Hazards - Seismic hazards Flashcards
(43 cards)
What is an earthquake?
the sudden shaking of the Earth’s surface, caused by thr movement of tectonic plates along fault lines
What is seismic movement?
shaking of the Earth’s surface (seismic waves)
What is the epicentre?
the area above the ground that is directly above the focus
What is the focus?
the point at which the rock moves underground where the earthquake originates from
Where do earthquakes occur?
Along ALL plate boundaries
What are the 4 types of plate boundaries?
constructive, conservative, destructive, collision
How frequent are earthquakes?
they occur everyday all over the world, but they are not always felt
What % of earthquakes does the “ring of fire” account for?
90%
What % of earthquakes does the “alpine-himalayan belt” account for?
5-6%
What is the regularity of earthquakes?
random, there is no pattern
Is magnitude of earthquakes random?
Yes
Can you predict earthquakes?
No, however microquakes can give some prediction
What are some primary hazards caused seismic activity?
- ground shaking
- crustal fracturing
- buildings collapse
What are some secondary hazards caused by seismic activity?
- liquefaction
- landslides
- tsunamis
- avalanches
- fires
- displacement of people and the built environment
- cost of rebuilding
- economic decline
- political unrest (crime)
What is liquefaction?
when saturated soil loses its strength and becomes fluid-like due to shaking, causing ground to collapse and buildings to sink. Like quicksand
4 ways to manage seismic hazards:
- prevention
- predpardeness
- mitigation
- adaptation
How to prevent seismic hazards?
- cannot be prevented
- liquefaction can be prevented by soil stabilisation
- avalanches can be prevented through controlled explosions
What is soil stabilisation?
gravel columns in the ground
How to be prepared for seismic hazards?
- awareness strategies & education
- warning systems
- evacuation plans & training
How has Japan taught people to be prepared?
“Drop, Cover, Hold On”
How can we mitigate seismic hazards?
- search & rescue teams
- demolishing older, unsafe buildings
- tsunami wave breaks and sea walls
How can we adapt to seismic hazards?
- move away from the area at risk
- tourism to boost the economy e.g. San Andreas Fault
- change lifestyle choices e.g. move valuable objects so they don’t fall
- earthquake proof buildings
Causes of seismicity?
HUMAN = fracking, mining, reservoir construction
PHYSICAL = plate tectonics (all 4 plates)
Characteristics of P waves:
- expansions and compressions
- fastest
- reach the surface first
- go through all solids/liquids/gases
- high frequency
- 1st wave to occur
- travels through mantle and core
