Seismology, seismograph, seismometer
Waves

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

relative speeds of p- and s-waves

Three questions answered by the 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