These earthquakes can occur before or during eruptions, or as molten rock travels underground. Earthquakes are generally measured in terms of magnitude and intensity. The Richter Scale measures magnitude.
Ratings decrease with increasing distance away from an earthquake's source.
Local topography also affects earthquake hazards. Steep slopes composed of loose material may produce large landslides during an earthquake. The type of construction also affects the risks of damages to a property. For these reasons, earthquake hazards are highly localized and difficult to assign regional earthquake boundaries that share the same relative degree of hazard.