Hawaii: Today in History 4/1 (Tsunamis, photos)
4-1-1946 Tsunamis generated by a quake in Aleutian Trench strike Hilo, Hawaii
One of the most destructive Pacific-wide tsunamis – and the most severe in the Hawaiian islands – was generated by a large earthquake near Unimak in the Aleutian chain of islands of Alaska.
The earthquake occurred on April 1, 1946, at 12:29 GMT. Its epicenter was at 52.8° N, 163.5° W, and its focal depth was shallow at 25 km.
Although the quake was initially assigned a Richter magnitude of 7.2, in later years, the energy it released was reevaluated and a Moment Magnitude (Mw) of 8.6 was assigned. to this event.
This earthquake generated one of the most destructive
Pacific-wide tsunamis of the 20th century. Near the generating area, at Unimak Island, huge tsunami waves reached 35.0 m (more than 100 feet) above sea level and destroyed completely the newly built, U.S. Coast Guard’s Scotch Cap lighthouse. All 5 men of its crew were killed. The lighthouse was a steel-reinforced concrete structure and its base was at about 30 meters above sea level.
Scotch Cap Lighthouse on Unimak Island, Alaska, before and after the April 1, 1946 earthquake and tsunami. (U.S. Coast Guard photographs)
Tsunami waves advancing across Coconut Island, at the Hilo Bay waterfront. (ITIC Archives; Photograph by Ted Lusdy).
The tsunami continued on to the Hawaiian Islands reaching
the north shore of Kauai island first, approximately 4.5 hours after the earthquake, and Hilo, 4.9 hours later.
A bore advances past the railroad bridge at the mouth of the Wailuku River, Hilo Bay, Hawaii. (ITIC archives; Honolulu Advertiser photograph).
There had been no warning to Hawaii as the Tsunami Warning System had not been established, at that time. The tsunami was extremely damaging in all the islands, but it was particularly devastating in the Island of Hawaii.
The town of Hilo on the island of Hawaii was pounded by a series of 6 to 7 large tsunami waves coming in at 15-20 minute intervals. The highest of these waves had a run up height of 8.1 meters above sea level. The damage was extensive. The waves completely destroyed Hilo’s waterfront killing 159 people there. Every house on the main street facing Hilo Bay was ripped off its foundation and was carried across the street smashing against buildings on the other side.
Tsunami waves striking the beach front area at the Puumaile Tuberculosis Hospital area, east of Hilo. Waves of up to 6.1 m high overtopped the breakwater in this area and flooded the lower level of the hospital (ITIC archives; Photograph source Mrs. Harry A. Simms, Sr.)
Another view of the tsunami striking the beach front area in front of the Puumaile Tuberculosis Hospital, in the eastern side of Hilo. (ITIC Archives; Photograph source Mrs. Harry A. Simms, Sr.)
At Pololu Valley, on Hawaii, tsunami waves of over 12.0 m struck a school at Hawaii’s Laupahoehoe Point, and killed a number of childrenand also destroyed a hospital. . Altogether a total 165 people lost their lives from this tsunami. Damage to property was estimated to be over $26 million (1946 dollars).
A tsunami wave advancing past an auto bridge at Wailuku River in Hilo Bay (ITIC Archives; Honolulu Advertiser photograph).
In 1948, and as As a result of this tsunami, the Pacific Tsunami Warning Center was established in Hawaii. This warning system was expanded in later years and became the headquarters of the International Pacific Warning System.
