Indonesian officials warned that the quake might trigger a tsunami for West Sumatra, North Sumatra, and Aceh. Australia’s Bureau of Meteorology issued a marine warning for the distant Cocos and Christmas islands. Strong and dangerous currents are possible. The tremors could be felt in parts of Singapore. Patients at hospitals in Padang were being evacuated. President Joko Widodo was staying overnight at a hotel in Medan in North Sumatra and was safe, palace officials said.Indonesia straddles the so-called ‘Pacific Ring of Fire,’ a highly seismically active zone where neighboring tectonic plates violently clash, resulting in a large number of earthquakes and volcanoes.