UAS-DERIVED CLOUD POINT ANALYSIS FOR THE 5.8-MAGNITUDE PAWNEE OKLAHOMA EARTHQUAKE

Unmanned aerial systems (UAS) provides a synoptic framework for understanding the geophysical phenomena underlying natural hazards. This work describes current UAS and structure from motion (SfM) technologies and the experience to use them for geo-hazards analysis, using the Oklahoma earthquakes as a case study. The objectives of this work is to determine from observational and statistical data analysis the geomorphologic impact and subsequent trends that can be inferred from earthquake events and to analyze the potentially detectable deformation expressed on the surface geology for terrain analysis. To approach these objectives, an Unmanned Aerial Survey was conducted for a 500 square meter area at the location of 2016 5.8-magnitude Pawnee earthquake, Oklahoma. A DJI Phantom IV Pro aircraft equipped with typical autopilot features were combined with on-board inertial measurement unit, a global positioning system unit, and flight control unit to achieve JPEG file type 4864 x 3648-pixel images. At 9 millimeters focal length, a complementary metal-oxide-semiconductor (CMOS) image sensor size of 1 inch, producing an effective pixel of 20M, the mission delivered an overlap of 80% forward and 60% side. Due to daylight variation a max aperture of 2.97 was considered for two camera orientations nadir and oblique (30 degrees from nadir) to improve the resolution of elevation for vertical displacement. The images acquired during the mission flight were processed to acquire a digital elevation model to compare with the lidar cloud points. The data acquired has been used to analyze for detectable deformation expressed on the surface geology aimed at identifying the potential for geologic hazards. USGS seismic data was used to constrain interpretation and the analysis showed areas of steep vertical subsidence with conjugate patterns and subsidence of up to 50 cm change. Frequency of distribution of depth of epicenter showing the mean depth at 5.22km and the modal is 5.0km indicating a zone of weakness or fault bearing lithology around the modal depth. A 100m radial projection of zone energy dispersion showed overlapping zones of energy amplification thus leading to the strongest injection well-induced earthquake experienced in the history of the state.