Earthquakes Flashcards
Define Faultline
A Faultline is the fracture in the rock caused when plates move
What is a focus?
A focus is the point on the Faultline where the earthquake begins
What are seismic waves?
They are vibrations caused by the earthquake and are sent out from the focus
What is the epicentre?
It is the point directly above the focus on the earth surface where seismic waves are strongest.
What are the three types of focus earthquakes?
Shallow focus- 0-70km below surface
Intermediate focus- 71-300km below the surface
Deep focus- 300-700km below the focus
The shallower the earthquake the stronger it is as the seismic waves have less distance to travel to reach the surface
Define aftershocks
Aftershocks are the smaller earthquake that follow the main shock and are caused by vibrations in the rock caused by the initial earthquake.
Where do the most powerful earthquakes occur?
At convergent plate boundaries
What do scientists use to measure seismic waves?
Seismograph
What are seismologists?
Scientists who study earthquake activity
What are P Waves?
-primary waves
-hit first
-travel through liquid, solid and gas
-do not have much energy
-do not cause damage
-push and pull rock
What are S Waves?
-secondary waves
-Only travel through solids
-Much more energy than P waves
-Noticeable as they cause ground to shake
-Crust moves up and down
What are surface waves?
-last to arrive
-travel slowly along the surface
-cause most damage
infrastructure violently sway and collapse
-moves crust up and down + side to side
What is the Richter scale?
Reading from seismographs can be recorded on a Richter scale allowing seismologists to accurately determine the magnitude of the earthquake.
-It begins at 0 an has no upper limit
-It is a logarithmic scale with each step on the scale representing a tenfold increase in magnitude
What is the moment magnitude scale? (MMS)
-It is the most commonly used
-Combines seismograph readings with the amount of rock movement at the fault.
-Uses a logarithmic scale with each step representing a tenfold increase in magnitude
-Considered more accurate than the Richter scale
