Compressional waves- sound waves that travel at a speed of 5 miles a second. They shake buildings horizontally.

       Faults- breaks in the earth either above land or in the water; such as the San Andreas Fault.

       Focus- the place where the rupture begins

.       Richter Scale- a scale of numbers that mearsure the strength of an earthquake

        Rigid plates- big peices of land that are pointy, curved, etc.; they are under the cust, which is the top of the land

        Rupture- to break

        Seismic waves- shear waves, which shake buildings vertically