Surface-wave characterization of the SHOAL nuclear blast cavity and rubble chimney

In 1963 the 15 kT SHOAL nuclear detonation east of Fallon, NV blasted a cavity 25 m in radius at 400 m depth in hard granite. A few months after the blast, drilling found the top of the rubble collapse chimney at 250 m depth. The 2018 Applied Geophysics course at the University of Nevada, Reno will conduct geophysical surveys over the SHOAL ground zero to attempt to identify the blast cavity and rubble chimney with gravity, magnetic, seismic reflection, shallow ReMi, and deep ReMi surveys. The main question is whether the top of the collapse chimney is evident in any of the surveys. Thirty PASSCAL Texans with 4.5Hz geophones will record 4 hours of passive microtremor noise on 3 km arrays centered on SHOAL ground zero. An active-source deep ReMi experiment detailed the 600-m-deep low-velocity body interpreted to be the collapse chimney at the SALUT test site at NNSS. Passive deep ReMi surveys have determined shear-velocity structure to 1 km depth in the Reno basin (Pancha er al., Dec. 2017 BSSA). The SHOAL site is much quietly than urban Reno, except for US Navy “Top Gun” training activities. The SHOAL ground zero area is entirely open and accessible.