Earthquakes

Earthquakes

1. Faults

   • Fractures on which sliding has occured
     • When one body of rock moves against another, a polished, slick surface forms called slickenside
       • Slickenside causes a surface with lines and grooves called a lineated surface
         • Fault slip lineations are linear marks on a fault surface created during movement on the fault
   • Can cause earthquakes
   • Can appear above or below ground
   • Normal
     • When the hanging wall moves down relative to the hanging wall
   • Reverse
     • When the hanging wall moves up relative to the footwall
       • When one piece of the Earth moves up or down relative to another, it exposes a surface between the top of one piece and the middle of the other. It looks like a stair.
     • The hanging wall is the block above the fault line. The footwall is the block below the fault line
   • Strike-slip
     • When a piece of the Earth's crust slides sideways relative to another piece
       • If you are facing a piece of land during a strike-slip fault and it slides to your left, it's called left lateral. If it moves to your right, it's called right lateral.
   • Gouge is a powder that forms when faulting crushes the rock adjacent to the fault
   • Breccia are chunks formed when faulting crushes rock adjacent to the fault

2. Episodes of grand ground shaking

   • Caused by the breaking of rock (faulting) or a pre-existing fault

3. Do not occur instantaneously after the rock breaks

4. Vibrations are what we feel during an earthquake

   • Vibrations: The transmission of energy from a place where something breaks
     • Provide a means to transmit energy from one location to another
       • Continuous shaking (of the Earth)

5. Focus (hypocenter) of an earthquake

   • The point within the Earth of which the slip causing an earthquake happens
     • Where the rock breaks and the energy is generated
       • When the energy is generated, it will propagate outwards in a series of waves

6. Epicenter

   • The point of Earth's surface directly above the focus of an earthquake
     • This is where we feel the quake

7. Stresses can lengthen or shorten rock

   • Tension is a force that stretches the rock and lengthens it
   • Compression is a force that squeezes the rock and shortens its length

8. Earthquake energy passes through rock in the form of waves

   • Body waves travel within solid rock of the planet
     • Compressional body waves (P-waves) are waves in which the atoms move back and forth, parallel to the direction in which the overall wave is moving
     • Shear body waves (S-waves) are waves in which the atoms move up and down, perpendicular to the direction in which the overall wave is moving
   • Surface waves travel along the surface of the Earth
     • Love waves are waves that move in a snake-like motion (side to side)
     • Rayleigh waves are waves that move in an undulatory motion (up and down)

9. Asperities are little protrusions or bumps in a surface that keep objects from sliding right off of the surface

   • Only when enough force is exerted on the object will the asperities break off and allow it to move

10. To erode is to be carried away by water or other geologic phenomenons