How can earthquake waves help locate the source of a quake?

When an earthquake occurs, a wave of energy travels through the earth and it kind of resonates throughout the entire planet until the energy dissipates. By picking up the waves of energy at different locations, scientists can then compare the time the wave arrived and what its energy level was to triangulate the exact origin of the earthquake that caused it. And, different earthquakes can easily be differentiated from each other by the pattern of the markings on the seismograph. Each earthquake has its own signature pattern, kind of like a fingerprint.