HR: 0800h
AN: T11D-1301    [Abstracts]
TI: Reconstruction of High-Resolution Horizontal Displacement Field Using Aerial Photogrammetry and Particle Image Velocimetry: An Example From the Taiwan Chi-Chi Earthquake Rupture Area
AU: * Chan, Y
EM: yuchang@earth.sinica.edu.tw
AF: Institute of Earth Sciences, Academia Sinica, Nankang, Taipei, 115 Taiwan
AU: Chou, S
EM: tara@earth.sinica.edu.tw
AF: Institute of Earth Sciences, Academia Sinica, Nankang, Taipei, 115 Taiwan
AU: Lee, J
EM: jclee@earth.sinica.edu.tw
AF: Institute of Earth Sciences, Academia Sinica, Nankang, Taipei, 115 Taiwan
AB: Surface displacement field may indicate 3-D fault geometry and provides basis for characterizing further fault behaviors. The GPS method reveals accurate but spatially discontinuous ground displacement because of limited number of geodetic monuments. Here we combine two digital techniques, aerial photogrammetry and particle image velocimetry (PIV), for determining the horizontal, spatially continuous ground displacement field of a portion of the Chi-Chi earthquake rupture area. We selected pairs of almost identical area of pre- and post-earthquake aerial photographs. We orthorectified the pre-earthquake aerial photograph using a previously constructed 40m DEM and several ground control points (GCPs). The post-earthquake aerial photograph was orthorectified using the same 40m DEM for avoiding systematic errors from two sets of DEM. We calibrated the coordinates of the GCPs on the hanging wall by adding GPS determined displacement vectors resulted from the earthquake, which gave best coordinate estimation of the post-earthquake GCPs. Finally, several sizes of the sliding window were used for image comparison applying the particle image velocimetry. Through these techniques, spatially continuous ground displacement field was reconstructed. The pattern indicates a clear trend of decreasing magnitude and flow-like distribution of displacement vectors towards the surface scarps on the hanging wall side. In addition, the results of the ground displacement show fault discontinuity, which generally coincides with the surface trace of Chi-Chi earthquake rupture. With simple assumptions on fault kinematics, the determined displacement pattern may provide better and more reliable constraints on 3-D fault geometry and earthquake slip distribution model.
DE: 8100 TECTONOPHYSICS
DE: 8102 Continental contractional orogenic belts
DE: 8107 Continental neotectonics
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting