Earthquake Notes PDF

Faults  Faults A fault is any fracture or system of fractures along which Earth moves. Normal Reverse Strike-Slip 1 Fault 2 Fault 3 Fault  Normal Fault Movement along a normal fault is partly horizontal and partly...

Faults  Faults A fault is any fracture or system of fractures along which Earth moves. Normal Reverse Strike-Slip 1 Fault 2 Fault 3 Fault  Normal Fault Movement along a normal fault is partly horizontal and partly vertical. The horizontal movement pulls rock apart and stretches the crust. Vertical movement occurs as the stretching causes rock on one side of the fault to move down relative to the other side.  Reverse Fault Reverse faults form as a result of horizontal and vertical compression that squeezes rock and creates a shortening of the crust. This causes rock on one side of a reverse fault to be pushed upward relative to the other side.  Strike-Slip Fault Strike-slip faults are caused by horizontal shear. The movement at a strike-slip fault is mainly horizontal and in opposite directions Earthquakes Earthquakes Waves Seismic waves are the vibrations of the ground produced during an earthquake. Caused when irregular surfaces in rocks can snag and lock along faults when movement occurs. The focus of an earthquake is the point of initial fault rupture, which is usually below Earth’s surface. The first body waves generated by an earthquake spread out from the focus  Earthquake Waves 1 Epicenter The point on Earth’s Primary Waves surface directly above (P waves) the focus squeeze and push rocks in the direction along which the waves are traveling. 2 Secondary 3 Waves (S waves) Surface Waves These waves are slower than P-waves. the third and slowest waves which travel only S-waves have a motion that causes rocks to along Earth’s surface. Surface waves can move perpendicular to the direction of the cause the ground to move sideways AND up waves. and down like ocean waves. Earthquake Waves A seismogram the record produced by a seismometer that can provide individual tracking of each type of seismic wave.  Earthquake Magnitude and Intensity The Richter scale, devised by a geologist named Charles Richter, is a numerical rating system that measures the magnitude of an earthquake. Magnitude is the measure of the energy released during an earthquake. Amplitude are the numbers in the Richter scale are determined by the height of the largest seismic wave. The moment magnitude scale is a rating scale of the energy released by an earthquake, taking into account the size of the fault rupture, the amount of movement along the fault, and the rocks’ stiffness.  Earthquake Hazards Structures 01 Pancaking is when the shaking causes a building’s supporting walls to collapse and the upper floors to fall one on top of the other like a stack of pancakes. Land and Soil 02 In sloping areas, earthquakes can trigger massive landslides. In areas with sand that is nearly saturated with water, seismic vibrations can cause the ground to behave like a liquid called soil liquefaction. Water 03 Tsunami is a large ocean wave generated by vertical motions of the seafloor during an earthquake. The closer the fault is to the shore, the higher the breaker and the more destructive!