An 8.2-magnitude aftershock struck off the coast of Indonesia\'s Sumatra island on Wednesday, following a stronger quake that triggered an Indian Ocean-wide tsunami alert. The US Geological Survey said the aftershock struck at 10:43 GMT, 615 km (382 miles) from Banda Aceh. Southeast Asian nations issued tsunami alerts and urged people to move to safety away from coastlines after the initial 8.6-magnitude earthquake struck off Sumatra.