Abstract
Steep topographic reliefs and heavy vegetation severely limit visibility when examining geological structures and surface deformations in the field or when detecting these features with traditional approaches, such as aerial photography and satellite imagery. However, a light detection and ranging (LiDAR)-derived digital elevation model (DEM), which is directly related to the bare ground surface, is successfully employed to map topographic signatures with an appropriate scale and accuracy and facilitates measurements of fine topographic features. This study demonstrates the efficient use of 1-m-resolution LiDAR for tectonic geomorphology in forested areas and to identify a fault, a deep-seated landslide, and the regional cleavage attitude in southern Taiwan. Integrated approaches that use grayscale slope images, openness with a tint color slope visualization, the three-dimensional (3D) perspective of a red relief image map, and a field investigation are employed to identify the aforementioned features. In this study, the previously inferred Meilongshan Fault is confirmed as a NE–SW-trending, eastern dipping thrust with at least a 750 m-wide deformation zone. The site where future paleoseismological studies should be performed has been identified, and someone needs to work further on this site. Signatures of deep-seated landslides, such as double ridges, trenches, main escarpments, and extension cracks, are successfully differentiated in LiDAR DEM images through the use of different visualization techniques. Systematic parallel and continuous lineaments in the images are interpreted as the regional cleavage attitude of cleavage, and a field investigation confirms this interpretation.
Highlights
Active faults and deep-seated landslides frequently occur in the mountainous regions of Taiwan, which is located in a tectonically active environment and in a sub-tropic climatic zone
light detection and ranging (LiDAR) data are used to produce a digital elevation model (DEM), which is directly related to the bare ground surface and provides useful information on fine topographic features that cannot be detected under heavy vegetation and underbrush conditions [9,10,11]
Because of its high resolution and precision, airborne LiDAR has led to a marked growth in terrain information and has facilitated the detection of fine-scale tectonic-geomorphic features required for understanding geological surface processes and the quantitative exploration of the characteristics of tectonic geomorphology [12,13,14,15,16,17]
Summary
Active faults and deep-seated landslides frequently occur in the mountainous regions of Taiwan, which is located in a tectonically active environment and in a sub-tropic climatic zone. Because of its high resolution and precision, airborne LiDAR has led to a marked growth in terrain information and has facilitated the detection of fine-scale tectonic-geomorphic features required for understanding geological surface processes and the quantitative exploration of the characteristics of tectonic geomorphology [12,13,14,15,16,17]. This technique has recently been used to map fault zones and deep-seated landslides with extraordinary detail and aerial coverage [18,19,20]. Because LiDAR-derived DEMs offer a markedly higher spatial resolution than present topographic maps and aerial photos, they allow us to map the locations of fault traces and deep-seated landslides more accurately than was previously possible
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