Earthquake Hazards and Seismic Waves

Earthquake Hazards

• Earthquake - a shaking of the ground caused by the sudden movement of rocks
• Two types of Earthquakes:
  • Tectonic - caused by movement along faults in the Earth's crust
  • Volcanic - caused by rising magma or lava beneath active volcanoes
• Active Fault - a fault that has moved within the last 10,000 years
• Fault Types:
  • Strike-slip - rocks sliding horizontally past each other
  • Normal - two blocks of crust pulling apart
  • Reverse - one block of crust moving on top of another
• Seismic Waves - waves of energy produced by earthquakes or explosions
• Earthquake Measurement:
  • Magnitude - a measure of the energy released at the earthquake's focus (represented by numbers)
  • Intensity - a measure of the strength of shaking felt by people in a specific area (represented by Roman numerals)
• PHIVOLCS Earthquake Intensity Scale (PEIS) - used to determine the intensity of an earthquake

Seismic Waves

• Seismic waves are waves of energy caused by the sudden breaking of rock within the Earth or an explosion.
• Different types of seismic waves:
  • Surface waves
  • Body waves

Earthquake Related Hazards

• Ground Shaking - disruptive up-down and sideways ground movement
• Ground Rupture - ground displacement due to fault movement
• Earthquake-Induced Landslides - failures in slopes due to earthquakes
• Liquefaction - a process where sediments behave like a liquid due to strong shaking, groundwater saturation, and loose granular sediments

Liquefaction

• Three factors for liquefaction:
  • Loose, granular sediment
  • Saturation of the sediment by groundwater
  • Strong shaking
• Types of Liquefaction:
  • Flow Failures
  • Lateral Spreads
  • Ground Oscillation
  • Loss of Bearing Strength

Tsunami

• Tsunami - also called "harbor waves" or "tidal waves"; sea waves resulting from ocean floor disturbance by earthquakes
• Two types of Tsunamis:
  • Local Tsunamis
  • Far Field or Distant Tsunamis

Volcanic Hazards

• Volcanic Eruptions - begin deep within the Earth, where intense heat and pressure cause rock to melt, forming magma
• Volcanic Hazards:
  • Ash Fall
  • Lahars
  • Pyroclastic Flows & Surges

Volcanic Gas Emissions

• Volcanic gases are released by erupting and even dormant volcanoes. Examples:
  • Sulfur Dioxide
  • Carbon Dioxide
  • Hydrogen Sulfide

Volcanic Tsunamis

• Volcanic Tsunamis are triggered by explosive eruptions near or under water, or by landslides of volcanic materials into bodies of water.

Lava Flows

• Lava Flows - streams of molten rock that emerge from a volcano's vent
• Lava Domes - pile up around a volcano's vent because the lava is too thick to flow

Hydrometeorological Hazards

• Hydrometeorology - the study of atmospheric and terrestrial phases of the hydrological cycle with emphasis on the interrelationship between them
• Factors affecting climate:
  • Latitude
  • Altitude
  • Distance from the sea
  • Prevailing winds
  • Ocean currents
  • Topography
• Cloud Types:
  • Stratus
  • Stratocumulus
  • Cumulonimbus
  • Altocumulus
  • Nimbostratus
  • Altostratus
  • Cirrus
  • Cirrostratus
  • Cirrocumulus
• Potential Hydrometeorological Hazards
  • Tropical Cyclones
  • Thunderstorms
  • Floods
  • Flash Floods
  • Storm Surge

Explore the critical concepts of earthquake hazards, including the types and measurement of earthquakes as well as seismic waves. This quiz covers tectonic and volcanic earthquakes, fault types, and the PHIVOLCS Earthquake Intensity Scale. Test your knowledge on these fundamental geological phenomena!