**Tsunamis: A Historical Perspective**

**Introduction:**

Tsunamis have occurred throughout human history. The explosive eruption
of the volcanic Island of Santorini in the Aegean Sea in approximately
1500 B.C.E. generated a tsunami that swept the shores of nearby islands
and helped lead to the end of the Minoan culture. Not incidentally,
there are some who feel this event was the basis of the myth of
Atlantis.

Since the eruption of Santorini, humankind has been afflicted with
tsunamis in all oceans and on all inhabited continents. Although the
Pacific Ocean is known for numerous tsunamis, significant numbers have
occurred in the Mediterranean Sea, the Caribbean Sea, and the area
surrounding the Indonesian archipelago. Although less common in the
Atlantic Ocean, one of the great natural disasters of European history
occurred on November 1, 1755, when a great earthquake with follow-on
tsunamis between 15 and 40 feet high devastated much of the Spanish and
Portuguese coasts. Lisbon, in particular, experienced catastrophic
damage and it is believed that tens of thousands perished as the result
of the earthquake and tsunamis.

Although tsunami waves were noted at many Caribbean Islands following
the Lisbon earthquake, little notice was made in the British colonies of
North America. There was no infrastructure to observe the small water
level fluctuations that would have been superimposed upon normal tidal
observations from New England to Georgia. It would not be until after
the American Revolution that the scientific infrastructure grew up that
could observe and analyze such natural phenomena. Ancestor agencies of
today's NOAA were instrumental in developing these capabilities. First
among those was the Survey of the Coast, known later as the Coast Survey
and then Coast and Geodetic Survey.

The American scientific infrastructure as we know it today had its
beginnings with the authorization of a Survey of the Coast during the
administration of President Thomas Jefferson in 1807. From small
beginnings, this first agency of the Federal Government had grown into a
robust organization by the 1850's conducting survey operations along all
coastlines of the growing United States.

**Serendipitous Science**

Within the instrument shop of the United States Coast Survey, a new
technology called a self-registering tide gauge was developed. In 1854
three of these new instruments were shipped to the West Coast of the
United States for installation at San Diego, San Francisco, and Astoria.
Lieutenant William P. Trowbridge, United States Army, was tasked with
installing these gages and assuring their proper operation.

Within six months of the installation of the San Francisco gauge, a
major earthquake occurred on December 23, 1854, near the central coast
of Japan raising a series of great tsunamis along portions of the
Japanese coast. The tsunamis traveled across the Pacific Ocean and were
recorded as attenuated waves on the self-registering tide gauges along
the western coast. These waves were superimposed upon the regular tidal
record as a series of sinusoidal squiggles. The first person to
recognize the significance of these squiggles was Lieutenant Trowbridge
who wrote to Superintendent Bache in early 1855, "There is every reason
to presume that the effect was caused by a sub-marine earthquake." This
was an amazing insight given that recording seismographs were still
twenty-five years in the future and that no earthquake or tsunami had
ever been remotely sensed by any means up to this time.

Trowbridge's insight was validated when word of a major earthquake
occurring on the coast of Japan on December 23 reached Superintendent
Bache. Armed with knowledge of the time of the earthquake, its location,
times of arrival of the tsunami waves at both San Francisco and San
Diego (from the tide gauge records), and times between crests of the
various waves, Superintendent Bache was able to estimate the average
depth of the Pacific Ocean. Bache was familiar with the latest basic
research published by Sir George Biddell Airy and his treatise on Waves
and Tides in the Encyclopaedia Metropolitana in 1849. Airy had
mathematically developed theoretical expressions that govern the motion
of waves in canals of uniform depth and compiled tables for expressing
the relationships between wave length, wave period, wave velocity and
depth of water. Bache interpolated the Airy table values using his
distance estimates and the tide gauge measurements for the theoretical
tsunami wave travel lines between Shimoda, Japan and both San Diego and
San Francisco. Using two separate estimates for the times of the
disturbance due to the tsunami on the tide gauge curve at San Francisco,
Bache estimated the average depth of the Pacific between Shimoda and San
Francisco to be 13,380 feet and 15,000 feet. For the line between
Shimoda and San Diego, the average depth was estimated to be 12,600
feet. Considering that these were estimates of the average depth of the
Pacific Ocean using indirect measurement and theoretical relationships
of waves for canals of uniform depth, these numbers agree remarkably
well with published values based upon modern measurement technology.
Modern day estimates for the average depth for the depth profile from
Shimoda to San Francisco are 15,504 feet and 15,221 feet from Shimoda to
San Diego. Bache published his estimates at a time when deep sea
sounding technology was in its infancy, inaccurate soundings ranging
between 30,000 to 50,000 feet were fairly common, and there was great
uncertainty concerning the true average depth of the oceans.

Over the ensuing years, Coast Survey and then Coast and Geodetic Survey
(as the organization became known after 1878) tide gauges observed many
of the great tsunamogenic events of the Indo-Pacific region. In
particular, remnants of the great Krakatoa tsunami, caused by the
eruption and near-instantaneous destruction of the island of Krakatoa,
was observed prior to any notification of this great disaster in the
United States. The Coast and Geodetic Survey announced word of a
potentially great disaster prior to receiving the particulars via
telegraph and news media of the time.

**Beginnings of Modern Seismology**

In spite of the ability to observe the remnants of great tsunamis on
tide records, there was still no infrastructure or mechanism in place to
warn of impending tsunamis. The science of seismology was not even in
its infancy until late in the Nineteenth Century when three British
scientists traveled to Japan to observe and study earthquakes and their
attendant phenomena between 1878 and 1883. John Milne invented the first
accurate seismograph and with his colleagues, Thomas Gray and James
Alfred Ewing, made many contributions to the early development of
seismology. Thomas Corwin Mendenhall, a professor of physics and future
Superintendent of the Coast and Geodetic Survey, was active in Japan in
seismology and geophysics during the same period.

In the United States, weather service field offices had absorbed the
task of recording observed (felt) earthquakes almost since the beginning
of a national weather network. Initially these reports were anecdotal
accounts of observations and subjective measures of intensity and
damage. The first account of tsunami damage on United States soil was
published in the Monthly Weather Review for October 1878 and reported
that on August 29, 1878, an earthquake and accompanying tidal wave
destroyed the village of Makuslin on Unalaska Island in the eastern
Aleutians.

Although the Weather Service had been tasked with conducting
seismological observations, the Coast and Geodetic Survey maintained
seismographs at all of its geomagnetic observatories. Because of this,
and its related earth science activities of geodesy, oceanography, and
gravity studies, the Survey was designated the primary seismological
agency of the United States Government in 1925. Over the next twenty
years instrumental improvements were made, engineering seismology
related to studies of man-made structures evolved within the Survey, and
improvements were made in methods of data analysis and dissemination.
There was even sufficient information for Captain Nicholas Heck, Chief
of the Division of Terrestrial Magnetism and Seismology, to compile a
list of over 200 destructive tsunamis that he presented at a meeting of
the International Union of Geodesy and Geophysics in 1934. However,
although there had been tsunamis in Alaska, Puerto Rico, and the
Philippines (a United States territory until 1946) during these years,
little notice had been made of them other than locally. This all changed
on April 1, 1946.

**Genesis of a Tsunami Warning System**

On April 1, 1946, an earthquake occurred south of the Aleutian Islands
generating tsunami waves that devastated Hilo, Hawaii, a little less
than 5 hours later. 159 people were killed in this disaster. This served
as a wakeup call for the United States and led directly to the
establishment of a tsunami warning system by the Coast and Geodetic
Survey. Commander Charles K. Green, an officer in the commissioned
service of the Coast and Geodetic Survey, analyzed tidal records
associated with the tsunami, computed theoretical travel times for
arrival at various locations throughout the Pacific Ocean, and compared
these results to the observed travel times as determined on tidal
records.

Commander Green noticed that on virtually all marigrams (tidal records)
that recorded the tsunami, that there was a small run-up of water level
followed by a relatively large withdrawal over an interval of ten to
twenty minutes. Larger amplitude waves of similar period would follow
this initial indicator. Making use of these facts, Green designed a
system that filtered out short period wind waves and other short-period
oscillations that could affect water level observations. Longer period
waves associated with tsunamis would trigger an alarm when detected.

Commander Green's invention was but one element of a warning system. The
complete warning system that was operational by 1949 included: 1) a
network of four Coast and Geodetic Survey seismograph stations coupled
with two cooperating stations for rapid earthquake epicenter location
determination; 2) a network of tide gauges installed throughout the
Pacific Ocean, some of which had Green's tsunami detection system
installed; 3) an improved seismic sea-wave travel time chart for
determining probable time of tsunami arrival at various locations; and
4) a high-priority communications system that utilized both civil and
military emergency capabilities. This first warning system was devised
only for the Hawaiian Islands; but by March 1964, at the time of the
great Alaska earthquake, the warning area consisted of the entire
Pacific basin from Japan to Chile and from British Columbia to New
Zealand.

**Epilogue**

The Pacific tsunami warning system of today is the direct descendant of
that first system built by the Coast and Geodetic Survey. It is fitting
that the system is operated by the National Oceanic and Atmospheric
Administration, an organization that has many components descended from
the former Coast and Geodetic Survey and the Weather Bureau. Today the
work of the early scientists and engineers of those agencies serves as
the foundation for a tsunami warning system that will become world-wide
in the wake of the great Indian Ocean tsunami event that occurred
December 26, 2004.

**Bibliography:**

Bache, A.D. Notice of Earthquake Waves on the Western Coast of the U.S.,
December 23 and 25, 1854; ocean depth" in Appendix No. 51, Report of the
Superintendent of the Coast Survey .... 1855. Pp. 342-346. Available
on-line at http://docs.lib.noaa.gov/rescue/cgs/001_pdf/CSC-0004.PDF

Green, Charles K. 1946. "Seismic Sea Wave of April 1, 1946, as Recorded
on Tide Gages" in [Transactions , American Geophysical
Union]{.underline}, Vol. 27, Number IV, August 1946. Pp. 490-500.

Heck, Nicholas H. 1934. "List of Seismic Sea Waves" in [Annales de la
Commission pour l'Etude des Raz de Maree]{.underline} , International
Geodetic and Geophysical Union.

[Monthly Weather Review]{.underline} 1878-1925. Numerous mentions of
earthquake observations; a few mentions of tsunamogenic events.

Roberts, E. B. 1950. "A Seismic Sea Wave Warning for the Pacific" in
[The Journal Coast and Geodetic Survey]{.underline}, No. 3. Pp. 74-79.

Sammons, Jack C. 1950. "Destructive Seismic Sea Waves in the Hawaiian
Islands" in [The Journal Coast and Geodetic Survey]{.underline}, No. 3.
Pp. 64-73.

Theberge, Albert E. 2004. "150 Years of Tides on the Western Coast"
presented at celebratory dedication of San Francisco Tide Gauge on June
30, 2004. 15 pp. Available on-line at
<http://tidesandcurrents.noaa.gov/publications/150_years_of_tides.pdf> .

Zerbe, W. B. 1948. "A Seismic Sea Wave Detector" in [The Journal Coast
and Geodetic Survey]{.underline}, No. 1. Pp. 51-55.

Zetler, Bernad D. 1948. "A Seismic Sea Wave Travel Time Chart" in [The
Journal Coast and Geodetic Survey]{.underline}, No. 1. Pp. 56-58.

**Historical Perspective NOAA Library Photos**

**Figures to Accompany "Tsunamis: A Historical Perspective "**

![](media/image1.jpeg){width="4.6097222222222225in"
height="4.029861111111111in"}

Tsunami Travel Time from earthquake in the Pacific Ocean to Hawaii

![](media/image2.jpeg){width="4.813194444444444in"
height="5.279861111111111in"}

Travel-time curves

Seismic Sea Waves, April 1, 1946, Honolulu

![](media/image3.jpeg){width="4.929861111111111in" height="4.45in"}

Tide Gauge record at Honolulu, April 1, 1946

![](media/image4.jpeg){width="3.0in" height="2.504861111111111in"}

Tide curves at San Francisco, CA, Kodiak, Al, Honolulu, HI showing
effects of the eruption of Krakatoa, 1883

![](media/image5.jpeg){width="5.99375in" height="4.686111111111111in"}

SF tide record 1854

San Francisco

Dec. 23, 1854

Marigram

![](media/image6.jpeg){width="4.479861111111111in" height="4.95in"}

Japanese Wave

![](media/image7.jpeg){width="4.659722222222222in"
height="6.676388888888889in"}

Coast and Geodetic Survey

Japanese Wave first used in 1965

Department of Commerce

The Story of the Seismic Sea-Wave Warning System