ATHENS, Greece (AP) - A strong earthquake shook northwestern Greece Wednesday, but there were no immediate reports of damages or injuries. The quake, with a preliminary magnitude of 5, was centered 200 miles northwest of Athens between the towns of Ioannina and Igoumenitsa, the Athens Geodynamic Institute said. A quake of magnitude 2.5 to 3 is the smallest generally felt by people. A quake of magnitude 4 often causes slight damage. Magnitude 5 can produce moderate damage.