為了更加了解地下構造，本研究選用位於台灣中南部及橫跨海峽地區六條速度模型來進行密度模型的模擬，希望能藉此了解該地區速度與密度之間的關係。 模擬過程中，首先假設岩層密度與P波速度為一個簡單的線性關係，將速度模型轉換為密度模型之後，在計算其密度模型所對應的理論重力異常值並與觀測重力異常值一起做比對，這些由速度直接轉密度的初始模型，其計算值幾乎皆低於觀測值，對此進行初步的討論。接著進行修改密度去擬合計算值與觀測值，如有必要會對其地下形貌進行調整。 根據模擬的結果，除了對地下形貌與原速度模型進行討論比較外，皆發現各模型的淺中層密度有低估的情形存在，這表示原始速度模型的淺中層速度也有被低估。 另外本研究將各模型原始速度、原始密度、與調整後密度一起進行速度與密度相關式討論與比較，計算出的海峽地區相關式可提供後人做密度模擬及逆推的參考，而台灣地區地下構造複雜，因此地下形貌的調整較多，其相關式參考價值不大。最後從各模型的趨勢線發現速度的變化在深部較線性，越往淺層則呈現非線性的情況。 In order to better understand the subsurface structure. In this study, we use six velocity models in central and southern Taiwan to create the new density models. Hope to learn more about the relationship between velocity and density in this area. In the process of model building. First, assuming rock density and P-wave velocity is a simple liner relationship. After the velocity model is converted to density model. We calculate the theoretical gravity anomaly of the density models to compare with the observe gravity anomaly. Make a preliminary discussion of these models. Then modify it to fit the density calculated and observed values, if necessary, we will adjust its underground topography. According to the modeling results, we found that all the models underestimate the density in shallow and intermediate stratums. It means that the value of velocity in shallow stratums has been underestimated. And we conducted a discussion about the relationship between velocity and density by making the correlations in Taiwan and Taiwan strait area. Strait area correlations can provide a reference in making a new density model or combined density model inversion. Final, we found that velocity variations in deep stratums are linearly, and nonlinear variations in shallow stratums.
