Study of earthquakes and how their shock
waves travel through the Earth. By examining
the global pattern of waves produced by an
earthquake, seismologists can deduce the
nature of the materials through which they
have passed. This leads to an understanding
of the Earth's internal structure. On a
smaller scale artificial earthquake waves,
generated by explosions or mechanical
vibrators, can be used to search for
subsurface features in, for example, oil or
mineral exploration.