EVIDENCE FOR LARGE TSUNAMI IN THE TONGAN ISLANDS
A tsunami with a 2.5-meter run-up has previously been reported for the Haapai Islands after the April 30, 1919 (Ms 8.0) earthquake. The epicenter was about 160 kilometers east of Vavau in the Tongan Trench. A written account of this tsunami reaching Otualea Beach, Vavau has been recently discovered in the personal history of a Tongan who was there in 1919. According to his story, a large tidal wave struck the shoreline east of Haalaufuli and climbed nearly half way up the cliff while fish, sharks, and sea life of all kinds were thrown on the tree tops. From his description, it appears as though the run-up could have been as high as 20 meters or more. A small village of beach houses was destroyed, but no one was killed or injured. The earthquake that created this tsunami may have also generated a submarine landslide on the southwest flank of the nearby Capricorn seamount. Another large wave has been reported on the island of Eua that occurred around 1959. This wave washed a large boat ashore at Ohonua.
Further evidence for large tsunami may exist where large boulders have been deposited on land. Two such boulders exist on Tafahi; others are on Vavau, Haapai and Tongatapu. The largest one examined was found near the town of Fahefa on the southwest side of Tongatapu. It is a well-rounded limestone boulder about 15 meters in diameter and weighing about 2,500 tons. There are at least 9 other smaller boulders sitting on the ground in the town of Haveluliku on the east side of the island. They are of special interest as they are located about 25 meters above sea level and about 450 meters from the shoreline.