在台灣本島布蓋重力圖中，重力異常值的走向趨勢和地質構造有一定的關係；如台中盆地和屏東地區皆因為沉積層而呈現重力低區，而台北盆地是一明顯的沉積盆地，上覆鬆軟的第四紀沉積層，根據鑽井資料顯示其沉積層厚度在數十公尺到七百公尺之間，但在重力異常圖中並未表現出此低區，為了探討此現象，本研究利用觀測重力資料所得的重力異常值與重力初始模型所得的理論重力值比對，以期得到一合理的地下密度構造。
在初始模型的假設方面，利用了此地區現有速度構造，並使用速度和密度的轉換關係式（Barton,1986），將速度構造轉換成密度構造，加上此地區的震測資料及鑽井資料，來建立重力初始模型，最後利用初始模型順推出理論重力值。
不論是觀測重力資料得到的剩餘重力異常，還是在深度1公里的模型所順推出的理論重力值，其重力效應都很小，可見盆地內沉積層不是影響重力的主要原因，而是來自於深部地層的效應。於是進一步將深度加深，使用深度6公里的模型順推出的理論重力值來與觀測值比對，得到較合理的密度模型。
台北地區的重力異常圖可從模型剖面的結果配合地質環境來解釋，林口台地相對來說密度較低且地層較連續，台北盆地的沉積層較薄且底下為不整合的第三紀地層，相對來說密度較高，而大屯火山群由於火成岩分佈的關係，相對來說密度也較高，造成台北地區的重力值大致上東高西低，但在等值線進入盆地後有向北轉折的情形。另外盆地本身的沉積層很薄，底下為不整合的第三紀地層，且盆地的範圍太小，加上周圍地質環境的影響，使得盆地無法表現出一重力低區。

In the gravity anomaly map of Taiwan, the isogals trends are generally in consonance with the structural trends. The gravity lows are usually found in sedimentary basin like Taichung basin and Pington area but the Taipei basin is a conspicuous sedimentary basin over by late Quaternary sediments in north Taiwan, without presenting a gravity low in gravity anomaly map. In order to understand the cause, we use the gravity anomaly values modeling substructure to get the reasonable
and reliable subsurface density structure.
About the assumption of the initial density model, we use the converted formula (Barton, 1986) converting the tomography model in north Taiwan by Kim et.al (2005), seismic reflection record and well drilling log.
After preliminary modeling, the shallow sediments only show the weak gravity anomaly and the major gravity anomaly effects are caused by the influence of deeper layers.

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