JAKARTA — A magnitude 6.1 earthquake struck off the Indonesian island of Sumatra on Tuesday, according to the US Geological Survey, with no immediate reports of casualties or damage and no tsunami alert. The temblor hit off the island’s west coast and was felt as far away as North Sumatra, authorities said, prompting people to flee outdoors in a region accustomed to devastating earth tremors. /dl READ: Indonesia residents rush outside as 6.6M quake hits... Keep on reading: Strong quake hits off Indonesia's Sumatra island – USGS