Seismic Hazards

Question 1

Focus

Answer 1

The breaking point

Question 2

Epicentre

Answer 2

The point on the surface directly above the focus

Question 3

Depth of focus and its effects

Answer 3

Shallow focus earthquakes (0-70km deep) tend to cause the greatest damage and account for
75% of all earthquake energy released.
Intermediate focus earthquakes occur between 70-300km
Deep focus earthquakes occur at depths of 300-700km.

Question 4

Body waves

Answer 4

Are shockwaves that travel through the earth
There are two types of body waves: primary and secondary

Question 5

Primary (P) waves

Answer 5

travel through both liquids and solids and are the fastest waves, reaching the surface first.

Question 6

Secondary (S) waves

Answer 6

also travel through the Earth, but unlike primary waves, they cannot travel through solids such as the core.

Question 7

Surface waves

Answer 7

travel along the Earth’s surface. Because they cannot travel through the mantle and core

Question 8

Love (L) waves

Answer 8

are the slowest waves but they are the most destructive.

Question 9

Rayleigh (R) waves

Answer 9

travel out from the epicentre near the surface.

Question 10

Tsunamis

Answer 10

These are giant sea waves generated by shallow-focus underwater earthquakes involving movements of the seabed

Question 11

Liquefaction

Answer 11

occurs in unconsolidated sediments that are saturated with water. Such sediments are made of loosely arranged particles that are not joined together and behave like a liquid when shaken by seismic waves.

Question 12

Landslides

Answer 12

is a rapid movement of earth materials down a slope, the materials ranging from huge boulders to soil.

Question 13

Magnitude of earthquakes

Answer 13

The Richter scale is a logarithmic scale. The scale starts at 0 and each number is ten times the magnitude of the one before it.