prize9-4, Exercise 2: Magnitude 6 versus magnitude 7

Model answer (check the details):

Magnitude measures the energy released by the quake itself. A magnitude 7 releases about 32 times the energy of a magnitude 6. But deaths depend on intensity, the shaking at populated places, which depends on distance from the source, depth, ground type and the quality of buildings.

A magnitude 6 that is shallow and close to a city with weak, unreinforced buildings and soft ground can cause severe shaking and collapse. A magnitude 7 offshore, deep or in a region with strong building codes and well-prepared people can cause little loss of life.

Care: the point is that the hazard comes from the combination of the event and the exposure of people and buildings.