GRAVITY FIELD IN TAIWAN AREA AND ITS RELATION WITH MOHO FEATURES

Newly acquired gravity data from the Taiwan area are used in this paper for revealing the characteristics of the gravity anomaly field of the region. The wavelet analysis method is for the first time introduced into gravity anomaly data processing for the area. The deep basement is also calculated for inversion of the Moho Discontinuity. The features of the basement are studied together with geological data. In this area, the free air gravity changes from -240 to 340 mGal. and the Bouguer gravity from -140 to 380 mGal. Gravity anomalies and anomaly closures of this area are all in a trend of NE and NNE direction. After analysis and comparison, it is found that the 3th order approximation of the Bouguer gravity anomaly may represent the Moho fluctuation. Data shows that the Moho depth, calculated with the Bouguer gravity anomaly data, changes from 13 to 31 km and extends in NE direction in the area. It is deeper in Taiwan Island rather than other areas and shows a thick-thin-thick pattern from northwest to southeast between 24 and 31 km. The Moho depth in the sea area to the east of Taiwan Island is much shallower in a range between 13 and 17 km. In conclusion, the Taiwan island itself based upon a continental crust, but the sea area surrounding the Taiwan Island and near the Philippine sea based on the oceanic crust.