EARTHQUAKE HAZARDS

• ● refers to a force called shock

  ● shaking of the ground caused by sudden motions along

  fractures in the Earth’s crust

  ● generates weak to strong shaking on the Earth’s surface

  ○ movement of rock materials underneath

  Earthquakes
• Causes of earthquakes:

  • movement of tectonic plates
  • volcanic activity
  • man-made disturbances
• Which part of an earthquake is:

  ★ fracture in the rocks that make up the Earth’s crust

  ★ where earthquakes occur

  ★ planar features

  Fault
• Which part of an earthquake is:

  ★ point at the surface of the Earth directly above the focus

  ★ where the shaking is most intense

  Epicenter
• Which part of an earthquake is:

  ★ point within the Earth where an earthquake rupture

  starts

  ★ marks the origin of the earthquake

  Focus (Hypocenter)
• Which part of an earthquake is:

  ★ constantly moving

  ★ massive rocks that make up the outer layer of the

  Earth’s surface

  ★ movement along faults triggers earthquakes

  ★ earthquakes occur when plates interact with each other

  Plates
• Which part of an earthquake is:

  ★ waves that transmit energy released by the earthquake

  ★ causes the shaking of ground

  ★ energy released from the focus

  Seismic Waves
• ➢ smaller earthquakes that occur within the vicinity of the

  main shock

  ★ follows the initial rupture

  ➢ caused by the re-adjustment of stress along the fault

  system

  Aftershocks
• Type of fault:

  ★ faults that result from horizontal tension stresses in

  brittle rocks

  ‣ pull rocks apart

  ★ hanging-wall block moves down relative to the footwall

  block

  ★ divergent plate boundaries

  ‣ plates are moving away from each other

  Normal Fault
• Type of fault:

  ★ faults that result from horizontal compressional stresses

  in brittle rocks

  ★ hanging-wall block moves up relative to the footwall

  block

  ★ convergent plate boundaries

  ‣ plates are colliding

  Reverse Fault
• Type of fault:

  ★ special case of reverse fault

  ‣ dip of the fault is less than 45°

  ★ hanging wall block move up and over the footwall block

  ★ can have considerable displacement

  ★ results in older rock layers overlying lower rock layers

  ★ compressional tectonic settings

  ‣ collision mountain belts

  Thrust Fault
• Type of fault:

  ★ faults that do not break the surface

  ‣ no visible surface rupture

  ★ rocks above the fault behaved in ductile function

  ★ rocks fold over the tip of the fault

  ★ can be only detected through geophysical techniques

  ★ poses seismic hazards due to stress

  Blind Faults
• Type of fault:

  ★ faults where the motion has taken place along a

  horizontal direction

  ★ pushing rock blocks past each other

  ★ parallel to the strike of the faults

  ‣ along the dip direction of the faults

  ★ minimal vertical displacement

  ★ transform plate boundaries

  ‣ plates slide horizontally past each other

  ★ Varieties:

  1. Left-Lateral Strike Slip Fault

  ○ block on the other side moves to the left

  b. Right-Lateral Strike Slip Fault

  ○ block on the other side moves to the right

  Strike Slip Faults
• Effects of an earthquake:

  • one of the most notable effects of the energy from the hypocenter
  • mostly affects the concrete structure from the surface
  • energy is transmitted in the from of seismic waves

  Ground Shaking
• 3 Classifications of Seismic Waves

  P-waves, S-waves, Surface waves
• Effects of an earthquake:

  • tension cracks
  • a phenomenon where ground movement occurs and the surface of the ground breaks
  • commonly present in areas located near or along fault lines

  Ground rupture or fissures
• Effects of an earthquake:

  • The sediment composition becomes "liquefied" in the sense that it assumes the dynamics of water flowing

  Liquefaction
• Effects of an earthquake:

  ★ land subsidence or sinking of the ground

  ★ major factor in an area’s susceptibility to flooding

  ‣ low-lying coastal areas and river deltas

  ★ precursor for the development of sinkholes

  ‣ can unexpectedly collapse

  Earthquake-Induced Ground Subsidence
• Effects of an earthquake:

  • Came from the Japanese term "tsu" - harbor, and "nami" - waves
  • a wave or series of waves in a wave train generated by the sudden, vertical displacement of a column of water

  Tsunami
• Effects of an earthquake:

  • landslides are mass movement of rock, soil, and debris down a slope due to gravity

  Earthquake-Induced Landslide