The Kona Earthquake of August 21, 1951, 
and Its Aftershocks^ 
Gordon A. Macdonald and Chester K. Wentworth^ 
INTRODUCTION 
At three minutes before one o’clock on 
the morning of August 21, 1951, the south- 
western part of the island of Hawaii was 
shaken by the strongest earthquake recorded 
there since 1868. The earthquake of August 
21 was felt strongly all over the island of 
Hawaii, weakly on the island of Maui, and 
in Honolulu, 180 miles away from its origin. 
Extensive damage resulted in the central Kona 
district, and lesser damage extended all the 
way to Naalehu, about 38 miles from the 
epicenter. The major earthquake was followed 
by a large number of aftershocks which, 
although they did little damage, kept the 
populace of Kona uneasy for several weeks. 
A detailed study of the earthquake was 
immediately undertaken by the staff of the 
Hawaiian Volcano Observatory. No sharp 
division of labors existed, but for the most 
part Macdonald was responsible for the gen- 
eral and instrumental phases of the investi- 
gation and Wentworth for the detailed studies 
of damage, such as that affecting water tanks, 
stone walls, and gravestones. 
Acknowledgements: It is impossible to men- 
tion by name all the persons who aided the 
investigation by contributing observations on 
the earthquake itself and data on resulting 
damage. To all these we extend our sincere 
thanks. Special thanks are due Howard M. 
^ Publication authorized by the Director, U. S. 
Geological Survey. Manuscript received May 7, 1952. 
2 Director and Geologist, respectively, Hawaiian 
Volcano Observatory, Hawaii National Park, Hawaii. 
Tatsuno, seismograph operator at Konawaena 
High School near the epicentral area; Sister 
Mary Theda, seismograph operator at St. 
Joseph’s School in Hilo; Mrs. Alfred E. 
Hansen at Naalehu, Allan P. Johnston of 
Kapapala, and Nancy R. Wallace of Keala- 
kekua, who contributed descriptive reports 
of many of the aftershocks. Roland E. White, 
of the Honolulu Magnetic Observatory, U. 
S. Coast and Geodetic Survey, kindly sent 
copies of the seismograms of the major earth- 
quake as recorded at Barbers Point, on Oahu. 
Commander C. A. George, of the Coast and 
Geodetic Survey, supplied copies of the tide 
gauge records from Honolulu and Hilo har- 
bors, showing the small tsunami that followed 
the earthquake. Many persons supplied in- 
formation on damaged water tanks. Among 
these Mark Sutherland, Principal of Kona- 
waena School, John Iwane, Extension Service, 
University of Hawaii, and Masuoka Nagai, 
of Captain Cook Coffee Company, were es- 
pecially helpful. 
NARRATIVE 
Most residents of the island of Hawaii 
were in bed when the earthquake struck. 
Nearly everyone in the Kona and Kau dis- 
tricts was awakened, and most people rushed 
outdoors. Persons in the area near the epicen- 
ter reported that the initial movement was 
largely up and down, with some swaying in 
an east-west direction, increasing in intensity 
and giving way to what appeared to be a 
vortical motion. Noise during the earthquake 
was intense as doors and windows rattled, 
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