August 21, 1902 Earthquake: Lanao, Cotabato, Mindanao, Philippines

1902, August 21, 19:17 [local time], 7.5 N, 123.5 E, magnitude 7.25. There was an earthquake with a maximal intensity of 9 degrees (X Rossi-Forel) on the south of Mindanao Island, in the provinces of Lanao and Cotabato. Its source was situated in the northern part of Illana Bay. Heavy losses were inflicted on all the buildings in the cities, to the fortresses as well as the settlements of the Moro tribe, situated in the pleistoseismic zone. Unusual effects were observed on land as well as in the bay. In particular, the underwater telegraph, cable in the bay was cut and washed out. There were rather reliable reports about numerous victims at the fortifications of the Moro tribe, but the exact number is unknown. The zone of perceptibility included the islands in the Visayan Sea and measured 700 x 680 km. An underground rumble was heard for an enormous distance. There were so many recurrent shocks that about 400 were counted in only the first eight days after the catastrophe, and 10-12 of them reached 5-6 degrees (VI-VII). The main earthquake was registered by European seismic stations. Sieberg, in relating this information, adds that a tsunami occurred. There is thus no reliable information about a tsunami, although one cannot entirely eliminate the possibility. (reference #414)

1902, August 21, 19:17 [local time], Intensity X. Southwestern Mindanao. Destructive earthquake in the Lanao and Cotabato districts. It proceeded from the center which lies in the northern part of Illana Bay, and caused heavy damage to all the buildings in the towns and in the Moro villages and strongholds within the meizoseismal region. The effects were extraordinary on land as well as within the bay; in the latter the telegraph cables were found broken and buried by debris. It is assumed as certain that there were many lives lost in the Moro forts, but their number is not known. The aftershocks were so frequent that some 400 could be counted within the first 8 days after the disaster, some 10 or 12 of these reaching force VI and and VII. (reference #1072)

1902, August 21, 7:17 p.m. 8.1 N, 124.25 E, intensity X. Mindanao: Laguna de Lanao - a very violent earthquake. Houses were thrown down, fissures were opened in the earth. (reference #1187)

1902, August 21. Lanao and Cotabato, intensity X, 12 deaths, very destructive. (reference #1058)