August 1, 1968 Tsunami: E. Luzon Island, Philippines

Reference #414:

1968, August 2, 4:20 [local time], 16.5 N, 122.2 E, depth 36 km, magnitude 7.7. There was a destructive earthquake with source off the east coast of Luzon Island. The earthquake caused a tsunami, which was registered by the tide gauges on the Ryukyu Islands and the Japanese Islands with a mean height of 10 + cm (and a maximal height of 30 cm off the capes on the south coast of Japan, which intensified the oscillations.

The records of the special automatic registers on the islands of Enoshima (Miyagi Prefecture) and Oshima (off the Izu Peninsula), barely show the tsunami. At Ishigaki and Naha (Ryukyu Islands), the height of the tsunami was under 15 cm. The envelope of the oscillations has a spindle shape. The front of the tsunami is traced with difficulty. The time of onset of the most intensive oscillations presumably corresponds to the approach of the marginal (shelf) waves (Hatori, 1969 c).

A weak tsunami was registered by the tide gauges of the U.S. Coast and Geodetic Survey on Guam Island with a height of 3 cm, Wake Island (9 cm), at Honolulu (3 cm), Nawiliwili, and on Attu Island (9 cm). (N-L, 1969, vol . 11, No. 2; Coffman, Cloud, 1970).

[USCGS: 1.VIII; 20h19m22S; 16.5 N., 122.2 E.; 36 km; M=7.7.]

Reference #150:

1968, Aug 2, 05:19 [local time], 16.5 N, 122.2 E, depth 36 km, magnitude 7 MS. No evidence of tsunami at Luzon Is. Tsunami reached Japan.

Reference #1187:

Casiguran - it raised tall waves which drowned one fisherman, caused extensive fissures and landslides of

5,000 sq metres. The sea at the western end of the sea-wall in Calauag was observed to go beyond the shore by 20 metres. This was due to a rise in sea level of 1.3 metres. Rise in sea level was similarly noticed in the town of Quezon at the southern tip of Alabat Island.