台湾地区重力场特征及莫霍面反演

GRAVITY FIELD IN Taiwan Region AND ITS RELATION WITH MOHO FEATURES

台湾地区空间重力异常幅值在-240~340mGal之间变化,布格重力异常幅值在-140~380mGal之间变化,重力异常及圈闭走向呈现北东、北北东向。将小波分析方法引入台湾地区的重力异常数据处理,经过分析比对,台湾地区布格重力异常小波分析三阶逼近结果代表莫霍面起伏形态,利用重力数据反演了深部界面莫霍面,研究区莫霍面深度为12~32km,莫霍面展布呈现北东走向,台湾岛区莫霍面深,在24~31km之间变化,由西北往东南为厚-薄-厚分布,台湾东部海区莫霍面深度浅,在12~17km之间变化,台湾岛属于陆壳结构,靠近菲律宾海的台湾岛外海地区,属于海洋性地壳结构。

Newly acquired gravity data from the Taiwan Region are used in this paper for revealing the charac- teristics of the gravity anomaly field of the region. The wavelet analysis method is for the first time intro- duced 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 reGal, 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. Af- ter 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 Is- land 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 be- tween 13 and 17 km. In conclusion, the Taiwan island itself based upon a continental crust, but the sea ar- ea surrounding the Taiwan Island and near the Philippine sea based on the oceanic crust.