seismic - nature and distribution Flashcards
what is an earthquake/how is it caused?
it occurs as a result from a slow build up of stress, as the crust is mobile and begins to move, as this tress is released an intense shaking occurs that lasts for a couple of seconds
what is the focus?
the point in which pressure is released within the crust
what is the epicentre?
the point directly above on the Earth’s surface
what can the depth of focus determine?
the impacts of an earthquake?
how deep in a shallow focus
0-70km
how deep is an intermediate focus?
70-300km
how deep is a deep focus?
300-700km
how much energy is released at a shallow focus?
75%
where do the vast majority of earthquakes occur?
at plate boundaries
which boundary produces the worst earthquakes?
destructive
where do earthquakes occur on a constructive boundary?
at a fault
what is an example of a fault?
san andreas, california
why do some earthquakes occur away from boundaries?
the reactivation of faults
how can human activity produce earthquakes?
can put pressure on underlying rocks through deep mining and large reservoir building
