Abstract
The recent dramatic increase in millimeter- to centimeter- resolution topographic datasets obtained via multi-view photogrammetry raises the possibility of mapping detailed offset geomorphology and constraining the spatial characteristics of active faults. Here, for the first time, we applied this new method to acquire high-resolution imagery and generate topographic data along the Altyn Tagh fault, which is located in a remote high elevation area and shows preserved ancient earthquake surface ruptures. A digital elevation model (DEM) with a resolution of 0.065 m and an orthophoto with a resolution of 0.016 m were generated from these images. We identified piercing markers and reconstructed offsets based on both the orthoimage and the topography. The high-resolution UAV data were used to accurately measure the recent seismic offset. We obtained the recent offset of 7 ± 1 m. Combined with the high resolution satellite image, we measured cumulative offsets of 15 ± 2 m, 20 ± 2 m, 30 ± 2 m, which may be due to multiple paleo-earthquakes. Therefore, UAV mapping can provide fine-scale data for the assessment of the seismic hazards.
Highlights
High-resolution three dimensional (3D) data are essential for constraining the spatial characteristics of active faults as they provide a fundamental dataset for mapping the complexity of faulting and the details of the surficial features offset by the faults
Systematic sinistral offsets of alluvial fans, fluvial terraces, risers and channels are observed all along the fault, whose principal trace is remarkably sharp and linear, indicating sustained active tectonic movement (Fig. 3). We conducted this Unmanned Aerial Vehicles (UAV)-based investigation to further constrain the spatial characteristics of the ATF, to validate the offset obtained by the previous study, i.e., approximately 20 m16, and to measure the recent small seismic offset
By using the high resolution data, especially the contour lines derived from the digital elevation model (DEM), we were able to identify micro-scale geomorphic markers, which helped to add important constraints on the small offsets (Fig. 7)
Summary
High-resolution three dimensional (3D) data are essential for constraining the spatial characteristics of active faults as they provide a fundamental dataset for mapping the complexity of faulting and the details of the surficial features offset by the faults. With the currently available satellite images (Fig. 2a,b and c), it is difficult to interpret the offset created by the most recent earthquake (MRE) or small cumulative offsets Targeting this problem, our investigation aims to obtain high resolution data to provide accurate measurements of these recent offsets. Systematic sinistral offsets of alluvial fans, fluvial terraces, risers and channels are observed all along the fault, whose principal trace is remarkably sharp and linear, indicating sustained active tectonic movement (Fig. 3) We conducted this UAV-based investigation to further constrain the spatial characteristics of the ATF, to validate the offset obtained by the previous study, i.e., approximately 20 m16, and to measure the recent small seismic offset
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