Acceleration-time plots are presented in Figs. A.12 to A.14, each of which includes all components observed at one station. It is evident that, except for data from Station 170.01, the signal-to-noise ratio is so low that identification of any portion of the signal except air-shock induced acceleration is uncertain. Ground-transmitted acceleration signals are definite on the records from Station 170.01. Approximate arrival times and peak accelerations were read from the data, and the results are compiled in Table 2.1. Table 2.1—-ACCELERATION DATA Acceleration Ground-transmitted Station |: number Ground Set range, range, . ft 1 g Coinponent Arrival Max. time, pos., sec g Max. neg., g Air-shock induced Freq., cps Arrival Max. time, pos., sec g Max. neg., g Freq., cps 170.01 2596 33 33 33 v R T 0.31 Q.31 0.96 1.50 0.47 1.27 No record 42 0.63 45 0.65 3.44 2.20 4.10 4.67 90 100 170.03 3650 24 24 9 v R T 0.39 0.40 0.42 0.37 0.13 0.11 0.25 0.35 0.19 1.24 1.23 1,24 [0.23 0.62 0.24 0.55 0.29 0.18 45 170.02 5599 9 3 3 v R T 0.61 0.61 0.61 0.17 0.13 0.10 0.15 0.12 0.10 2.63 2.56 2.61 0.15 [0.51 0.16 0.51 0.25 0.25 38 The graphof arrival times vs ground range, Fig. 2.2, is a two-branched curve in which the ground-transmitted signal is shown to be propagated with a velocity of slightly over 8700 ft/sec and the air-shock induced signal follows the same pattern as air overpressures, being propagated at velocities which decrease with increasing ground range. The time-distance curve for air-shock induced ground motion is a short range extrapolation of the corresponding one for air-overpressure data, since the station of shortest ground range for which overpressure arrival times are available coincides roughly with the most remote ground-acceleration station. Air overpressures were measured as part of Project 1.2 by Ballistic Research Laboratories (BRL)? and by Sandia Laboratory. * arrival times of the close-in BRL data were not observed, but peak overpressure data were adequately precise for correlation with accelerations. However, precision of acceleration data from two stations, 170.03 and 170. 02, was too low to be suitable for correlation, and the results of comparison of peak pressures and accelerations are consequently of little value. They are sufficient simply to indicate that for two stations, 170.03 and 170.02, at overpressures of about 21 and 8.2 psi the air-shock induced vertical accelerations were about 75 and 25 per cent below those predicted by Eq. 1.2 (A = 0.053p'+*) derived from Mike-shotdata. Acceleration. frequencies could be read from the recorded signals with reasonable confidence in only a few cases. These few observations, which are included in Table 2.1, indicate merely that the frequencies of’ _shot data are similar to those observed at the close-in stations during Mike shot. “Noise or other extraneous oscillations obscured the recognizable acceleration frequencies on the records for which no data were included. Analysis in terms of velocities or displacements was not attempted because the ground motion was too small to produce structural damage and precision of the data was too poor to support integration. shot placed the 40-psi ground rangeat Station 170.01. Actual yield of the These data were consequently derived from an overpressure level corresponding approxi - mately to that of Station 650.01 for Mike shot of Operation Ivy and, had they been complete, might have been useful adjuncts to the incomplete Mike-shot data. 33