Recent ground level changes in the Taipei Basin, Northern Taiwan
Speaker: Kai-Ting Fan
Abstract
Chen et al. (2007) analyzed the leveling data released from government and investigated the rate of ground level change from 1975 to 2003, which postdate the massive groundwater exploitation in Taipei area. Based on the contour maps created from the leveling data of 406 benchmarks, the overall subsidence rate in the Taipei Basin gradually decreased since 1975, and around 1989 the basin switched to slight uplift throughout a large part of the basin. Three mechanisms are proposed to be responsible for the observed land elevation changes, including shallow soil compaction, deformation within aquifer, and tectonic subsidence. The rate of shallow soil compaction is estimated about 1–8 mm/yr throughout the basin according primarily to the shallow clay thickness. Asymmetric tectonic subsidence related to the Shanchiao Fault was estimated to be 1.72 mm/yr and 0.85 mm/yr in the western part and the central part of the basin, respectively, which have removed the subsidence of prehistoric earthquakes along the Shanchiao fault (Huang et al., 2007). By subtracting the components of the soil compaction and tectonic subsidence from the surface land elevation change, the rebound of aquifer strata was estimated to be about 6.7 cm and 16 cm in western margin and Central Taipei, respectively.
Reference
Chen, C. T., J. C. Hu, C. Y. Lu, J. C. Lee, and Y. C. Chan, 2007: Thirty-year land elevation change from subsidence to uplift following the termination of groundwater pumping and its geological implications in the Metropolitan Taipei Basin, Northern Taiwan. Eng. Geol., 95, 30-47, doi: 10.1016/j.enggeo.2007.09.001.
Huang, S.-Y., Rubin, C.M., Chen, Y.-G., Liu, H.-C., 2007: Prehistoric earthquakes along the Shanchiao Fault, Taipei Basin, Northern Taiwan. Journal of Asian Earth Sciences. doi:10.1016/j.jseaes. 2006.07.025.