Earthquakes.notebook
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January 03, 2020
Feb 21:20 PM
8.1 What is an Earthquake? Key Questions
What is a fault?What is the cause of earthquakes?
Fact:Thousands of earthquakes happen everyday. Earthquakes can happen near or away from plate boundaries. The people on the Earth’s surface can only feel a few earthquakes. Roughly 75 100 strong earthquakes occur per year.
Seismologystudy of earthquakes
Seismologistsa person that studies earthquakes and seismic waves
Earthquakes vibration of Earth produced by the rapid release of energy in the
lithospherecaused by fault movementstress on rocks causes plates to push, pull or slide pass each other80% occur along Pacific Plateoccur mostly in Earthquake Zones
Faultfractures in the Earth's crust where movement occursfault scarp vertical movementoffset/displaced horizontal movementfault creep slow gradual movement
Seismic waveswaves of energy that travels through the earthoccur mostly at edges of tectonic plates
Epicenterpoint on the Earth’s surface directly above the earthquakes starting
point
Focuspoint inside the earth where the earthquake begins
What causes an Earthquake?rapid release of energy due to the forces applied to the rocks
Deformationchange in shape of rocks due to stress which causes movement
Elastic energyenergy associated or stored stretching a rubber band
Elastic Reboundsudden return of elastically deformed rock to its undeformed
shape releasing the rubber band
Aftershockweaker earthquake that occurs after a major earthquake
Foreshocksmall earthquakes that occur before a major earthquake
1. Figure out how long the distance to the epicenter (in centimeters) is on your map.
2. Using your compass, draw a circle with a radius
equal to the number you came up with in step 1.
The center of the circle will be the location of your
seismograph. The epicenter of the earthquake is
somewhere on the edge of that circle.
3. Do the same thing for the distance to the epicenter
that the other seismograms recorded. Where they
cross is the location of the epicenter.
http://video.nationalgeographic.com/video/101videos/earthquake101?source=relatedvideo 3 min
Feb 51:14 PM
8.2 Measuring EarthquakesKey Questions
What are the two categories of seismic waves?How are seismic waves recorded?How is the size of an earthquake measured?How is an earthquake epicenter located?
Two Types of Seismic Waves Body Waves and Surface WavesBody waves
seismic waves that travel through the earth’s interior
Two types of body wavesP waves = primary waves, pressure waves,
compressional wave rocks move back and forth compress and release travel the fastest solid, liquid, gas
S waves = secondary waves, transverse waves, shear waves move like a snake = right angles to each other second fastest solid
Surface waves or Lateral (L) wavesmove in a circular motion or side to sidemost destructive
Comparison on next page Venn Diagram
How do we record Seismic Waves?Seismograph
records seismic wavesSeismogram
tracing of the motion of the earthquake by the seismograph
Measuring Earthquakes
Richter Magnitude Scaledeveloped by Charles Richter in 1930smeasured strength of earthquakes
magnitudemeasured strength of earthquakes, how much energy
was released
Look at Table 1 on page 225.Compare the magnitudes and number of earthquakes.
Modified Mercalli Scaleintensity
measure of the earthquake's effect
Look at Figure 7 on page 226.
Review Label A, B, C write characteristics about each
Locating an Earthquake page 227
1. Figure out how long the distance to the epicenter (in centimeters) is on your map.
2. Using your compass, draw a circle with a radius equal to the number you came up with in step 1. The center of the circle will be the location of your seismograph. The epicenter of the earthquake is somewhere on the edge of that circle.
3. Do the same thing for the distance to the epicenter that the other seismograms recorded. Where they cross is the location of the epicenter.
Jan 21:03 PM Jan 212:52 PM
8.4 Earth's layered StructureKey Questions
What are Earth's layers based on chemical composition?What are Earth's layers based on physical properties?How did scientists determine Earth's structure and
composition?
The Earth is divided into 3 Main Layers1. Crust
outermost layer oxygen, aluminum, calcium 1% of the Earth’s mass thickness varies: 5100 kmtwo types:
oceanic densercontinental
Mohorovicic Discontinuity Mohoseparates the crust and the upper mantle.
2. Mantlelargest layer 67% of Earth’s massmade of silicon, oxygen, magnesium, ironsolid and liquid: plasticlikeLithosphere
made up of the crust and upper mantledivided into tectonic plates
Asthenosphereplasticlike layer below the lithosphere plates float soft solid rock that moves very slowly
Mesospherethe lower part of the mantle to the outer core
Gutenberg Discontinuityseparates the mantle and the core
3. Core
innermost part of the Earth33% of the Earth’s mass
Outer coreliquidmade of iron and nickel
Lehmann Discontinuityseparates the outer and inner core
Inner Coresolid: due to the pressurevery dense iron and nickelscientists believe that the inner core rotates faster than therest of the planetspeed = lap the Earth's surface once every 400 years
A. Mohorovicic Discontinuity 1. Continental Crust 2. Oceanic Crust B. Gutenberg Discontinuity 3. Asthenosphere 4. Mesosphere C. Lehmann Discontinuity 5. Outer Core 6. Inner Core
Jan 21:02 PM
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