Bulletin of the Seismological Society of America; April 2005; v. 95; no. 2;
p. 471-485; DOI: 10.1785/0120020170
© 2005 Seismological Society of America
Structures Associated with the Northern End of the 1999 Chi-Chi Earthquake Rupture, Central Taiwan: Implications for Seismic-Hazard Assessment
Yuan-Hsi Lee1,
Shih-Ting Lu2,
Tung-Sheng Shih2,
Meng-Long Hsieh3 and
Wei-Yu Wu2
1 Department of Earth and Environmental
Sciences
National Chung-Cheng University
Chiayi, Taiwan, Republic of
China
(Y.-H.L.)
2 Central Geological Survey, Republic
of China
P.O. Box 968
Taipei, Republic of China
(S.-T.L.,
T.-S.S., W.-Y.W.)
3 Department of Geological
Science
National Taiwan University
245 Choushan Road
Taipei, Taiwan,
Republic of China
(M.-L.H.)
The surface rupture of the 1999 Chi-Chi earthquake (Mw
7.6) trends more than 100 km in a north–south direction. Surface
deformation at the northern end stops abruptly at an area between the Tachia
River and the Taan River where a broad pop-up structure with east to northeast
strike can be found that has a trend different from the
north–south-striking main thrust. We combine the absolute elevation data
before and after the Chi-Chi earthquake to obtain the regional vertical
displacement and the magnitude of the pop-up structure. The greatest uplift
could reach as high as 15–16 m. Using deformation magnitude and the
area-balancing method, we measure the depth of the detachment to show the
subsurface geometry of the Chelungpu fault at its northern end. This shows that
the geometry of the Chelungpu fault controls termination of the surface rupture
and the depth of the detachment controls the amount of deformation.
Copyright © 2009 by Seismological Society of America