Changes

Earthquakes are a significant natural hazard to populations living in areas prone to them, and emergency responses to the hazard vary with economic development. The most powerful and destructive earthquakes occur at tectonic plate boundaries like the San Andreas Fault.

Earthquakes are a significant natural hazard to populations living in areas prone to them, and emergency responses to the hazard vary with economic development. The most powerful and destructive earthquakes occur at tectonic plate boundaries like the San Andreas Fault.

The severity of earthquakes is measured using the [[Moment Magnitude scale]], which replaced the [[Richter scale]] in the 1970s. The largest quake ever recorded had a magnitude of 9.5; it struck Chile in 1960.<ref>http://earthquake.usgs.gov/earthquakes/world/10_largest_world.php</ref> Technically the Moment Magnitude scale only measures the absolute magnitiude; the [[Mercalli scale]] is used to measure the felt magnitude - essentially how much the ground shakes over the epicentre of the quake.

The severity of earthquakes is measured using the Moment Magnitude scale, which replaced the [[Richter scale]] in the 1970s. The largest quake ever recorded had a magnitude of 9.5; it struck Chile in 1960.<ref>http://earthquake.usgs.gov/earthquakes/world/10_largest_world.php</ref> Technically the Moment Magnitude scale only measures the absolute magnitiude; the [[Mercalli scale]] is used to measure the felt magnitude - essentially how much the ground shakes over the epicentre of the quake.

==Causes of Earthquakes==

==Causes of Earthquakes==