Earthquakes

Question 1

What is the moment magnitude

Answer 1

Measures size of earthquakes based on total energy released by an earthquake

Question 2

Advantages of using a moment magnitude

Answer 2

Accurate for all earthquake sizes from small/not felt earthquakes ( I on the modified mercali scale)
To very latge ones (VIII and above)
Unlike the Richter scale, which tends to underestimate the size of larger earthquakes making it consistent across all distances regardless of the distance from the earthquakes epicenter.

Question 3

Disadvantages of moment magnitude

Answer 3

Complex calculations as it requires detailed info about the fault which needs sophisticated equipment and time compared to simpler scales ( richter) which is aster , albeit (even though) less accurate

Question 4

What is the Richter scale

Answer 4

Based on amplitude of seismic waves

Question 5

Advantages of Richter scale

Answer 5

Quick real time measurements - determined almost immediately after an event = useful for rapid assessments of earthquake severity, especially in emergency response situations

Question 6

Disadvantages of richter scale

Answer 6

Limited to local earthquakes within 600km of the seismograph , making it less effective for distance earthquakes as at larger distance, seismic waves weaken and the scale becomes less accurate.

Question 7

Primary hazards of earthquakes

Answer 7

Ground shaking- shaking can cause the ground to crack/rupture=damage roads e.g. 2011 Tohoku earthquake led to significant damage from skating led to tsunami
Cristal fracturing- landforms change alter it, creating new faults and changes in elevation e.g. 1906 san Francisco eq caused surface rupture along st Andrea’s fault

Question 8

Secondary hazards

Answer 8

Liquefaction =dangerous phenomenon that caused catastrophic consequences
Saturated soil loses its strength and behaves like liquid due to ground shaking
damage roads=socio economic = harder for emergency services and prevents people going to work

Question 9

Tsunami formation

Answer 9

Subduction occurs undersea in Benioff zone
Displaces water column
Displaced waves form tsunami that spreads out in all directions with height 3m
As it reaches shore,vacuum effect occurs, exposing seafloor
Suction of water increases volume of water
Waves come crashing onshore in series of tsunami waves

Question 10

Physical factors affecting tsunami

Answer 10

A factor that affects severity is magnitude of eq undersea resulting from subduction of plates in Benioff zone. Increased mag=more energy released