The 1918 Celebes Sea earthquake occurred on August 15 at 12:18 UTC near the Moro Gulf coast of Mindanao.

The southwestern part of Mindanao sits above a geologically young subduction zone, where the section of the Sunda plate that lies beneath the Celebes Sea is subducting beneath the Philippines Mobile Belt along the line of the Cotabato Trench.

[1][6] The earthquake has been associated with rupture along the active east-dipping Cotabato Trench subduction zone beneath Mindanao.

The average slip is estimated to be 4.1 m.[7] This event in the southern Philippines triggered a large tsunami, with a maximum run-up of 7.2 m,[8] which affected the coasts of the Celebes Sea, causing widespread damage.

[9][better source needed] The earthquake caused widespread damage in the coastal parts of southwestern Mindanao, with all houses destroyed around Sarangani Bay.