Seismology, seismograph, seismometer
Waves

longitudinal (compressive, primary, p-wave)
transverse (shear, secondary, s-wave)
surface

relative speeds of p- and s-waves
how far away is the earthquake
determination of the epicenter of an earthquake
how do we know that the core is molten
mohorovicic discontinuity
Richter scale (logarithmic)
what makes earthquakes dangerous
earthquake safety

Useful links:

Seismic areas on world map
Geothermal sites on world map