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What are Earthquakes?

What are Earthquakes?. Pgs. 120 - 125. Where do Earthquakes Occur?. Seismology – the study of earthquakes Most occur near edges of tectonic plates. Plates can push toward each other, away from each other, or slide past each other.

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What are Earthquakes?

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  1. What are Earthquakes? Pgs. 120 - 125

  2. Where do Earthquakes Occur? Seismology – the study of earthquakes Most occur near edges of tectonic plates. Plates can push toward each other, away from each other, or slide past each other. Movements like these cause breaks in the Earth’s crust called faults. Faults are especially common along boundaries of tectonic plates. The most active area for earthquakes is around the edges of the Pacific Ocean.

  3. What Causes Earthquakes? Stress builds up in tectonic plates as they move. Rock layers will deform in response to this stress. Deformation – change in the shape of rock in response to stress.

  4. Deformation of Rock Rock can deform in either a plastic or elastic way. Plastic deformation like molding a piece of clay does not lead to earthquakes. Elastic deformation like stretching a rubber band will cause an earthquake. Rock will only stretch so far before it breaks and releases its energy. Elastic rebound – the sudden return of elastically deformed rocks to its original shape. During elastic rebound an earthquake occurs.

  5. Are All Earthquakes the Same? Earthquakes will differ in strength and in depth at which they begin. The type of tectonic plate motion will determine the motion that produces the earthquakes.

  6. Plate Motion and Earthquake Types Transform plate motion will be found at strike-slip fault and produce moderate and shallow earthquakes. Convergent plate motion will be found at a reverse fault and produce a strong and deep earthquakes. Divergent plate motion will be found at a normal fault and produce a weak and shallow earthquake.

  7. How Do Earthquakes Travel? The energy that travels during an elastic rebound is found as seismic waves. Seismic waves are waves of energy that travel through the Earth. The waves that travel through the Earth’s interior are called body waves. Body waves are either P or S waves. Waves that travel at the Earth’s surface is called a surface wave.

  8. P waves P waves are the fastest seismic waves. Since they arrive first, they are referred to as Primary waves. The P also stands for pressure. Pressure is applied to rock in the same direction the wave travels. The stress applied to rock as the wave travels is pressure. They can travel through all parts of the Earth as well.

  9. S waves When rock is deformed side to side S waves are created. S or shear waves are the second fastest seismic waves. Shearing occurs perpendicular to the direction in which the wave travels. S waves cannot travel through liquid. S waves arrive after P waves and are also referred to as secondary waves.

  10. Surface Waves Surface waves move the ground up and down in circle as the waves travel along the surface. Surface waves travel slower than body waves, but can be much more destructive. Earthquakes are most damaging when surface waves shake the ground.

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