Three strong earthquakes occurred Saturday 270 kilometers (about 165 miles) southwest of Athens without causing any casualties or serious damage, authorities said. The first earthquake, of 5.4 magnitude, occurred at 0857 local time (0557 GMT). The second, a magnitude 5.9 quake occurred at 1436 local (1136 GMT). A third earthquake, of magnitude 5.0. occurred at 1645 local (1345 GMT), the Athens Geodynamic Institute said. The earthquakes had the same epicenter, a point at sea south of the southwestern tip of the Peloponnese. The area has produced several strong earthquakes in the past. Greece lies in one of the most earthquake-prone regions of the world.