HR: 1340h
AN: T43B-1346    [Abstracts]
TI: Coseismic Changes of groundwater level due to the 2003 M_W6.8 Chengkung Earthquake
AU: * Wang, P
EM: r96224104@ntu.edu.tw
AF: Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 106, Taiwan
AU: Chia, Y
EM: ypc@ntu.edu.tw
AF: Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 106, Taiwan
AU: Chang, Y
EM: snow72922@yahoo.com.tw
AF: Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 106, Taiwan
AU: Hu, J
EM: jchu@ntu.edu.tw
AF: Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 106, Taiwan
AU: Lee, R
EM: rhlee@wra.gov.tw
AF: Water Resources Agency, No.1340-6, Jhongjheng Rd., Wufong Township, Taichung County, 41350, Taiwan
AB: Changes of groundwater levels induced by the M_W6.8 Chengkung earthquake on 10 December 2003 were recorded in 123 out of 519 monitoring wells in Taiwan. The earthquake resulted from displacement of Chihshang fault along the Longitudinal Valley, which is the boundary between the Eurasian Plate and Philippine Sea plate in the eastern Taiwan. The 123 wells were placed primarily in the western Taiwan, ranging in depth from 12 m to 306 m. They are clustered at 90 stations located approximately 89 to 168 km from the epicenter. Among the 90 stations, 43 recorded coseismic rises, 37 recorded coseismic falls, and 10 recorded both coseismic rises and falls. The distribution of coseismic water-level changes in the Pingtung plain shows that coseismic rise predominated in most of the southwest coastal area, whereas coseismic fall prevailed in the northwest side of the plain. Base on the poroelastic theory, coseismic water-level rise is induced by compression, while coseismic water-level fall is induced by extension. During the chengkung earthquake, we found that the coseismic strain revealed by the coseismic changes of groundwater level were opposite to the perennial principal strain rates derived from the GPS data. Whether the phenomenon reflects the coseismic rebound of crustal deformation remains to be investigated. Although the peak ground acceleration decreases exponentially with hypocentral distance, the coseismic change of groundwater level does not show any trend of increase or decrease with hypocentral distances.
DE: 1800 HYDROLOGY
DE: 1829 Groundwater hydrology
DE: 1848 Monitoring networks
SC: Tectonophysics [T]
MN: 2007 Fall Meeting