[en] During the period Jan. through Dec. 1975, personnel of the U.S. Geological Survey mapped the surface effects produced by seven underground nuclear tests conducted in Areas 2, 3, 4, and 7, Yucca Flat, Nevada Test Site. Surface effects include such features as pressure ridges, fractures, and explosion-induced movements along previously mapped faults. Four tests yielded collapse sinks and mappable surface effects, two produced only sinks, and one test produced neither a collapse sink nor mappable surface effects