On August 1, 1968 at 20^h19^m21.9^s (GMT), the whole island of Luzon, including some northern islands of Visayas was shaken by an earthquake of magnitude 7.3 (Ms) with focal depth of 36 kms. (USCGS). The epicenter was placed at 16.5^oN, 122.2^oE or about 250 kms. NNE from the City of Manila or 20 kms. in the same direction from the coastal town of Casiguran, Quezon Province.