The most powerful quake ever known to strike the United States occurred at New Madrid, Mo., in 1812.

After the 1811 and 1812 earthquakes in New Madrid, Missouri, it is one of the most powerful and damaging quakes to hit the southeastern United States.

A second, less powerful quake, measuring 4.0 on the Richter scale, struck in the early evening.

The most powerful quake on record in the region was in 1944.

On October 25, 1957, Pontremoli and Borgotaro were struck again by a very powerful quake.

The powerful 30-second offshore quake was felt in Guatemala, El Salvador, Belize, and as far as Cancún in Mexico.

These were in a good state of preservation prior to the rupture, suggesting it was one of the most powerful quakes in the region for approximately 900 years.

A subsidiary, Formosa Heavy Equipment, rebuilt 16 elementary schools after the 921 earthquake, the most powerful quake in Taiwan in decades.

Engineers have to go back to the drawing board to determine how best to reinforce structures, road and bridges to survive possibly more powerful quakes.

Volcanologists said Monday that the powerful quake destabilized a fragile dome at the mountain's peak.