High-Resolution Structure-From-Motion Models and Orthophotos of the Southern Sections of the 2019 Mw 7.1 and 6.4 Ridgecrest Earthquakes Surface Ruptures

Abstract Aerial photographs were collected in the days immediately following the 4–5 July 2019 Ridgecrest earthquake sequence (e.g., Barnhart et al., 2019) along the publically accessible sections of the surface ruptures south of California 178. These photos were then used to produce structure-from-motion point cloud models and orthophotos with resolutions varying from ∼1 to 20 cm/pixel. Here, the models are released and initial observations of the nature of the surface ruptures are presented.

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High-Resolution Structure-from-Motion for Quantitative Measurement of Leading-Edge Roughness

Energies ◽

10.3390/en13153916 ◽

2020 ◽

Vol 13 (15) ◽

pp. 3916 ◽

Cited By ~ 1

Author(s):

Mikkel Schou Nielsen ◽

Ivan Nikolov ◽

Emil Krog Kruse ◽

Jørgen Garnæs ◽

Claus Brøndgaard Madsen

Keyword(s):

High Resolution ◽

Wind Turbine ◽

Structure From Motion ◽

Turbine Blades ◽

Leading Edge ◽

Cost Effective ◽

Wind Turbine Blades ◽

Edge Roughness ◽

High Resolution Structure ◽

Resolution Structure

Over time, erosion of the leading edge of wind turbine blades increases the leading-edge roughness (LER). This may reduce the aerodynamic performance of the blade and hence the annual energy production of the wind turbine. As early detection is key for cost-effective maintenance, inspection methods are needed to quantify the LER of the blade. The aim of this proof-of-principle study is to determine whether high-resolution Structure-from-Motion (SfM) has the sufficient resolution and accuracy for quantitative inspection of LER. SfM provides 3D reconstruction of an object geometry using overlapping images of the object acquired with an RGB camera. Using information of the camera positions and orientations, absolute scale of the reconstruction can be achieved. Combined with a UAV platform, SfM has the potential for remote blade inspections with a reduced downtime. The tip of a decommissioned blade with an artificially enhanced erosion was used for the measurements. For validation, replica molding was used to transfer areas-of-interest to the lab for reference measurements using confocal microscopy. The SfM reconstruction resulted in a spatial resolution of 1 mm as well as a sub-mm accuracy in both the RMS surface roughness and the size of topographic features. In conclusion, high-resolution SfM demonstrated a successful quantitative reconstruction of LER.

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QUANTIFYING POST-FIRE HILLSLOPE AND DEBRIS FLOW EROSION IN A STEEP CATCHMENT USING HIGH-RESOLUTION STRUCTURE FROM MOTION

10.1130/abs/2017am-299999 ◽

2017 ◽

Author(s):

Nicholas Ellett ◽

◽

Jennifer L. Pierce ◽

Jaime Goode ◽

Nancy F. Glenn

Keyword(s):

High Resolution ◽

Debris Flow ◽

Structure From Motion ◽

High Resolution Structure ◽

Resolution Structure

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Targeted High-Resolution Structure from Motion Observations over the Mw 6.4 and 7.1 Ruptures of the Ridgecrest Earthquake Sequence

Seismological Research Letters ◽

10.1785/0220190274 ◽

2020 ◽

Vol 91 (4) ◽

pp. 2087-2095 ◽

Cited By ~ 1

Author(s):

Andrea Donnellan ◽

Gregory Lyzenga ◽

Adnan Ansar ◽

Christine Goulet ◽

Jun Wang ◽

...

Keyword(s):

High Resolution ◽

Structure From Motion ◽

Earthquake Sequence ◽

Ground Sample ◽

High Resolution Imagery ◽

Dirt Road ◽

Before And After ◽

High Resolution Structure ◽

Aerial Systems ◽

Conjugate Fault

Abstract We carried out six targeted structure from motion surveys using small uninhabited aerial systems over the Mw 6.4 and 7.1 ruptures of the Ridgecrest earthquake sequence in the first three months after the events. The surveys cover approximately 500 × 500 m areas just south of Highway 178 with an average ground sample distance of 1.5 cm. The first survey took place five days after the Mw 6.4 foreshock on 9 July 2019. The final survey took place on 27 September 2019. The time between surveys increased over time, with the first five surveys taking place in the first month after the earthquake. Comparison of imagery from before and after the Mw 7.1 earthquake shows variation in slip on the main rupture and a small amount of distributed slip across the scene. Cracks can be observed and mapped in the high-resolution imagery, which show en echelon cracking, fault splays, and a northeast-striking conjugate fault at the Mw 7.1 rupture south of Highway 178 and near the dirt road. Initial postseismic results show little fault afterslip, but possible subsidence in the first 7–10 days after the earthquake, followed by uplift.

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