Slip distribution and tectonic implication of the 1999 Chi-Chi, Taiwan, Earthquake

We report on the fault complexity of the large (M-w = 7.6) Chi-Chi earthqua ke obtained by inverting densely and well-distributed static measurements c onsisting of 119 GPS and 23 doubly integrated strong motion records. We sho w that the slip of the Chi-Chi earthquake was concentrated on the surface o f a "wedge shaped" block. The inferred geometric complexity explains the di fference between the strike of the fault plane determined by long period se ismic data and surface break observations. When combined with other geophys ical and geological observations, the result provides a unique snapshot of tectonic deformation taking place in the form of very large (> 10m) displac ements of a massive wedge-shaped crustal block which may relate to the chan geover from over-thrusting to subducting motion between the Philippine Sea and the Eurasian plates.