Earthquakes Flashcards
What are seismic waves?
The vibrations from earthquakes that travel through the Earth
What are the human causes of seismicity?
Fracking, mining, and reservoir construction
What are the physical causes of seismicity?
Plate tectonics
What are the 4 types of waves that are a result of earthquakes?
Primary/pressure waves
Secondary/shear waves
Surface love
Rayleigh
Where do the 4 types of waves originate from?
The focus or the epicentre, they move in different directions
What are primary/pressure waves?
They are the fastest. They reach the surface first. They are high frequency. They travel through both the mantle and the core to the opposite side of the earth
What are secondary/shear waves?
These waves are half as fast and reach the surface next. They are high frequency but shake like a skipping rope. They can travel through the mantle but not the core
What are surface love waves?
These waves are the slowest and cause most of the damage. the move from side to side. Originates from the epicentre
What are Rayleigh waves?
These radiate from the epicentre in complicated low frequency rolling motions. They move up and down
What hazards are associated with seismicity?
Earthquakes, landslides, shockwaves, liquefaction, and tsunamis
What methods are used to measure the magnitude of an earthquake?
Richter scale
Mercalli scale
Moment magnitude scale
What are primary effects of an earthquake?
Building and bridges collapse
Power lines collapse
Road and railway damage
Liquefaction to saturated soil
What are secondary effects of an earthquake?
- Injuries may result in disability or death if not treated
- Power cuts which then effect emergency services
- More buildings collapse due to liquefaction
What are long-term effects of an earthquake?
- Trauma and grief
- Loss of farmland and food production
- Expense of reconstruction
What are some warning signs that may indicate an imminent seismic event?
- Microquakes before the main tremor
- Bulging of the ground
- Electrical and magnetic changes within local geology
- Increased argon gas content in the soil
What are the main things in a prediction, prevention and protection plan?
- Earthquake proof building design
- Evacuation plans
- Practice
- Stockpiling of water, food and medical supplies
What is protection?
Constructing buildings so that they are safe to live in and will not collapse
What is prediction?
Attempts to forecast an event, where and when it will happen, based on current knowledge
What is preparation?
Organising activities and drills so that people know what to do in the event of an earthquake
