Epicenter-the point on the Earth's surface directly above the focus of an earthquake

Focus- the center of intensity

Transform Boundary- when two tectonic plates slide along each others

S Wave- the secondary wave

P Wave-first wave to arrive at the seismograph

After Shock-a smaller earthquake following the main shock of a large earthquake

Richtor Scale- which defines magnitude as the logarithm of the ratio of the amplitude of the seismic waves to an arbitrary, minor amplitude