Based on tensor decomposition technique, we have analyzed the dimensionality of magnetotelluric (MT) data and propose a 2-D electrical model characterized by a high conductive anomaly beneath Sanyi-Puli seismic zone, a distinct NW-SE trending linear seismic zone in the fold-thrust belt of NW Taiwan. Fluid pressurization indicated by the highly conductive anomaly may result in the active seismicity in Sanyi-Puli seismic zone and, particularly, may also induce the large slip associated with high static stress drop in the northern part of the fault rupture process for the 1999 Chi-Chi, Taiwan, earthquake.