MANILA, Philippines (AP) - A moderately strong earthquake shook a wide area of the central and southern Philippines Thursday, but authorities reported no serious damage or injuries. The earthquake, with a preliminary magnitude of 6, was centered under the sea near Siargao and Dinagat islands, 440 miles southeast of Manila. The quake triggered no ocean waves, called tsunami, but aftershocks were expected, said seismologist Janjan de Ocampo of the Philippine Institute of Volcanology and Seismology. No aftershocks had been reported nearly four hours after the earthquake struck at 9:20 a.m.