2Rocks move along faults. Fault: A fracture, or break, in the Earth’s lithosphere, where blocks of rock move past each other.
3The rocks bend as stress is put on them. Stress: the force exerted when an object presses on, pulls on, or pushes against another object.
4A sudden release of stress in the lithosphere causes an earthquake. Earthquake: The shaking of the ground caused by the sudden movement of large blocks of rock along a fault.
5The strength of an earthquake depends on: How much stress builds up before the rocks moveThe distance the rocks move along the fault
6Faults are classified by how rocks move. The three main types of faults are:Normal faultsReverse faultsStrike-slip faults
7Normal FaultsThe block of rock above the fault plane slides down relative to the other block.Stress that pulls rocks apart causes normal faults.Common in the Great Rift Valley of Africa.
8Reverse FaultsThe block of rock above the fault plane moves up relative to the other block.Stress that presses rocks together causes reverse faults.Common in the Himalaya Mountains.
9Strike-Slip FaultsBlocks of rock move sideways or horizontally on either side of the fault plane.Stresses that push blocks of rock horizontally cause earthquakes along strike-slip faults.The San Andreas Fault is a strike-slip fault.
10LiquefactionLiquefaction: shaking causes water saturated sediments to lose strength and act as if it were a liquid3 factors are required for liquefaction to occur:1. loose sand and silt grains2. water filling the space between the grains3. strong shaking
11Energy from earthquakes travels through Earth. The energy travels as seismic waves.Seismic waves: vibrations caused by earthquakes.
12All earthquakes start beneath Earth’s surface. Focus of an earthquake: the point underground where rocks first begin to moveEpicenter: the point on Earth’s surface directly above the focusIf two earthquakes of equal strength have the same epicenter, the one with the shallower focus causes more damage.
13Earthquakes produce three types of seismic waves: Primary wavesSecondary wavesSurface waves
14Primary Waves or P waves Fastest seismic wavesThese waves are the first to reach any particular location after an earthquake occurs.Can travel through solids, liquids, and gases.As these waves pass through a material, the particles of the material are slightly pushed together and pulled apart.
15Secondary Waves or S waves These are the second seismic waves to arrive at any particular location after an earthquake.Secondary waves travel through Earth’s interior at about half the speed of primary waves.Only travel through solids.As these waves pass through a material, the particles of the material are shaken up and down and side to side.
16Surface WavesSeismic waves that move along Earth‘s surface, not through its interior.These waves make the ground roll up and down in a rolling motion.Surface waves cause the largest ground movement and the most damage.Surface waves move the slowest.
17Seismic waves can be measured. Seismic stations are places where ground movements are measured.Seismometer: an instrument that constantly records ground movementSeismogram: the recording produced by a seismograph
18Earthquake magnitude scales describe the huge range in energy. Magnitude is the measure of an earthquake’s relative sizeRichter scale: this scale is based on how fast the ground moves at a seismic stationMoment magnitude scale: this scale is based on the total amounts of energy released by earthquakes