| dc.description.abstract | A more reliable subsurface structure can be obtained by combining both of the seismic and gravity data. To gain a better understanding in the central Taiwan, the seismic and gravity data were collected in summer, 2000. The seismic profile approximately perpendicular to the geological strike of Taiwan, were deployed 60 seismic instruments with an average spacing of 2 km. In the mean time, gravity survey was also made along this seismic profile to obtain the Bouguer anomaly distribution. In the modeling of subsurface density structure, available seismic data are used wherever possible to constrain the geometric and/or densities. We simply assumed that there is a direct relationship between density and velocity without any further consideration. Unfortunately, the calculated Bouguer anomaly from the velocity structure doesn’t match well with the observed Bouguer anomaly except the western segment. We also try to calculate Bouguer anomaly from other 2-D velocity structures taken from the previous 3-D velocity models. To study the compatibility between the density and velocity structures should be as a more important research topic in Taiwan. Finally, the reliable density structure across central Taiwan is obtained from the gravity data. In substance, the structure is simply in the western segment but complex in the eastern segment. According to the simulated result, the crustal deformation due to the collision between Eurasia Plate and Philippine Sea Plate caused the result that the depth of the upper crust obviously increases and the deepest position of the Moho discontinuity appears below the Central Range. Across the eastern Central Range, the crustal type transfers from the continental crust to the oceanic crust so that the Moho discontinuity becomes shallow. In the profile near Hualien, with the transition of plates, there are a heavy deformation at the upper crust and a lower density region in the depths. The results show that the velocity structure obtained by seismic investigation had a good constrain in depth. Therefore, we can obtain a more reliable subsurface structure by using the velocity structure to control the deep conformation and using the gravity and geological data to control the shallow conformation. | en_US |