2 Normally, rocks are pressed together tightly Earthquakes: vibrations through earth’s crustOccur when rocks under stress slip or shift along a faultNormally, rocks are pressed together tightly= not movingOr “locked”
3 Elastic Rebound Theory Rocks along each side of a fault are moving slowly.If the rock is “locked”, then stress will increaseWhen the rock is stressed beyond its capacity, the rocks separate, or fracture, at the weakest point, and then they spring back to their original positionAs rocks move they create vibrations, called Seismic Waves
4 Aftershocks: series of tremors caused by other areas adjusting to stress of the initial earthquake
9 Where do earthquakes occur? Along or near the edges of lithospheric platesJournal:Why do think that earthquakes occur in these areas? Explain the cause of the earthquakes!
10 Fault ZonesGroups of interconnected faults along a plate boundary
11 6.2 Recording Earthquakes Seismograph: instrument that detects and records seismic waves
12 Types of WavesThe different types of energy waves shake the ground in different ways and also travel through the earth at different velocities.
13 Types of WavesP wave: The fastest wave, and therefore the first to arrive at a given location.compression wave, alternately compresses and expands material in the same direction it is traveling.S wave : is slower than the P wave and arrives nextshakes the ground up and down and back and forth perpendicular to the direction it is traveling.Surface waves: follow the P and S waves.
14 Locating an Earthquake Scientists analyze the difference between the arrival of P and S waves .