120 
PACIFIC SCIENCE, Vol. XXI, January 1967 
01 2 3 4 5 KILOMETERS 
Fig. 1 . Locations and elevations, in meters, of U. S. Geological Survey seismometers ( circles ) on Kilauea 
and a constructed sonic wave front based on data picked up by the seismometers. 
turbances, thus eliminating Mauna Loa as a 
source. Gunfire from the U. S. Army base at 
Pohakuloa, which is often heard by Hilo and 
Volcano residents during training exercises, was 
ruled out as a possible cause when it was 
learned that the base was then inactive. 
INTERPRETATION OF RECORDED DATA 
All four seismometers are timed from the 
same master clock, and accurate comparison of 
events recorded by these instruments is possible. 
Figure 2, a copy of the Desert seismogram, 
shows the disturbances described above, as well 
as those of a few local earthquakes for com- 
parison. As the Desert seismometer seemed to 
be most sensitive to the sonic arrivals, its record 
was used in compiling a master list, which in- 
cludes every suspicious event recorded during 
the disturbed period. The Uwekahuna seismo- , 
graph has a response similar to that of the ! 
Desert, although it is recorded optically. All 
events on the Uwekahuna record are shown in 
Table 1. Records from the Mauna Loa and 
Ahua instruments are similar to those from 
Desert. As stated above, events recorded on 
Desert were recorded on Ahua 17 seconds later. 
The next morning, 20 December 1961, ob- 
servatory personnel noticed renewed activity on 
the Desert record. People in the Hilo area, who 
perhaps were alerted by the events of the pre- 
vious evening, called the observatory, and, as j 
was the case the evening before, reported that j 
they had experienced an audible sensation rather 
than a physical one, and that windows vibrated 
strongly and wall clocks shook. With the expec- 
tation that Mauna Loa should be the first local 
station to record these events, the gain on that 
