lenticular masses of cemented sand.* The data are insufficient to permit detailed seismic analy- gis, but average depth to basalt is about 3400 ft. Similar data from Easy and! | shots of Operation Greenhouse indicated a constant seismic velocity of about 6900 ft/sec (Ref. 3) but did not include information from sufficiently remote stations to include refraction through basement rock. Table 1.2--GROUND-ACCELERATION AND AIR-OVERPRESSURE DATA Accelerometers Damped Max. Ground range, ft Station number 615.02 650.01 8,250 8,302 611.01 15,900 650.02 18,334 650.03 air overpressure, psi (40) 611.02 21,412 603 30,226 613.01 36,708 4 611.04 650.05 47,574 47,617 2.7 650.06 114,182 114,240 . Set range,| g natural freq., cps Vv 18 165 R T 18 9 162 128 . Max. pos.,*| g Max. neg.,| g 2.35 13.5 150 1.00 0.41 3.8 0.56 50 77 irAir-shock induced Freq.,f cps Max. pos.,*| g Max. neg.,! Z Freq.,f eps 18.6 21,264 612.01 Component Ground-t und-transmitted 12.4 Vv 4 106 0.26 0.20 2.7 1.34 1.50 R 4 102 0.23 0.27 4.0 0.46 0.45 36 T 2 73 0.14 0.11 4.2 0.19 0.37 42 Vv 3 106 0.23 0.18 3.0 0.74 2.1 22(6.3) R T 3 2 Lit 73 0.23 0.12 0.17 0.07 3.3 46 0.71 0.16 0.46 0.33 67(9.4) 67(13) Vv R T 2 2 2 69 65 79 0.16 10.16 0.26 0.15 0.14 0.20 3.4(1.6)| 3.4(1.8)| 4.5(1.7)| 3.67 3.00 0.85 2.90 2.96 0.49 154 lll 128 1.4 0.034 0.020 21 © 21° No record Vv 0.2 40 0.010 0.080; 0.55 *Positive acceleration has the following directions: up, for all vertical components; in (toward Ground Zero), for all radial components; counterclockwise (as seen from above Ground Zero), for all tangential components. . ?tFrequencies enclosed in parentheses are those of apparently secondary importance. Maximum accelerations and acceleration frequencies are compared in Table 1.2. Set ranges in this table refer to the plus-and-minus ranges of linear response to which the end-instrument-recording systems were set. These values were high by factors ranging from 1.7 to 16 except for the accelerometers on the recorder shelter on Bokon,Station 603, which indicated accelerations nearly twice set ranges. Ground-transmitted signals were below set range by factors of 6 to 20, and air-shock induced data indicate that set ranges should have been lower by factors of from 2 to 10. Consequently the factor used to increase the energy fraction directly coupled to the earth because of the low burst height of Mike shot in estimating set range should probably have been about 4 instead of 50. Data from Stations 650.01 and 603 are anomalous because of incompleteness of the record from Station 650.01 and because of measurementof structural response rather than ground motion at Station 603. Peak accelerations quoted for Station 650.06 in Table 1.2 are estimated for first ground-transmitted arrivals and are lower by a factor of 2 than those for the first reflected signals included in Fig. A.11. Ground-transmitted accelerations were analyzed by a logarithmic plot of peak-scaled ac- celerations as a function of scaled ground range (Fig. 1.6). Scaling was according to the expressions 21