Comment on “A Vertical Exposure of the 1999 Surface Rupture of the Chelungpu Fault at Wufeng, Western Taiwan: Structural and Paleoseismic Implications for an Active Thrust Fault,” by Jian-Cheng Lee, Yue-Gau Chen, Kerry Sieh, Karl Mueller, Wen-Shan Chen, Hao-Tsu Chu, Yu-Chang Chan, Charles Rubin, and Robert Yeats

Lee et al. (2001) applied the line-length balance method on the deformed soil to calculate the shortening of the surface rupture on Chelungpu Fault at Wufeng, Western Taiwan. Their results showed a shortening of 3.3 m and a total slip of 4 m. We, on the other hand, calculated the slip vector of the surface rupture by restoring the deformed concrete fence and found that the horizontal slip is 1.77 m and the slip direction is 279°. We then combined the horizontal slip vector with the vertical slip (2.1 m) to get a net slip of 2.75 m. The shortening we had in hand was 1.76 m, which was only half of Lee et al.'s (2001) data. We thus applied the area-balance method to check whether the data measured by line-balance method are reasonable.