High Resolution Magnetic Surveying Using an Unoccupied Aerial Vehicle to Constrain Buried Lava Flow Geometry and Eruption History, Crater Flat (NV)

Abstract:

Magnetic surveys map small-scale anomalies in the Earth’s magnetic field using precise instrumentation. From these anomalies we can infer geologic features buried in the shallow subsurface. Magnetic surveying can be time consuming and expensive for both ground based and aerial surveys. While these techniques are still useful new advances in Unoccupied Aerial Vehicles (UAVs) has innovated how we think about data collection. We present here ways in which UAVs can greatly improve both data collection and data resolution. A DJI Matrice 100 and Sensys Mag Drone R3 Fluxgate dual sensor magnetometer were using to complete 215 line kilometers of magnetic survey in 3.5 days. The continuous data collection by the Sensys magnetometer allowed the collection of approximately 3,880,000 data points. A previous ground based magnetic survey collected at this field site collected 60 line kilometers of data over a 2 week period with 25,000 data points. Flight planning software allows the UAV to fly a draped path over the topography at a specified height, being analogous to carrying a sensor at a given height in a ground-based survey. Techniques used to process data are the same as for a traditional ground-based approach, but with a much greater density of data. Crater Flat, NV consists of five Quaternary, .77-.98 Ma, age cinder cone volcanoes that are part of the wider Southwestern Nevada Volcanic Field. We use the magnetic data and our nonlinear inversion code, MagCube-Parallel, to model the geometry of lava flows completely buried in the alluvium. Our data analysis reveals that the lava flow field from Little Cones extends up to 1.5km south. Inversion of the magnetic field allows us to profile the east-west change in flow topography, estimate paleosurface depth and the intensity of magnetization. Our analysis reveals features such as individual lava flow cooling units and flow lobes that provide rich details about the history of the eruptions that were not observed in previous surveys of the same area. Our findings demonstrate that this methodology can resolve similar, if not better, results as traditional methods while providing scientists with a cheaper and quicker alternative to previous non-UAV based field methods.