Earthquakes in the United States

The United States straddles several tectonically active zones, making its western states among the most seismically hazardous in the country. California sits astride the San Andreas Fault, a roughly 1,200-kilometer transform boundary where the Pacific and North American plates grind past one another. Alaska, along the northern edge of the Pacific 'Ring of Fire', is by far the most earthquake-prone state, absorbing subduction stress along the Aleutian Trench.

The 1906 San Francisco earthquake, estimated at magnitude 7.9, ruptured nearly 480 kilometers of the San Andreas Fault and, together with the fires that followed, devastated the city. In 1964 the magnitude 9.2 Great Alaska earthquake became the largest ever recorded in North America, while the 1994 Northridge quake near Los Angeles caused tens of billions of dollars in damage despite its moderate magnitude of 6.7.