Chapter 4 Earthquake - vibrations caused by sudden release of large amounts of energy on movement of a fault. Fault - a break in earth's crust where movement occurs. Numbers become smaller away from earthquake. Measures maximum amplitude of ground shaking.
All stations report same number.
Measure of total energy across entire displacement. Preferred by seismologists. Travel fastest - compressional waves. Vibrate parallel to the direction of travel. Travel through solids, liquids and gasses.