Hazards - Earthquakes Flashcards
What is an earthquake?
An intense shaking motion experienced in the surface of the crust due to stress suddenly being released
What is the focus of an earthquake?
The point where pressure is released in the crust
What is the epicentre of an earthquake?
The point on the surface that experiences maximum ground shaking
What percentage of all earthquake energy released are from shallow focus earthquakes?
75%
How deep are shallow focus earthquakes?
0-70km
How deep are intermediate focus earthquakes?
70-300km deep
How deep are deep focus earthquakes?
300-700 km deep
Name 3 cities where seismically active regions coincide with dense populations
Islamabad
Istanbul
Lima
What is the richter scale?
A logarithmic scale for measuring magnitude of earthquakes
WHat are seismic waves?
Shock waves moving through rock
What are the 4 types of seismic wave?
Primary
Secondary
Rayleigh
Love
Which seismic waves are body waves?
P and S
Which seismic waves are surface waves?
R and L
Descibre primary waves
Travel through solids and liquids
Fastest - 5.5km/s
Compressional
Describe secondary waves
Travel through solids
Slower - 3km/s
Longitudinal
What are the 2 different categories of seismic waves?
Surface
Body
Order a seismometer feels waves
PSLR
Which type of waves are the most destructive?
Surface waves
Describe the motion of Rayleigh waves
Rolling motion
How do love waves shake the ground?
Perpendicular to direction of movement
What is the Mercalli scale?
A measure of intensity of earthquakes by people giving subjective opinions on how strong the ground was shaking
What is a problem with the Richter scale?
It hasn’t been as effective on magnitudes of over 6 as energy is lost in the movement of the machine
What are the primary impacts of seismic events?
Ground shaking
Ground rupture
What are the secondary impacts of seismic events?
Soil liquefaction Landslides Tsunamis Fires Effects on people and built environment
