ISTANBUL, Turkey (AP) - A strong earthquake struck western Turkey Monday, collapsing buildings already damaged in a deadly quake last month and killing at least six people and injuring more than 200, officials said. Most of the injured suffered broken bones as they jumped from buildings. The 2:55 p.m. quake had a preliminary magnitude of 5.8 and was centered on Izmit, about 50 miles southeast of Istanbul, the city's Kandilli Observatory reported. The U.S. Geological Survey in Golden, Colo., also reported that the quake registered a preliminary magnitude of 5.8, and called it an aftershock to the August quake that killed more than 15,000 people.