Characterizing the Hsincheng active fault in northern Taiwan using airborne LiDAR data: detailed geomorphic features and their structural implications

Neotectonic studies usually involve detection of minor elevation changes; high-resolution elevation data are needed for efficiently characterizing these small changes in topography. We apply airborne LiDAR data to study a segment of the Hsincheng fault, a well-known active fault near a science-based industrial park in northern Taiwan. The Hsincheng fault has received much attention and studies in the past; but high-resolution digital elevation models have not been applied to the study of the fault and its surrounding structures. We processed the newly acquired LiDAR data and produced upto 1m x 1m DEMs to investigate the active fault adjacent to the populated industrial park in Taiwan. Using the high-resolution LiDAR DEMs, aerial photographs and topographic maps, we show highly detailed geomorphic features around the study area of the Hsincheng fault. There are three major characteristics of the study area: three very well developed river terraces at varying levels, the fault/fold scarp of the Hsincheng fault, and a meander river system. Using the LiDAR DEMs, we were able to detect, with precision, several fault/fold scarps and very gentle NE-trending folds of the river terraces. Back-thrust appears to be present between two gentle anticlines of the river terraces. Along the Hsincheng fault scarp, several minor but obvious E-W trending scarps are present. Because the orientations of these scarps are quite different from the Touchien river, we interpret these scarps to be fault or fold scarps instead of terrace risers. Based on the above observations and analyses, we conclude that: First, airborne LiDAR data are important for detailed analyses of structural and geomorphic features, at a scale practical to people. Second, the area of the Hsincheng fault shows two structural systems -- the major one trends about NNE, and the minor one trends about EW. The mixed structural systems may be resulted from the study area being adjacent to the Hsinchu thrust fault ­V an E-W trending high-angle thrust fault just to the north. Third, the Hsincheng fault may not have a large component of left-lateral movement as people argued previously. Judging from the alignment of the terrace risers and the Hsincheng fault, it is possible to have such apparent left-lateral movement even with pure thrust fault.