利用衛星測高儀與船測重力推算西太平洋海上重力場

Abstract

西太平洋地區的海上詳細重力場在此由四種衛星資料(Seasat, Geosat, ERS-1與TOPEX/POSEIDON)和船測資料使用最小二乘配置法求得。船測重力 資料先由衛星重力以二次多項式對時間改正，再與衛星資料聯合求得結合 重力場。在配置法推算過程中，則以OSU91A模式作為去除回復技術的參考 場。為試驗配置法的可行性，先以靠近臺灣東部的海上地區作衛星重力的 計算，並與實際船測重力作比較。而實際針對南海地區的重力異常推算， 則是經過特殊調整過程來去除不尋常的船測重力。我們亦比較由配置法所 得重力與Sandwell用快速傅利葉方法所得重力，結果發現前者較後者接近 船測重力。西太平洋重力場不僅表達了與現有海底地形的高相關性且顯示 該地區的詳細板塊構造。 A detailed marine gravity field over the Western Pacific Ocean were derived from Seasat, Geosat, ERS-1 and TOPEX/POSIDON altimeter and shipborne gravity data using least-squares collocation (LSC). The ship gravity were first adjusted by a satellite data to yield a combined gravity field. The OSU91A geopotential model was used in the remove/restore technique employed in the collocation computation. To validate the LSC, we calculated a satellite-only gravity over a region east of Taiwan and compared the result with ship gravity. The computation of gravity was then carried out over the China Sea with specially tuned procedure to eliminate spurious ship gravity. We also compared the LSC gravity with Sandwell's FFT- derived gravity and conclude that the former is better than the latter in terms of agreement with the ship gravity. The derived gravity over the Western Pacific Ocean shows high correlation with the existing bathymetry and reveals detailed tectonic structures.