The
three
basic
types
of
seismic
wave
generated
by
an
earthquake
at
its
focus
are
P‐
waves,
S‐waves,
and
Surface
waves.
P
and
S‐waves
are
body
waves
and
travel
through
the
interior
of
the
earth.
P‐waves
have
the
greatest
velocity
and
reach
the
seismic
station
first.
S‐waves
arrive
at
the
seismic
station
after
the
P‐waves.
The
amount
of
time
that
passes
between
the
P‐wave
arrival
and
the
S‐wave
arrival
is
important
in
helping
seismologists
determine
the
epicenter
of
the
earthquake.