UW-Madison 3D DAS@SURF

A 3D DAS array consisting of 5.5 km of single-mode fiber-optic cable and a set of co-located geophones was deployed in the Sanford Underground Research Facility (SURF) in Lead, South Dakota, USA between January and May 2022. The sensing heart of the DAS array is a specially installed 3.5 km of cable on the 4550-ft depth level and along a ramp system from approximately 4100 ft to 4850 ft below the surface. The ramp is a three-dimensional spiral-like geometry with a diameter of 150 m at a grade of 9 degrees. The array was re-activated in February 2023 to record data during Global DAS Month using a 16-m spatial resolution. The data include one hour of data sampled at 100 Hz for the 156 earthquakes above magnitude 5 as well as continuously at 50 Hz on February 14, 2023.