August 16, 1976 Tsunami: Moro Gulf, Philippines

5,000 to 8,000 reported killed and 90,000 left homeless by earthquake and tsunami. Extensive damage along coastal areas of Moro Gulf. Tsunami heights (in meters above normal sea level) were: 4.3 at Letayen, Bongo island, and Pagadian City, 3.4 at Lebak, and 3 at Sacol Island. Seiche generated in Lake Sebu. (Reference #1053)

As a result of the earthquake and tsunami over 8,000 persons were killed or missing. 10,000 were injured, and 90,000 were left homeless. Based on the investigation of the affected regions it was concluded that the maximum waves in Moro Gulf reached a height of 4-4.8 m which was much lower than what was reported by the press. Large waves were also observed at heights of 4.3 m in Alicia, Pagadian, and on Bongo Island; 3.4 m on Lebak, and at 3 m on Resa Bay, the eastern coast of Basilan and the Jolo Islands, and on Sacol Island. In Lake Cebu, seiches (standing waves) appeared. A tsunami with a maximum amplitude of 35 cm was recorded by tide gauges in Davao. (reference #417)

A newspaper report stated that the "Office of Civil Defense recorded five tsunamis and a series of big waves triggered by the quake. A total of 1,440 peopled died in Zamboanga del Sur, 7,701 people were injured and 909 were reported missing and believed to have drowned at sea. Most of the fatalities were residents of the coastal villages of Pagadian. A total of 49,848 people lost their homes. Of the 11 coastal villages in Pagadian, Santa Lucia was the hardest hit because it was more populated and several communities are situated in the mangrove areas. Mondarte [Santa Lucia barangay chair was then an engineering graduate] remembered that when the waves subsided, hundreds of bodies littered the village. Houses were destroyed and uprooted, while mud was all over." (reference #2546)

Tsunamis due to the August 17, 1976 earthquake in the Mindanao area reportedly reached heights of 4.6 to 6. 1 m and went as far inland as 1 km. Tsunami waves were responsible for 85% of the deaths [3564] and 65% of the injuries [8256] in this disaster (see Table 3). Of those thought missing [1502], 95% were associated with the tsunami. (reference #3670)

Rushing to the shore, the giant waves reached Pagadian, 178 kms away in just 18.4 minutes; struck Sacol Island near Zamboanga City, 225 kms away, in 23.3 minutes; and washed the Basilan coast, 200 kms away in 20.7 minutes. There was therefore very little time to warn the coast dwellers of the Moro Gulf of the approach of the tsunamis. (reference #1187)

Moro Gulf 4 -5m. 8,000 reported killed. Many houses destroyed and washed away. Tsunami reached Japan. (reference #150)

A large tsunami generated by the earthquake resulted in the death of thousands of people in coastal communities

in the Sulu Islands and North and South Zamboanga, North and South Lanao, North Cotabato, Maguindanao, and Sultan Kudarat, and on the island of Mindanao. (reference #4171)

Acharya (1978), citing a PAGASA report, gave the number of deaths as 4000 while Badillo and Astilla (1978) estimated deaths to be about 8,000. The resulting tsunami is considered as one of the most destructive tsunamis in the Philippine earthquake history. Eighty-five percent of the casualties may be attributed to tsunami. It might have been as high as nine meters in the town of Lebak in Sultan Kudarat. Most accounts mentioned three to four distinct waves, the earliest wave arrived around five minutes after the intense shaking. For those who witnessed the tsunami, it was preceded by a very noticeable drop in sea level. It inundated almost all coastal towns of provinces bordering Moro Gulf such as Zamboanga del Sur, Lanao del Norte, Cotabato, Sultan

Kudarat, Maguindanao, Sulu, Tawi-tawi and Basilan. (reference #10958)