U.S. experts have calculated the riskiest and safest counties in the country for disasters, and Los Angeles is on the shakiest ground. The new National Risk Index by the Federal Emergency Management Agency looks at 18 natural hazards including hurricanes, tornadoes, earthquakes, volcanoes, floods and heat waves. It also considers how many people and how much valuable property are in harm’s way, social factors and how well a community can bounce back from disaster. After Los Angeles, New York, Miami and Philadelphia are high in risk. Loudoun County in Virginia, other Washington D.C. suburbs, areas near Boston and Long Island rank as some of the safest places.