Earthquakes 2 / Tsunamis Flashcards
Explain Earthquake Hazards?
Any physical phenomenon that may produce adverse effects on human activities
Explain Primary vs Secondary Hazards
Primary: caused by fault movement (ground shaking)
Secondary: casued as a consequence of ground shaking (ground shakes, than things happen)
Explain the primary hazards at Christchurch?
- collapse of 2 buildings
185 deaths, 7000 injured
combined faults: surface rupture over a distance of 120 km
Explain secondary Hazards at Christchurch
- Land Elevation change
Explain Liquefaction (Secondary hazard)
what are the 3 ingrediants for liquefaction?
- Loose Sandy or silty soil
- Saturated Soil
- Ground shaking
What are the impacts of liquefaction on water quality and habitats
- Cloudy or contaminated water
- Decreased levels of O2
- Habitats smothered by silt (reduce biodiversity)
- Decrease in air quality
What is liquefaction
do to shaking of earthquake, soil loses its strength, and behaves like a solid
What is a Subduction Zone Earthquake
aka Megathrust earthquakes
- convergent plate boundaries
- subduction zones are only plate boundary that produces earthquakes over M8.5
What is a thrust fault?
Less than 45 degrees
What is “Asperity”?
Area on an active fault that is stuck or locked
- Subduction zone - wide
What are the 3 plates on the Cascadia Subduction zone?
Juan De Fuca, Explorer, Gorda
What is a Tsunami?
Wave or series of waves caused by a displacement of a large volume of water
how are tsunamis generated?
by seismic activity, landslides, volcanic eruptions
Explain wavelengths
- very long
- wave heights over 1m (in deep ocean)
- increase in height closer to land
Tsunami Causes
- Seismic activity
- Landslides
- Volcanic Eruptions
- Meteor impact
What earthquake magnitude on richter scale does it need to be for damaging tsunami to occur
M7.5 or greater
What 3 things happens when waves approach land?
- water depth decreases
- wave speed decreases
- wave height increases
Name some tsunami impacts
- destruction of land and infrastructure
- debris carried by water
- injury and death
- contaminated drinking water
- Disease (malaria and cholera)
- Impacts don’t dissapear overnight, can be many years till recovery
Explain the Sumatra - Andaman Earthquake (occurred in Indian Ocean)
- M9.1; MM =IX in areas
- Rupture along fault between Burma Plate and Indian Plate
- No warning system in Indian Ocean
What is the Tsunami warning system name?
DART: Deep-Ocean Assessment and Reporting Tsunamis
