Basic difference: magnitude versus intensity

Basic difference: magnitude versus intensity

The magnitude of an earthquake is a measure of its size. For instance, one can measure the size of an earthquake by the amount of strain energy released by the fault rupture. This means that the magnitude of an earthquake is a single value for a given earthquake; on the other hand, intensity is an indicator of the severity of shaking generated at a given location â€' clearly, the severity of shaking is much higher near the epicentre than further away. Thus, during the same earthquake of a certain magnitude, different locations experience different levels of intensity.

To elaborate these distinctions consider the analogy of a boiler. The temperature at a location near the boiler is higher than that further away from it (see Fig. 16.10). When the boiler releases 100 watts of energy, the temperature at a location depends on the energy of the boiler and its distance from the boiler. Hence the wattage of the boiler is like the magnitude of an earthquake and the temperature at a location is like the intensity of shaking at that location.