Earthquakes Flashcards
What is an earthquake (EQ)?
the shaking of the Earth’s crust in the release of pressure
What 2 reasons might we get EQs in the UK?
old fault lines being reactivated
human activity such as fracking
What are seismic waves?
vibrations from earthquakes that travel through the Earth
What waves are first to arrive after an EQ?
P-waves
What are faster, S-waves or P-waves?
P-waves
What surface waves have an orbit that is similar to ocean waves?
Rayleigh Waves
What is meant by an EQs magnitude?
the quantitative measure of energy released at the source of an earthquake
What 2 ways measure the magnitude of an EQ?
the Richter Scale
the Moment Magnitude Scale (MMS)
What does the Mercalli scale measure?
the intensity of EQs
What are 2 primary hazards of EQs?
- ground shaking
- ground rupturing
Give 2 factors that can impact the severity of ground shaking in an EQ
- local geology
- depth
- magnitude
- distance from epicentre
What is soil liquefaction?
violently shaken soils with high water content lose their mechanical strength and start to behave like a fluid
What are 4 secondary impacts of EQs?
- tsunamis
- fires
- soil liquefaction
- landslides/avalanches
Briefly outline how tsunamis are formed
- destructive margin
- over-riding plate becomes distorted
- plate rebounds, displacing a large amount of water
What are features of a tsunami when out at sea?
- very fast (up to 700km/hr)
- very short in height (>1m)
- very long wavelength (up to 100km)
- calm conditions
