Hazardous earth

- Primary wave

- Fastest (first to be detected on seisometer)

- Can move through solid rock and liquid (therefore fastest as takes the shortest journey)

- particles move in the same direction as the wave and it's energy

(Slinky movement)

- Secondary waves

- Slower than primary

- Can only move through solid rock and NOT liquid (this led to the belief that the outer core is liquid)

- particles move side to side and up and down, perpendicular to the direction of the wave

- Only travel through the crust

- lower frequency (occur less) than body waves

- Easily distinguished on a Seismograph

- Almost entirely responsible for damage and destruction in earthquakes

- Deeper the focus= damage and strength of wave decreases

- Two types: love wave and Rayleigh Wave

- Fastest

- Moves ground from side to side

- Creates the longest strokes on Seismograph

- Only in crust- so come last, after body waves

(Bike)

- Rolls along the ground

- Moves ground up and down

- Cause most of the shaking felt

- Compressional= rocks pushed together

- Tensional stress= rocks pulled apart

- Shear stress= rocks slide past in opposite directions

Foreshock= mild tremour before the violent shaking of the earth

Aftershock= Smaller earthquake after a larger one

Focus= location below ground where earthquake started

Epicentre= point at the earth's surface directly above the focus

Detects and record seismic waves, these are set up at various location around the globe

Seismic wave= vibrations that carry energy from source of earthquake outward (through interior of the earth)

- Uses the amplitude of sesimic waves to determine earthquake magnitude

- Created 1935

- Logarithmic (1 number up, increases by 10 fold)

- No upper limit (highest been 9)

- Doesn't express damage

- Measures earthquake intensity and its impact

- Relates gorund movements to impacts felt and seen by people at the location

- Qualitative- based on observation/ description

- More accurate than Richter- used by scientists

- Most accurate for larger earthquakes (4.5+) as uses amount of physical movement

- Not used for smaller earthquakes as these are hardly felt by people

- Vertical and horizontal movement of the ground

- Severity depends on:

Earthquake magnitude

Distance from epicentre

Local geology

- Extreme shaking= close to epicentre, high magnitude, unconsolidate surface, high water content. E.G Mexico City 1985

- Buildings withstand verticle movements better than horizontal movements

- displice rocks on fault lines

- Rip apart sewers, pipes, railways, roads

- Disrupt natural drainage eg. rivers/ aquifers- can impact public water/ irrigation

Earthquake in area of ine grained sands, alluviu, landfill and water, the vibrations can cause these to act like a liquid

- As the material loses strength slopes collapse, structures tilt and sink

E.G. Kobe earthquake- 200 boats destroyed affecting Japanese economy

- Ground shaking and liquiefaction cause slope failure

- Steep slopes in mountains especially vulnerable (increased by deforestation and heavy monsoon rains)

- Nepalese earthquake 2015, triggered a large number of landslides and avalanches (avalanches are another hazard, quick downfall of snow)

- Landslides block roads in mountains, and block rivers creating lakes which threatens downstream with floods if dams fail, EG. Kashmir 2005

- Reservoirs in upland, movement could displace water and break sides eg. Italy 1963

- Sea bed rises vertically, displacing water above producing powerful waves

- Out at sea they have a short wave height and long wave length

- Height increases near shore at shallow water

- Before wave breaks, water in front of water is pulled back out to sea= drawdown

- Rushes to land as wall of water over 25 metres

- Height affected by topography of sea bed

- Depends on relief on how far tsunami reaches inland

- Underwater landslides (rock slopes down hill) caused by earthquakes water can be displaced= tsunamis