと従来の重力データを使用して，重力図の編集を行った．重力データの精度に差が大きいため，GPS測点の近くにある地形図測点は使用せず，また，地形図測点のデータにGPS測点の1/30の重みを付けて解析を行った．重力図の編集では，仮定密度2.60g/cm3のブーゲー異常図と残差重力図を作成し，また，重力データから地殻表層密度の推定を行った．その結果，麓山，白馬石山，南移等で見られる斑れい岩の分布と高重力異常・高岩石密度分域が良く対応し，また，新規花崗岩の分布域，岩倉層のような火山岩の分布する地域が，低重力異常で地殻表層密度も低く推定されることが分かった． |
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| | 講演要旨(英文) | | A new gravity map, Bouguer anomaly map, of the Kawamata district has been compiled. Gravity data within the map area comprise 1405 stations including 68 newly added gravity stations. The density value used for both Bouguer and terrain corrections is 2.60 g/cm3. We also present two additional maps, which show gravity residual anomalies with the regional Bouguer anomalies removed, and surficial rock density distribution map. The Bouguer anomaly map and additional maps revealed the following features: (1) High gravity anomalies correspond to around the gabbroic rocks are distributed. (2) A circular low gravity anomaly with a diameter of 2 km in Terasaka area is inferred due to Iwakura formation. (3) Regions of younger type granitic rocks distributed in southwestern part of the map area correspond roughly to gravity anomalies lower than their surroudings. |
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