Differences due to weapon yield ace the results of variation of positive phase duration with respect to tree natural period, i.e., the pericd modulus. Since the pericd modulus for lIOKT is already sufficiently small the reduction in period modulus due to the larger yield (14.5MT) sgoes not lead to a corresponding decrease in dynamic pressure modulus 2 Isodamage curves shown delineate light and heavy damage to broad- leaf tree stands resulting from 15MT and 130KT weap.ns. The criteria for light and heavy damage given in Table 4.1 are based on total length of stems and limbs on the ground, and are estimates of two degrees of damage in impeding movement of military personnel and vehicles. It should be pointed out here that the criteria used in arriving at the two degrees of damage have no experimental basis. The degree of damage to William Isiand and Victor Island Pisonia stands from Shot 1 was considered as heavy. Scaled distances of Willia Island and Victor Island locations from Shot 1 are shown on Fig. 4.2 by symbols "A" and "3," respectively. The damage based on trees damaged on Victor Island Pisonia plot (Fig. 3.2) by Shot 1 was assessed as 65 per cent. The damage consisted of stem and limb breakage with some uprooting. The 65 per cent damage value was consistent with observations of the stand as a whole. TABLE 4.1 - Criteria for Two Degrees of Damage-Broadleaf Stands, Stocking 196 Trees/Acre — = Degree of Damage Trees Damaged : 5 aan eatin eenthene (4) (ft/acre) Light 10 1500 Heavy 60 9000 The degree of damage from Shot 1 to trees on Uncle Island Pisonia plot (Fig. 3.4) was assessed as 30 per cent or light damage. Scaled ground range of this plot is shown by symbol "C" on Fig. 4.2. For Shot 1, ne damage resulted to Uncle Island stand beyond a scaled ground range of 3180 ft. The nearness of light damage and no damage might sug: gest shock attenuation by the stand. However, the area of no damage ecnsisted mostly of palm and small broadleaf trees as contrasted with the light damage region where inherently weaker Pisonia trees predomi~ rated, This change in the Uncle Island stand composition did not permit estimation of the amount of shock attenuation from observations of degree of damage with distance. The degree of damage by Shot 3 to Uncle Island stand as a whole wa: assessed as heavy. Sealed distances of locations illustrated by Figs. 3.5 tnrough 3.9 are sncwn on Fic. 4.2 by symbols "D" to "H," inclusive. The tallied stem treakase of trees on the sample plots, excluding small diameter broadleaf trees, was $8 per cent. According to Tabie <.1, 37AFSsP,UPSHOT-KNOTHOLE, Project 2.19, Fig. 1.3. 43 SECRET -— RESTRICTED DATA