An Unusual Example of Pseudoseisms 1 Resulting 
from Military Exercises 2 
Harold L„ Krivoy, Charles G. Johnson, and Robert Y. Koyanagi 3 
ABSTRACT: Aerial bombing of the target island of Kahoolawe, Hawaii, during 
several hours on 19 and 20 December 1961 and on 13 February 1962 generated 
acoustic disturbances that were felt by people and recorded by seismometers on the 
island of Hawaii. The azimuth of arrival of the pseudoseisms was calculated from 
the accurate seismographic responses. Special atmospheric conditions are suspected 
as prime agencies in the propagation and focusing of these phenomena; lack of 
specific data in this field, however, leaves 
lative. 
Many communities have been disturbed by 
sonic booms created by high-speed aircraft. 
This problem has not yet become serious on 
the island of Hawaii, which has only recently 
established jet facilities. Nonetheless, series of 
disturbances resembling sonic booms were felt 
and recorded on Hawaii during several hours 
of the evening of 19 December 1961, the 
morning of 20 December 1961, and the evening 
of 13 February 1962. Since the affected neigh- 
borhoods are in a zone of active volcanism, 
prompt differentiation between artificial and 
natural events is a problem of immediate con- 
cern to the population and to the authorities. 
From the results presented here, it seems 
possible that careful study of the character and 
timing of sonic disturbances recorded on 
Hawaiian seismographs by experienced seismol- 
ogists may permit prompt identification of the 
source. Other experiments under more con- 
trolled conditions have already revealed im- 
portant facts about energy distribution, refrac- 
tion paths, etc. between the source and the 
receptors. 
EVENTS LEADING TO THIS STUDY 
Between 19:00 and 20:00 (hst) on 19 
December 1961, an unusual variety of sensa- 
1 This term is used in Gutenberg and Richter’s 
published description (1931) of a similar incident. 
2 Publication authorized by the Director, U. S. Geo- 
logical Survey. 
3 U. S. Geological Survey, Flagstaff, Arizona, Den- 
ver, Colorado, and Hawaiian Volcano Observatory, 
Hawaii, respectively. 
the matter of atmospheric structure specu- 
tions were both felt and recorded on the island 
of Hawaii. Personnel of the U. S. Geological 
Survey’s Hawaiian Volcano Observatory at 
Hawaii Volcanoes National Park, who were at 
their homes about 3 miles from the observatory, 
were aware of explosive shocks. When they 
reached the observatory they inspected the 
recordings being written by the high-gain, 
short-period, vertical seismographs at Desert, 
Uwekahuna, Ahua, and Mauna Loa stations. 
They recognized that the "pattern” of data as 
written by the Desert seismograph had been 
repeated by the Ahua seismograph after a lapse 
of about 17 seconds. (See Fig. 1 for station 
locations.) The observatory personnel assumed 
that these were sonic disturbances, and that they 
were not seismic events which would have swept 
the 15 -km net in less than 2 seconds. At about 
the time the shocks were felt in the National 
Park area they were also felt by residents in 
the communities of Volcano, Hilo, and Kau- 
mana. Civil Defense officials, alerted by many 
reports, called the observatory and were advised 
of the results of the seismogram analysis. 
During the evening, all possible local noise 
sources were checked carefully. Explosive vol- 
canism, though rare at Hawaiian volcanoes, is 
always a possibility. In this case, the lack of 
reports from Kona seemed to rule out eruption 
of the dormant volcano Hualalai. A radio check 
with personnel at the U. S. Weather Bureau, 
Mauna Loa Slope Observatory, 6 miles from the 
summit caldera of Mauna Loa, indicated that 
no one there had felt, heard, or sensed the dis- 
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