Fault Trace of Shanchiao fault extended from Shanhsia to Kuantu along the west margin of Taipei basin and then pass through the Tatun volcano. Fault trace in the Tatun volcano area is covered by colluvium or vegetation so there are many arguments about it. But as it extends to Chinshan plain it is conformed by the linear scarp in the north(figure.1).
　

       By the analysis of 3 core-boring data in Chinshan plain it presents it was a subaerial river environment before 8390-8180 yr BP, then the sea water flooded the land to form brakish lagoon environment in CS-2 (figure.2). But from CS-1 and CS-3 it presents the sea water flooded into the basin before 9560-9450 yr BP in the central part of the plain. The timing delay of the flooding event in CS-2 might relate to the colluvium deposited from the nearby fault scarp which make it a topography high. After Late Holocene ( 6,000 yr BP) the eustatic sea level reaches a stable condition and the fluvial deposit gradually prograded to the coastal area.
　

       From the dating and paleoenvironment of the CS-3, we estimate the long term crust deformation rate as follows: the CS-1 has a mean 0.7±0.5 mm/yr uplift rate. The CS-2 has a mean 0.3±0.6 mm/yr uplift rate and 0.6±0.6 mm/yr if ignorance of -1.0±0.7 mm/yr. The CS-3 has a mean -0.4±0.6 mm/yr subsidence rate. These 3 sites display no obvious vertical crust deformation, just CS-3 displays a slight subsidence. Chinshan plain and Taipei basin might be in the hanging wall of Shanchiao fault, and be part of a half graben structure. The subsidence rate will be getting larger as close to the fault trace and getting smaller or converse to uplift as away from fault trace. CS-1 and CS-3 sites in the south area of the plain display a little uplift and subsidence rate. The phenomenon agrees with the half graben structure. But the CS-2 which is closest to the fault trace display a subtle uplift, we suggest the site might be located in footwall (figure.2).
　

Figure.1 Localities of core-boring site in Chinshan plain. (aerial photo extract from “Google Earth” website)

Figure.2 Cross-section of Chinshan plain constructed by core-boring data.