Earthquakes pg 123

  Seismometer- an instrument that measures earthquakes  Earthquake- is a series of low frequency shock waves traveling through earth  Tectonic plate motion builds up stress at plate boundaries and within the plates themselves.  Stress- is a force exerted inside a material.  Shear- exits when forces are acting in opposite directions on different parts of the same object. Tectonic Forces

  Divergent boundaries- Plate sections that are moving part.  Convergent boundaries- plates moving towards each other.  Transform boundaries- where plates slide past each other.

  Strain- any change in shape of a solid under stress.  Ductility- the amount of strain a material can endure without breaking  Some Rocks have elasticity. These rocks store energy which can cause a more serious earthquake. Strain and fracture

  Joints- cracks in rocks  Faults- occurs when the sections of rock on opposite sides of the crack move relative to each other  Most major fault lines in the United States are in mountain Ranges.  Dip slip fault- parallel to its dip  Normal fault- block above fault surfaces drops.  Reverse fault- upper block rises above lower block Section 6b Faults and Joints

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  Most earthquakes we feel happen at depths less than 45 miles.  Secondary earthquakes are called aftershocks.  Aftershocks result from potential energy still being stored in the rocks. The fault slips again which causes the after shock.  Aftershocks can go one for days, weeks or even months after the initial earthquake. Faults and earthquakes

  Seismometer are instruments that detect seismic waves (earthquake waves).  Seismographs include a seismometer and a way to record the wave changes  During normal activity the seismograph will draw a straight line. During a earthquake the straight line turns into a zigzag. The height (amplitude) of the zigzag (wave) shows how strong the earthquake was.  The bigger the amplitude the stronger the earthquake 6c Earth waves and Seismology

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  Body waves- earthquake waves that pass right through the earth.  P waves- Fastest body waves. Have small amplitude and short wavelengths. They can travel through both solid and liquid rock  S waves- have larger amplitude. Stronger and slower than P waves. They can travel through solid rock.  Surface waves- travel through earths surface. Have to basic waves Rayleigh and Love waves.  Rayleigh and Love waves are more destructive waves because they affect human structures. ( house buildings, roads, etc.)  Epicenter – Center; spot on earths surface directly  Focus- the center of an earthquakes activity. This is deep underground Type of Seismic Waves

 Richter scale- how the strengths of earthquakes are reported. Magnitude- indicates the energy released by the earth movement. This scale does not work well on earthquakes that have a magnitude over 7. Effects of Earthquakes

  Intensity- is a measure of how much damage actually results from the earthquake.  Earthquakes can last from a few seconds to a few minutes.  Modified Mercalli Intensity scale- Measures the destructiveness of an earthquake. The scale is  1 is a earthquake that leaves no visible damage. A 12 is total destruction to the whole building. Earthquake Intensity

  Building collapse, fire, tsunamis, and landsides are all hazards of earthquakes.  Many cities are enforce earthquake proof buildings and strict building codes.  Many cities have sensors in their gas lines. These sensor will turn the gas off if there is a break in the line. Earthquake Hazards