We deployed dense seismic arrays to image the shallow structure in the injection area of the Brady Hot Springs geothermal site in Nevada. The arrays were composed of 238 5 Hz, three-component nodal instruments and 8,700 m of distributed acoustic sensing (DAS) fiber-optic cable buried in surface trenches plus 400 m installed in a borehole. The geophone array had about 60 m instrument spacing in the target zone, whereas DAS channel separations were about 1 m, with a 10 m averaging (gauge) length. A large vibroseis truck (T-Rex) was operated at 191 locations.

Models with 100 m and 50 m horizontal node spacing were obtained, with vertical node spacing of 10 to 50 m.  I will present our 3D Vp model from the vibroseis nodal and DAS data and a preliminary analysis of shear-wave structure from ambient noise data. I will also present a brief comparison of nodal and DAS data.