Quarter 2

• What causes an earthquake?

  An abrupt slip on a fault
• What is an earthquake?

  It is the shaking of the Earth's surface due to the sudden release of energy in the lithosphere
• When is energy released during an earthquake?

  When the fault overcomes the friction movement
• What are faults?

  Thin zones of crushed blocks of rocks
• How long can faults be?

  From centimeters to thousands of kilometers long
• What are the orientations of fault surfaces?

  They can be vertical or horizontal
• What are the three kinds of faults?

  Strike-slip, normal, and thrust (reverse) faults
• What is the amount of ground displacement in an earthquake called?

  The slip
• How do strike-slip faults operate?

  Rocks slide past one another on a horizontal plane with little to no vertical movement
• What happens in normal faults?

  Two blocks of crust pull apart, creating a space
• How does the hanging wall move in a normal fault?

  The hanging wall moves downward with respect to the footwall
• What are reverse faults also known as?

  Thrust faults
• Where are reverse faults typically found?

  In collision zones where tectonic plates push up mountain ranges
• What is a fault in the context of tectonic plates?

  A weak point in the tectonic plate where pressure is released
• What is the focal point of an earthquake?

  The area inside the Earth where the earthquake starts
• What is the epicenter of an earthquake?

  The point at the Earth's surface directly above the focus
• Where does the strongest shaking occur during an earthquake?

  At the epicenter
• How do seismic waves from a deep-focus earthquake behave as they travel?

  They lose more energy as they travel farther to the surface
• What does magnitude measure in an earthquake?

  The energy being released from the origin of the earthquake
• What instrument measures the magnitude of an earthquake?

  A seismograph
• What does the Richter Magnitude Scale measure?

  The quantity of seismic energy released by an earthquake
• What is intensity in the context of earthquakes?

  The strength of the trembling made by the earthquake at a place
• How does the intensity of an earthquake vary?

  It varies depending on where you are
• What scale determines the intensity of an earthquake?

  The Mercalli Scale
• What are active faults?

  Areas along which displacement is expected to occur
• Why do all shallow earthquakes occur on active faults?

  Because a shallow earthquake produces displacement across a fault