A strong earthquake shook central Indonesia on Tuesday, causing tall buildings in the capital to sway and briefly prompting a tsunami alert, authorities and witnesses said. The Indonesian Meteorological and Geophysics Agency issued a tsunami alert, but there were no immediate signs of large waves and the alert was revoked within 30 minutes. The quake with a preliminary magnitude of 6.6 struck at a depth of roughly 20 km in the Sunda Strait, about 250 km northeast of Jakarta, Indonesian officials said.