Transcript earthquakes

Earthquakes
• Shaking and trembling of the earth’s crust.
• About 8000 occur every day or one every 11
seconds
• Caused by plates sliding beside each other
• Tsunami - earthquake on the ocean floor: causing
waves to become greater than 20 meters high
A strike-slip earthquake
causes the plates to slide
past one another.
Normal plate movement
is slipping in a downward
motion.
A thrust earthquake occurs
when the plate moves in an
upward motion.
Seismic Waves
• The three main types
of seismic waves are:
P waves, S waves,
and L waves
P Waves
• Primary waves
• Arrive first at the
epicenter
S Waves
• Secondary waves
• Move in up-down
motion
L Waves
• Slowest moving seismic waves
• Travel on top of Earth’s surface
Measuring Earthquakes
• Seismograph-measures and
detects seismic waves
• Richter Scale- a scale that
allows scientists to determine
earthquake strength based
on many readings
• 1-10 levels at which an
earthquake is measured
Above a 6 is very destructive
• Epicenter - aboveground of
origin; most violent shaking
occurs at the epicenter
WHAT INFLUENCES THE AMOUNT OF
DAMAGE AN EARTHQUAKE CAUSES?
- magnitude of the earthquake (how strong and fast the seismic waves are)
- distance of location from epicentre of the earthquake
- type of movement of the plates or along fault
- local soil conditions (loose, solid, flexible, stiff)
- construction type and quality of infrastructure