Chapter 8, Section 1

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Chapter 8, Section 1 What are Earthquakes?

• Seismology The study of earthquakes.
• Most earthquakes occur near the edges of
  tectonic plates where giant pieces of the Earths
  crust are moving over plastic rock. Earthquakes
  occur at or near fault lines where the sliding
  action of these tectonic plates causes vibrations
  felt as earthquakes.
• Deformation stress caused by the bending,
  tilting or folding of rock layers causing them to
  change shape.
• Plastic Deformation rocks bend but do not
  break these do NOT cause earthquakes.
• Elastic Deformation rocks stretch and then
  break creating the vibrations of seismic waves
  that cause earthquakes and then return to their
  pre-deformed shape.
• Strike/Slip Faults are the cause of most
  earthquakes. These faults occur at transform
  plate boundaries.
• Earthquake Zones Areas where large numbers of
  faults are located parallel to tectonic plate
  boundaries.

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• Seismic Waves Energy waves that travel in all
  directions through the Earth.
• Types of Seismic waves
• 1. Body Waves seismic waves that
  travel through the interior of the Earth.
• a. Primary or P Waves These are
  the fastest moving seismic waves thus, the first
  to be detected. These waves travel with a back
  forth motion.
• b. Secondary or S (shear) Waves
  These are the second fastest, hence the second
  waves to be detected. S waves travel with a side
  to side motion.
• 2. Surface or L (long) waves These are
  the slowest of the waves and travel along the
  Earths surface.

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Chapter 8, Section 2 Earthquake Measurement

• Seismograph The instrument that records the
  time and intensity of the seismic waves and helps
  locate the epicenter of seismic events.
• Seismogram The tracing or paper record of the
  earthquake motion created by the seismograph.
• The most direct method of locating the epicenter
  of an earthquake is to measure the time
  difference between the arrival of the S waves and
  the P waves (S P Time Method) as recorded on
  the seismogram.
• Focus The origin or starting point deep within
  the Earth where the earthquake begins along the
  fault.
• Epicenter The point on the Earths surface
  located directly above the focus.

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Chapter 8, Section 2 Earthquake Measurement

• Richter Magnitude Scale Measures the strength
  of the earthquake by measuring the amount of
  ground motion.
• Magnitude A measure of the strength of the
  Earthquake. Each single number increase on the
  Richter Scale increases the strength of the
  earthquake by a factor of 10. For example, a
  magnitude 6 earthquake is 10 times greater than a
  5 and 100 times greater than a 4. The highest
  number on this scale is a 9.
• Intensity How much ground shaking is felt by
  people or how much damage a quake causes. This is
  measured on the Mercalli Intensity Scale. A
  single earthquake can have a variety of
  intensities levels with the highest near the
  epicenter decreasing outwards. The highest number
  on this scale is XI.

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Chapter 8, Section 3 Earthquakes Society

• Earthquake Hazard How likely an area is to have
  an earthquake based on past and present seismic
  activity. The west coast of the U.S. has the
  highest probability in our country.
• Earthquakes prediction is very difficult but
  scientists do observe patterns and are able to
  make generalized predictions.
• Gap Hypothesis A hypothesis that states sites
  along active faults with few earthquakes will
  have strong earthquakes in the future.
• Seismic Gaps Areas along a fault where a
  relatively few number of earthquakes have
  occurred.

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Chapter 8, Section 3 Earthquakes Society

• Retrofitting The process of making older
  buildings earthquake resistant by reinforcing
  their foundations with steel.
• Earthquake Resistant The addition of weights to
  dampen seismic vibrations, cross-bracing and
  shock absorbers to reduce the push-pull effect
  of earthquakes that causes building to sway.
• Before the Quake
• 1. Place heavier objects on lower shelves.
• 2. Develop a plan to get away from possible
  falling objects as well as a meeting place.
• 3. Stockpile food and water.
• During the quake
• 1. If indoors, get under a heavy table to
  protect yourself from falling objects.
• 2. If outside, stay away from anything that
  could fall on you, finding a clear area is best.
• 3. If in a car, stop and stay inside the car.