Chapter 5 Earthquakes

Chap 5, Sec 2 (Measuring Earthquakes) Objectives: How does the energy of an earthquake travel through Earth? What are the different kinds of seismic waves? What are the scales used to measure the strength of an earthquake?

Tech Terms: focus – the point beneath Earth’s surface where the earthquake occurs (rock under stress breaks). epicenter – the point that is on the surface, directly above the focus.

seismic waves – vibrations that travel through Earth, carrying the energy released during an earthquake. P waves – PRIMARY…these arrive first (movement is like an accordion).

S waves – SECONDARY…these arrive second (vibrate side to side and up and down). seismograph – an instrument used by geologists to measure the vibrations of seismic waves. magnitude – a number given to the relative size of an earthquake