Reconstructing the Geometry of the Yushu Fault in the Tibetan Plateau Using TLS, GPR and Trenching

Abstract

Although geomorphic evidence and shallow geometry of active faults are significant for the understanding and assessing of fault activity and seismic hazards, it is challenging to acquire high-resolution topographic data and shallow geometry of the Yushu fault by conventional methods. Here, we present a case study to reconstruct the detailed surficial and subsurface geometry of the Yushu fault using terrestrial laser scanning (TLS), multi-frequency ground penetrating radar (GPR) and trenching. TLS was suitable for measuring the high-resolution three-dimensional (3D) topographic data of the fault. GPR surveys with different frequency antennas (25 MHz, 100 MHz, 250 MHz and 500 MHz) were conducted to image the shallow geometry of active faults at different depths and spatial resolutions. The typical groove landscape, parallel to surface traces of the fault, was clearly observed on the TLS-derived data. A ~40 m width narrow fault system and three faults were identified on the different frequency GPR profiles. Furthermore, faults F1 and F2 were supposed to be boundary faults but were sinistral-lateral strike-slip faults with a normal component, while fault F3 was inferred as the secondary fault. The western trench section, despite the limited investigation depth (~2 m), was well consistent with the 500 MHz GPR result, especially in the location of fault F2. Finally, a 3D surficial and subsurface model was established from the TLS-derived data and GPR data offering multi-sensor and multi-view spatial data to characterize and understand the fault’s kinematics and characteristics. In addition, the shallow geometry of the fault on the GPR results would be better interpreted with the help of the corresponding surficial data. The study results demonstrate that a combination of TLS, multi-frequency GPRs and trenching can be successfully used for reconstructing a detailed surficial and subsurface geometry of the Yushu fault. It will play an increasing role in comprehensive understanding and assessing fault behavior and seismic hazards, especially on the Tibetan Plateau and the adjacent area.

Multisensor and Multiscale Data Integration Method of TLS and GPR for Three-Dimensional Detailed Virtual Reconstruction

“…In recent years, the integration of TLS and GPR has been gradually used in cultural heritage protection [ 9 , 12 , 17 , 19 , 25 , 26 ], urban infrastructure detection [ 27 , 28 , 29 ], bridge structure assessment [ 8 , 30 , 31 , 32 ], geology investigations [ 33 , 34 , 35 , 36 ], glacier detection [ 37 ], and other applications. Spahic et al [ 38 ] rebuilt a 3D model of fault outcrop in the Gocad v2009 software using T-LiDAR point clouds and GPR images.…”

“…Zhang et al [ 42 ] provided data visualization of fault scarps in Bentley Pointools 1.5 software using TLS point clouds and GPR data. Zhang et al [ 36 ] used TLS-derived data and 2D GPR images to reconstruct a 3D surficial and subsurface model of the Yushu fault. Previous research on the data fusion method of TLS and GPR mainly focused on two aspects.…”

“…This has the advantage of quickly realizing the data integration of TLS and GPR with different data formats, but the multiperspective spatial data were only displayed in the same scene. Second, the GPR data were transformed to scattered point clouds; then, the point cloud and GPR data were merged into a single point cloud dataset for data visualization [ 9 , 36 , 38 , 42 ]. Although a limited number of studies have presented cases for data integration of TLS and GPR in the scattered point cloud form, a reliable systematic methodology is still scarce.…”