Pseudoseisms from Military Exercises— Krivoy, Johnson, and Koyanagi 
127 
A plausible hypothetical model is therefore 
considered, and with vastly oversimplified 
parameters. At an ambient temperature of 
20° C, which is given by Blumenstock as the 
winter mean for the Park housing area, sonic 
velocity is 0.345 km/sec. In fact, we observe 
a velocity of 0.37 km/sec for the range south 
and east of the housing area. If all of this excess 
is assumed to be due to incidence angle, it may 
be computed: 
sin a — .345 = 69°, where a is the angle 
between the incident ray and the vertical. 
Energy from Kahoolawe can then be imagined 
to impinge upon the Mauna Loa and Kilauea 
recording range as follows: On the slopes of 
Mauna Loa, wave fronts move downhill and are 
normal to the surface of the ground; on the 
flatter, low-elevation terrain, wave fronts are 
about 20° from the vertical. Such increases in 
the angle of incidence would improve coupling 
between air and ground, and if such improve- 
ment occurs as theorized above, the maximiza- 
tion of available energy and "seismic” mani- 
festations reported by residents would be the 
expected results. 
THE GROSS PROPAGATION PATH 
The many uncertainties discussed for the 
limited region of acoustic recording are clearly 
multiplied in a consideration of the size and 
complexity of the air space through which the 
energy is refracted. At present there are few 
concentrated data which describe atmospheric 
conditions over Hawaii. For example, although 
daily weather observations are made at Hilo, 
these are limited to that place and concern only 
operational altitudes for aircraft. 
Perkins et al. (I960) illustrated many theo- 
retical and actual instances of the focusing of 
sonic energy due to meteorological conditions. 
Their work seemed to involve more limited 
source-to-target distances ; on their computed 
graphs data are restricted to areas having a 
maximum altitude of 10,000 ft and to lateral 
distances of about 100,000 ft. Variables dis- 
cussed in that report were those of temperature 
and wind velocity; the stratification thus pro- 
duced caused favorable refracting conditions 
and, in turn, focusing. Such conditions in 
Hawaii are known only generally, but salient 
features which would be propitious in generat- 
ing the special phenomena we have recorded 
are summarized: 
(1) Wind velocities which increase with al- 
titude in the Hawaii direction from Kahoolawe. 
This condition is prevalent in the winter when 
trade winds (blowing westward) abate and 
counter trade winds blow near the ground. Thus, 
the propagation pattern discussed above would 
be enhanced during the Hawaiian winter and it 
would normally be inoperative during the rest 
of the year. 
(2) High velocity (higher temperature) 
propagation paths which serve to refract energy 
in the Hawaii direction. This condition prevails 
most of the time (Blumenstock, 1961) in the 
form of a sharp temperature inversion overlying 
the Hawaiian area at altitudes between 5,000 
and 7,000 ft. 
(3) Jet streams in a sheath above 40,000 ft, 
the least understood, but an important, feature. 
These jets, which supposedly blow toward the 
east (thus contributing to situation (1), above), 
can make radical changes in direction and can 
attain great velocities. 
Although more accurate information about 
possible zoning or velocity/temperature stratifi- 
cation between Kahoolawe and Kilauea would 
be helpful, it is still possible to come up with 
an approximation suggested by Perkins et al. 
(I960), who suggested a single gradient case. 
This oversimplification would call for Kahoo- 
lawe and Uwekahuna to lie at opposite ends of 
a chord connecting them. The chord, therefore, 
would be 190 km in length. And the circular 
path intersected by this chord would describe 
the simplified refracted energy path. If it is 
further assumed that tangents to this circular 
path at either end make an angle of 20° with 
the (horizontal) chord (i.e., if we interject 
the previously computed angle of incidence), 
a circular path 280 km in radius results. Such a 
path would reach a height of 17 km before 
refracting downward. This suggestion of a 
major refracting condition somewhere near an 
altitude of 55,000 ft is in good agreement with 
available knowledge about the altitude of the 
tropopause over Hawaii (described briefly in 
(3) above). 
