Recent movement of the Late Pleistocene Shoushan slump, southwestern Taiwan, based on landform surveys

This study aims to investigate and to analyze the recent complex mass movements of Shoushan in Kaohsiung City, southwestern Taiwan, by the short-term global positioning system (GPS) survey and the comparison of elevation data from different sources. Landform change is derived from difference of 5-m digital elevation models (DEMs), i.e., the DEMs of difference (DoD), which are abstracted from 1:5000 scale contour maps dating to 1978 and 1998. The spatial distribution of elevation change within the study area is visualized and delineated by the threshold value of 2.5 m which is resulted from the error level of contour maps. The GPS survey of benchmarks is deployed to infer the short-term surface movement in the study area, and to argue with the results of DoD analysis. To ensure the reliability of GPS field measurements, a 6-h static surveying procedure is applied to each benchmark with the reference GPS station being positioned in a tectonically stable location close to the study area. Based on the GPS survey results and the DoD analysis, the study identifies the development of several secondary slumps on the main body of the huge slump. The secondary slumps are characterized by relatively slow movements with diverse directions.