0 10 4 P3 P2 P1 IEEE GEOSCIENCE AND REMOTE SENSING MAGAZINE 0 N 100 200 (m) (a) 20161126 20161126 20161126 P3 P2 P1 20170519 20170519 20170730 20170730 20170308 20170730 20170928 Displacement Trends 20170519 Failure on 20171001 Accelerating From 20170916 20170308 20170308 Measured Displacement (e) -10 20160921 -8 -6 -4 -2 (d) -10 20160921 1 0 -8 -6 -4 -2 (c) -10 20160921 1 0 -8 -6 -4 -2 1 0 FIGURE 4. The pre-event displacements of the Dangchuan 4# landslide revealed by L-band observations. (a) The mean velocity map from time-series InSAR analysis. (Source: Google Earth; used with permission.) (b) The enlarged active displacement area and the location of points P1, P2, and P3. The displacement time series for points (c) P1, (d) P2, and (e) P3, respectively. Landslide Boundary -10 (cm/Year) (b) Accumulated Displacement (cm) Accumulated Displacement (cm) Accumulated Displacement (cm) 142 MARCH 2020