Twenty-one reed gages were installed for radial (horizontal) and vertical displacement shock spectrum measurements on the Hard Hat event. Thirteen gages were installed in the tunnel liner structures of Project 3.1. Seven gages were installed in the unlined access tunnel floor. One gage was installed on the surface at a radial distance of 1,340 feet from Hard Hat zero point. Damage in the drift nearest the detonation, although expected to be large, was so severe that the drift was not opened and gage recovery at that range was therefore impossible. Fifteen of the 21 gages installed were recovered and of these, 12 yielded usable records. The three gages which yielded no information were damaged by collapse or partial collapse of the tunnel and structures in which they were placed. (Author).