2 Review: Forces in the Earth’s Crust Shearing is the movement that happens to the crust along a Transform BoundaryTension is the movement that happens to the crust along a Divergent BoundaryCompression is the movement that happens to the crust along a Convergent Boundary
3 What are the 3 types of faults we have studied? Normal Fault:occurs when plates divergeresults from tensionThe hanging wall slips below the footwallReverse Fault:Occurs when plates convergeResults from compressionThe hanging wall moves up above the footwallStrike-slip Fault:Occurs when plates slip past each otherResults from shearingSideways motion, not up and down
4 Where do Earthquakes come from? PLATE TECTONICS!When plates move and create faults, the force exerted on the crust (compression, tension, or shearing) creates Earthquakes
5 What is the definition of an Earthquake? The shaking and trembling that results from tectonic plates shifting, causing rocks to break along fault lines and releasing energy throughout the earth’s interior.
6 What are the components of an Earthquake? Focus: the area within the Earth’s lithosphere where the rock breaks, triggering the EarthquakeEpicenter: the point on the Earth’s surface directly above the focus
7 Earthquake components: Seismic Waves Seismic Waves: the vibrations traveling through the Earth that carry the energy released during an Earthquake3 types of Seismic Waves:P waves (primary)S waves (secondary)Surface waves
8 Seismic WavesP waves: seismic waves that compress and expand like an accordionS waves: seismic waves that vibrate from side to side as well as up and downSurface waves: when p and s waves reach the epicenter, and move across the surface of the Earth in the motion of waves like the ocean
9 P-wave motion: S-wave motion: Waves in the Earth’s Interior: Slinky Demonstration:P-wave motion:They move the fastest and can move through solids and liquidsCan damage buildings when they reach the surfaceS-wave motion:Move more slowly than P wavesCannot move through liquids
10 Common Questions after Earthquakes: “How big was the quake?”“Where was the earthquake centered?”
12 Measuring Earthquakes Mercalli Scale: 12 step rating based on how much damage the earthquake causes on the surface of the EarthThe same earthquake can have different ratings at different locations--uses Roman numerals: I, II, III, IV, V, VI, VII, VIII, IX, X, XI, XII
13 Mercalli Scale:I-III: People notice vibrations like those from a passing truckIV-VI: Slight damage. People run outdoors.VII-IX: Moderate to heavy damage. Buildings jolted off foundations or destroyedX-XII: Great destruction. Cracks appear in the ground. Waves seen on the surface.
14 Measuring Earthquakes The Richter Scale: a measurement of an earthquake’s magnitude (the size of the waves)Scientists assign a magnitude by measuring an earthquake’s seismic wavesScientists use a SEISMOGRAPH to measure the seismic waves on a Richter ScaleProvides accurate measurements for small, nearby earthquakes. But does not work well for large or distant earthquakes
15 Measuring Earthquakes Moment Magnitude Scale:Estimates the total energy released by an EarthquakeMeasure the magnitude of the seismic waves, the strength of the rocks that broke, the distance that the fault slipped
20 Magnitude: tells how much energy was released by the earthquake Each one point increase in magnitude represents a release of 32 times as much energyEarthquake with a magnitude of 5 releases 32 times as much energy as an earthquake with a magnitude of 4