ABSTRACT Ground motion produced by Mike shot of Operation Ivy (Project 6.5) was measured as three components of acceleration at four ground ranges between 8000 and 114,000 ft. Gauges were in sand below the water table at depths of about 17 ft. Similar measurements were made ona massive concrete instrument shelter at about 30,000 ft from Ground Zero. A rough empirical relation was derived for scaled peak ground-transmitted acceleration as a function of scaled ground range and compared with similar data from Operation Green- house. The peak vertical acceleration produced by incidence of the air shock in the vicinity of the gauge station was related empirically to the peak air overpressure. These relations are necessarily rough because of the few reliable data available, but are probably adequate for es- timating effects of megaton weapon bursts. The acceleration data were converted to velocitytime and displacement-time information. _ — Ground-motion data derived trom shot d . ; jot Operation Castle (Project 1.7) are presented in Chap. 2. These data, because oftffé low yield of the shot, are inadequate for correlation with the results of other tests. Procedures employed for correction of acceleration data integrated to velocities and displacements are discussed in Appendix B.