A strong earthquake shook central Indonesia Tuesday, causing tall buildings in the capital to sway and prompting a tsunami alert, authorities and witnesses said. The quake, with a preliminary magnitude of 6.6, struck at a depth of roughly 12 miles (19 kilometers) in the Sunda Strait, about 155 miles northeast of the capital Jakarta, said Fauzi, a government geologist who goes by one name. The Indonesian Meteorological and Geophysics Agency issued a tsunami alert, but there were no immediate signs of large waves, the Associated Press reported.