Seismic Hazards Flashcards
How is seismicity (strength of seismic waves) measured?
On the Richter scale
What scale is used ro show the rate of destruction caused?
Mercalli Scale
What are shockwaves (seismic waves)?
Energy released from the sudden jolt that vibrates through the ground
What is liquefaction?
When soil is saturated, the vibrations of an earthquake causes it to act like a liquid, soil becomes weaker and more likely to subside when it has large weight on it
What are the primary effects of a seismic hazard?
Environmental - fault lines which destroy the environment, liquefaction, Economic - businesses destroyed, Social - building collapse, killing/injuring people and trapping them, Political - government buildings destroyed
What are the secondary effects of a seismic hazard?
Environmental - radioactive materials and other dangerous substances leaked from power plants, saltwater from tsunamis flood freshwater ecosystems, soil salinisation, Economic - economic decline as businesses are destroyed (tax breaks etc), high cost of rebuilding and insurance payout, sources of income lost, Social - gas pipes rupture starting fires which can kill, water supplies are contaminated as pipes burst spreading disease and causing floods, tsunamis lead to damaging flooding, Political - political unrest from food shortages or water shortages, borrowing money for international aid, can be initial chaos and lawlessness eg. looting
What is done for prevention of a seismic hazard?
Cannot be prevented, liquefaction of soils can be prevented through soil stabilisation (gravel columns can be put in the ground), avalanches can be prevented through controlled explosions
What is done for preparedness of a seismic hazard?
Earthquake prone areas (eg. Japan) have extensive awareness strategies and education in place (eg. Drop, cover, hold on), earthquake warning systems and tsunami warning systems, evacuation plans and training (for emergency services)
What is done for mitigation of seismic hazards?
Search and rescue, immediate emergency aid, evacuation (short term), demolishing older, unsafe buildings, tsunami wave breaks and sea walls
What is done for adaptation in a seismic hazard?
Move away from area at risk, capitalise on opportunities such as encouraging tourism, insurance if living in place of risk, changing lifestyle (eg. Moving valuable items so they cannot fall), building specially designed earthquake prof buildings
How do seismic hazards occur?
Plates don’t move in fluid motions, at any boundary, plates become stuck due ro the friction between plates, pressure builds so much it cannot be sustained and the plates eventually gives way, pressure releases quickly causing a jolting motion in the plates, jolt is responsible for seismic movement spreading through the ground
What is the focus?
The place in the crust where the pressure/seismic energy is released
What are asiesmic buildings?
Buildings designed ro with stand or minimise destruction
What is the epicentre?
The point on the surface, directly above the earthquakes origin
What are Love Waves?
A surface earthquake wave with horizontal displacement
What are primary waves?
An earthquake wave causing compressions within the body of rock
What are Rayleigh Waves?
A surface earthquake wave causing both horizontal and vertical displacement
What are secondary waves?
An earthquake wave causing vertical displacement within the body of rock
