earthquake basics

Question 1

how to measure

Answer 1

MMS (moment magnitude scale)
- accurate, better at measuring larger earthquakes
-measures total energy released in moment thru size of waves, amount of slippage, area of fault surface broken, and resistance of affected rock
-1-10 logarithmic scale (10x last number)

Intensity (effect on people, structures, natural env) measured by Modified Mercalli Intensity Scale

• takes obervations from people who experiences and rates on scale from 1 to XII

Question 2

hot spot and example

Answer 2

an area in the earths mantle where magma is unusually hot and rises to earths surface by convection - magma rises thru weaknesses in rock

• Hawaiian islands by mid pacific hotspot

Question 3

divergent
type of earthquakes and volcanic activity

Answer 3

plates move apart by convection currents
-causes new crust to form
- can cause mid ocean ridges (underwater mountains) in oceans or rift valleys on continents

-shallow focus earthquakes
-regular volcanic eruptions create submarine volcanoes which can grow above sea level (islands)

-ridge valleys stretch crust and break into faults - land in faults collapses, forming steep sided rift valleys

• Eyjafjallajokull Iceland 2010

Question 4

convergent - oceanic v continental

Answer 4

• plates move towards each other
• oceanic plate denser so it sinks, goes to mantle and melts from subduction
  -deep ocean trenches mark where plates meet
  -subduction causes fold mountains as continental plate folds

-friction created and subduction causes deep earthquakes in Benioff zone
-magma created by subduction pushes up through faults in continental crust and reach surface = eruption and composite volcanoes

-Philipines

Question 5

convergent - continental v continental

Answer 5

-collision margin occurs
-sediment between them is crumpled and forced up to create high fold mountains
-there can be subduction (e.g. nepal earthquake) when compressed (denser) sediment is subducted

-earthquakes have shallow focus
-Himilayas

Question 6

conservative

Answer 6

• slide past each other
  -cause major break in crust called a fault
• large scale fault = transform fault which affects wider area

-no crust made or destroyed so no volcanic activity
-powerful earthquakes, shallow focus

-san andreas fault, california
-haiti
-christchurch, NZ

Question 7

primary effects

Answer 7

-ground shaking

-crustal fracturing = earths crust cracks, leaving gaps

Question 8

secondary effects

Answer 8

-liquefaction = violent shaking makes surface rock lose strength and become more liquid and buildings(roads sink/tilt
more likely on soft mud, sand, and gravel
e.g. christchurch as city underlain with sand and silt

-landslides/avalanches = stress on slopes, high relief means more likely

• tsunami = underwater earthquakes