WEST, Tex. — The blast was so powerful that the United States Geological Survey registered it as a 2.1-magnitude earthquake. It reduced an apartment complex to a charred skeleton, leveled homes in a five-block radius and burned with such intensity that railroad tracks were fused. It killed up to 15 people and injured up to 180. Volunteer firefighters were missing. Residents of a nursing home were pulled from debris and rushed to hospitals