The Layered Structure of
the Earth
, Finding an Epicentre
• The focus is the origin of the earthquake where the energy is
released from, whilst the epicentre is the point directly above the
focus at the Earth’s surface.
• One earthquake will produce three vibrations on the seismogram, P, S
and L waves. Plotting the arrival times for these waves at many
seismometer stations at increasing distances from the epicentre gives
a distance-time curve from which the speed of the wave can be
calculated.
, Finding an Epicentre
• The time gap between the arrival of P and S waves increases with
distance from the epicentre. The time gap on the time-distance curve
gives you the distance of your seismometer from the epicentre. You
know how far away the epicentre is, but it could be in any direction.
Using the distance from at least three seismograms, you can
determine the location of the epicentre.
the Earth
, Finding an Epicentre
• The focus is the origin of the earthquake where the energy is
released from, whilst the epicentre is the point directly above the
focus at the Earth’s surface.
• One earthquake will produce three vibrations on the seismogram, P, S
and L waves. Plotting the arrival times for these waves at many
seismometer stations at increasing distances from the epicentre gives
a distance-time curve from which the speed of the wave can be
calculated.
, Finding an Epicentre
• The time gap between the arrival of P and S waves increases with
distance from the epicentre. The time gap on the time-distance curve
gives you the distance of your seismometer from the epicentre. You
know how far away the epicentre is, but it could be in any direction.
Using the distance from at least three seismograms, you can
determine the location of the epicentre.
