UAV-based surveying in volcano-tectonics: An example from the Iceland rift

Bonali, Fabio Luca; Tibaldi, Alessandro; Marchese, Fabio; Fallati, Luca; Russo, Elena; Corselli, Cesare; Savini, Alessandra

doi:10.1016/j.jsg.2019.02.004

Cited by 70 publications

(66 citation statements)

References 96 publications

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“…Ground truthing and quality control of the resulting DEMs was acquired by including reference objects of known dimensions in our models. Our model accuracy lies within the same error range as in Bonali et al, (2019b), who achieved accuracies between 0.04 m -0.07 m for 50 m -100 m flight altitude horizontally and up to ca. 20 cm vertically, thus below and within the same order of magnitude as our mapping accuracy.…”

Section: Ground Truthing and Field Observationssupporting

confidence: 76%

“…Our method is similar the one used by (Bonali et al, 2019b) who collected data from 50 and 100 m altitude and have shown 5 that with these setting one obtains sufficient resolution for detailed analysis of faults and fissures. We did not place further ground control points (GCPs) and relied on the integrated GPS receiver of the UAV in favor of time efficiency, since absolute elevations are not relevant to our research goals.…”

Section: Unmanned Aerial Vehicle Photogrammetry 20mentioning

confidence: 99%

“…They have been applied successfully to e.g. aid the mapping of faults and joints (Bonali et al, 2019b;Vasuki et al, 2014), landslides (Niethammer et al, 2012), or moss beds (Lucieer et al, 2014). The data for this study was acquired using three different UAVs: the DJI Phantom 4 and Mavic pro with 12 MP sensors and the Phantom 4 Advanced, with a 20 MP sensor.…”

Section: Unmanned Aerial Vehicle Photogrammetry 20mentioning

confidence: 99%

“…The correlation of piercing points of adjacent fracture walls as presented in Bonali et al, (2019b) is more accurate for fissures with small opening width with respect to larger opening widths. More correlation points can be found directly on the fracture walls.…”

Section: Ground Truthing and Field Observationsmentioning

confidence: 99%

“…The apparent opening width of fissures at the surface can be strongly misestimated when not directly measured at the rock surface: erosion of soil-cover into the fracture leads to funnel shape on the surface, causing overestimation of the opening as also described in Bonali et al, (2019b). We further observed the reduction of visible opening width by vegetation that i) is 5 large enough to prevent a clear line of sight on the fracture when seen from above and ii) moss and lichen patches that grow over the edges, thus reducing the visible opening ( Fig.…”

Section: Ground Truthing and Field Observationsmentioning

confidence: 99%

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Structure of massively dilatant faults in Iceland: lessons learned from high resolution UAV data

Weismüller

Urai

Kettermann

et al. 2019

Preprint

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Normal faults in basalts develop massive dilatancy up to several tens of meters close to the Earth's surface and show corresponding interactions with groundwater and lava flow. These massively dilatant faults (MDF) are widespread in 15 extensional settings like Iceland or the East African Rift, but their detailed geometry is not well understood, despite their importance for fluid flow in the subsurface, geohazards or geothermal energy. We present a large set of digital elevation models (DEM) of the surface geometries of MDF with 5-15 cm resolution, acquired along the Icelandic Rift zone using unmanned aerial vehicles (UAV). UAV provide a much higher resolution than aerial/satellite imagery and a much better overview than ground-based fieldwork, thus bridging the gap between outcrop scale and regional observations. 20Our data present representative outcrops of MDF, formed in basaltic sequences linked to the Mid Ocean Ridge. We acquired photosets of overlapping images along about 20 km of MDF and processed these using photogrammetry to create high resolution DEMs and ortho-rectified images. We use this dataset to map the faults and their damage zones to measure length, opening width and vertical offset of the faults and identify surface tilt in the damage zones. Ground truthing of the data was done by field observations. 25Mapped vertical offsets show typical trends of normal fault growth by segment coalescence. However, opening widths in mapview show variations at much higher frequency, caused by segmentation, collapsed relays and tilted blocks. These effects cause a commonly higher than expected ratio of vertical offset and opening width for a steep normal fault at depth.Based on field observations and the relationships of opening width and vertical offset, we define three endmember morphologies of MDF: (i) dilatant faults with opening width and vertical offset, (ii) tilted blocks (TB), and (iii) opening mode 30 (mode I) fissures. Field observation of normal faults without visible opening invariably shows that these have an opening filled by recent sediment. TB dominated normal faults tend to have a largest opening width with respect to vertical offsets. Fissures Opheim and Gudmundsson, 1989). The bedrock is mostly of volcanic origin with ages increasing with distance from the rift (Fig. 2). The succession of lava flows with cooling joints, paleo-soils and hyaloclastite result in locally complex mechanical stratigraphy. Faults and fissures crosscutting this mechanically heterogeneous section reactivate the pre-existing cooling joints close to the surface, leading to complex geometries (Forslund and Gudmundsson, 1991;Gudmundsson, 1987a; Gudmundsson 5 and Bäckström, 1991;Hatton et al., 1994).

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Section: Ground Truthing and Field Observationssupporting

confidence: 76%

Section: Unmanned Aerial Vehicle Photogrammetry 20mentioning

confidence: 99%

Section: Unmanned Aerial Vehicle Photogrammetry 20mentioning

confidence: 99%

Section: Ground Truthing and Field Observationsmentioning

confidence: 99%

Section: Ground Truthing and Field Observationsmentioning

confidence: 99%

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Structure of massively dilatant faults in Iceland: lessons learned from high resolution UAV data

Weismüller

Urai

Kettermann

et al. 2019

Preprint

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Unmanned aerial vehicle oblique photography‐based superposed fold analysis of outcrops in the Xuhuai region, North China

Lai

Liu

et al. 2020

Geological Journal

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Unmanned aerial vehicle (UAV) oblique photography technology is widely utilized in various fields owing to such advantages as true three-dimensional (3D), high precision, and low expenses. We explored the application of UAV oblique photography in the superposed fold analysis conducted in the Xuhuai region. Three feasible and time-efficient steps were established to fulfil the task. The tile images from UAV oblique photography are first synthesized on the Altizure website into a 3D outcrop model, which is then imported into ArcScene to extract bedding and lineation attitudes by GeoAnalysis Tools. The fold geometry and superposed style were characterized and analysed based on the 3D model, followed by extending the 3D structure morphology across the entire outcrop scale and illustrating the superposition style and sequence in the GOCAD platform. The geological conclusions were drawn by applying the method for analysing two outcrops in the Xuhuai region. Two phases of folds were identified, with the first generation nearly E-W-trending oblique-recumbent folds overprinted by the second-generation NNE-NE-trending wide and upright folds. The nearly E-W-striking fold is inferred to be related to the compressive orogeny in the Dabie Orogenic Belt in the Triassic. The NNE-NE-striking fold is related to the northwest subduction of the Pacific Plate or the northward thrust of the Sulu Orogenic Belt in the Jurassic. This example demonstrates that UAV oblique photography is a powerful and reliable method for structural analysis at the outcrop scale, especially for the inaccessible outcrops with weak vegetation cover.

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