More than three dozen people were injured when a wood platform holding live fireworks tipped over, sending the pyrotechnics into a crowd at an Independence Day show outside Los Angeles, authorities said Friday. Between 8,000 and 10,000 revelers were settling into their seats for the fireworks extravaganza at a Simi Valley park Thursday night when the spectacle of lights that were supposed to be launched in the sky never took off. Instead, a bright plume of red and white bursts spread across the ground, sending onlookers fleeing for safety. Thirty-nine people were injured. The victims, from 17 months to 78 years old, had burns and shrapnel wounds, and some were trampled, authorities and hospital officials said. The injured included 12 children.