“The sea, washing the equator and the poles, offers its perilous aid, and the power and empire that follow it. . . . ‘Beware of me,’ it says, ‘but if you can hold me, I am the key to all the lands." ~ Ralph Waldo Emerson
The most destructive waves ever to hit Hawai`i arrived on April Fool's Day 1946.
Triggered by a 7.1 level earthquake in the Aleutian Islands off Alaska, a
tsunami broke over the north and east shores of the Islands, hitting the town of
Hilo especially hard. Maximum wave run-ups of 55 feet were recorded in Pololu
valley on Hawai`i island. In some places, sea water came half a mile inland.
Before the first waves, the ocean was drawn out from shore up to 500 feet.
Hilo Bay 1946
Tsunamis are primarily associated with the occurrence of earthquakes in oceanic
and coastal regions. When an earthquake occurs, the energy generated travels
outward in all directions from the source. This can be illustrated by throwing a
pebble into a small, still pond. The pebble represents a meteorite or some other
energy source, and the pond represents the ocean. The ripples that travel out in
all directions from the focus, or the point where the pebble hit the water,
represent the energy that creates a sea wave or tsunami. Waves become larger as
they reach the shore, where the water is shallower.
Detecting tsunamis
is a very difficult thing to do. When a wave begins in the deep ocean waters, it
may only have a height of about twelve to twenty-three inches and look like
nothing more than the gentle rise and fall of the sea surface.
When a tsunami finally reaches the shore, it may appear as a rapidly rising or
falling tide, or a series of breaking waves. Reefs, bays, entrances to rivers,
undersea features, and the slope of the beach all help to modify the tsunami as
it approaches the shore. Tsunamis rarely become great, towering, breaking waves.
Sometimes the tsunami may break far offshore. On occasion, a tsunami may form a
bore, a step-like wave with a steep breaking front, which can happen if the
tsunami moves from deep water into a shallow bay or river.
The first
wave may not be the largest in the series of waves. One coastal area may see no
damaging wave activity, while in another area, destructive waves can be large
and violent. The flooding of an area can extend inland by 1,000 feet (305
meters) or more, covering large expanses of land with water and debris. Flooding
tsunami waves tend to carry loose objects and people out to sea when they
retreat.
The tsunami of 1946 was generated by a magnitude 7.1 earthquake in the
Aleutian Islands. This tsunami struck the Big Island of Hawaii on April 1st. The
tsunami flooded the downtown area of Hilo killing 159 people and causing more
than $26 million in damages.
The tsunami of May 23, 1960 was generated by a magnitude 8.3 earthquake in Chile. The 35 foot tsunami struck Hilo, Hawaii causing severe damage. 61 deaths were recorded and $23 million in damage occurred. In the area of maximum destruction, only buildings of reinforced concrete or structural steel, and a few others sheltered by these buildings, remained standing - and even these were generally gutted. Frame buildings were either crushed or floated nearly to the limits of the flooding.
Hilo, Hawaii 1960
All Images: Pacific Tsunami Museum Archives
