The Gravity Field in the Taiwan Strait

Gravity surveys were carried out in the western part of the Taiwan Strait by the South China Sea Institute of Oceanology, Academia Sinica, from 1986-1989. Based on these data, along with data from the east and southeast parts of Taiwan Strait collected by the University of Tokyo, Lamont-Doherty Geological Observatory, and the U.S.S.R, gravity maps of Taiwan Strait have been compiled at a scale of 1:2,000,000 with a contour interval of 5 mGal. These maps cover part of the East China Sea and South China Sea, where good gravity data exists. Comparison of data from different sources in the same area indicates a very good agreement. These maps, for the first time, give detailed gravity information on the Taiwan Strait and are, thus, very useful for tectonic study and oil exploration in that area. The relationship between gravity anomalies and sedimentary basins has been studied. Most of the data show that the gravity low corresponds to the basin areas and the gravity high is related to tectonic structural highs. The Xia-Peng depression, Wuqiuyu depression, and Xinzhu depression, for example, exhibit gravity lows. The gravity profiles also clearly show this relationship. The authors think the undulation of gravity anomalies is closely related to tectonic structures. In addition, some main faults can been confirmed by the gravity maps. The calculated crustal thicknesses range from 30 to 25 km along profile C-C.