An earthquake of magnitude 7.5 struck off the cost of the southern Philippines island of Mindanao on Saturday, the European-Mediterranean Seismological Centre (EMSC) said. A tsunami warning has been issued by the US tsunami warning system.An earthquake of magnitude 7.5 struck off the cost of the southern Philippines island of Mindanao on Saturday, the European-Mediterranean Seismological Centre (EMSC) said. A tsunami warning has been issued by the US tsunami warning system.