Tectonics (Chapter 2)

Question 1

How do tectonic processes result in earthquakes?

Answer 1

• Earthquakes - Shaking of earths ground due to sudden release of energy in lithosphere
• Occure along plate boundaries, contain systems of deep fracture (faults)
  1. Rock masses on either side of the fault are pushed by tectonic forces
  2. Friction causes them to get locked, and stress builds
  3. When stress exceeds strength og the fault, the rocks snap and move to a new position suddenly
  4. This sudden movement causes seismic waves to be released resulting in ground shaking
• Point in the earth crust where seismake waves are released is knows as Focus
  
  • Focus is origin of earthquake
• Point on earths surface directly above focus is epicentre
  
  • Shaking is generally felt most strong near the epicentre

Question 2

How are earthquakes measured?

Answer 2

• Using seismometers that detect ground vibrations and determines the magnitude of the earthquake. Greater seismic energy = greater magnitude

2 Ways
* Richter and moment magnitude

Question 3

What is the richter scale?

Answer 3

• Calculates earthquake magntiude using length of the height of the largest wave recorded on seismometers
• Based on max seismic energy reached, instead of total seismic energy released throughout the earthquake
• Scale is logarithmic, magnitude 6 releases 32 times more energy than magnitude 5
• Limitation:
  
  • Would rate an earthquake with a single drastic spike in wave ebergy as having a higher magnitude than a log earthquake with many large intense waves
  • Underestimates longer earthquakes with release more overall energy bu rating them as having lower magnitudes even though they are likely to do more damage

Question 4

What is the moment magnitude scale?

Answer 4

• Measures earthquakes based on total energy released
• Generally more accurate, especially in magnitude 8 and above earthquakes
• Also logarithmic, magnitude 6 releasses 32 times more energy than magnitude 5