1. An earthquake is a shaking of the ground. Earthquakes occur when rock underground shifts or moves after stress increased (becasue of friciton). Stress will build up where there is a fault and then eventually this stress will cause an earthquake to occur. The rock will then break, at the focus, and trigger an earthquake. Earthquakes occur at faults, often near plate boundaries.
- P-waves, or primary waves move in a straight forward motion. They compress and expand the ground.
- S-waves, or secondary waves moves side to side or up and down and shake the ground back and forth.
- Surface waves travel at the earth's surface and they travel more slowly than S or P waves. The can make the ground roll or shake and can often cause a lot of damage.
3. P-waves arrive first, then S-waves, then surface waves. A seismograph would detect them in this order.
4. The Richter and Moment Magnitude scales rate the size of an earthquake (and the amount of energy released). The Mercalli Scale rates the amount of damage in a specific area.
One single earthquake will only have one Moment-magnitude and Richter rating. However an earthquake can have more than one Mercalli rating. This is because in different cities the damage done by and earthquake may be different, meaning more than one Mercalli rating.
Also, the Moment-magnitude scales is better than the Richter scale at estimating the size of further away or larger earthquakes.
5. Each time an earthquake's magnitude increases by one point (example from a 4 to a 5), 32 times more energy was released.