Subsurface Structures of the TaipeiBasin from Gravity Data

Chen-Fong Yu

Abstract

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.