Name :
Earthquakes & Tsunamis Notes
Earthquakes
• Sudden releases of _________ through the earth’s
_____________
• The point within the crust where the quake originated
is called the _____________.
• The point on the surface above the focus is the
_______________
• Measured in three ways:
– Richter Scale
– Moment magnitude Scale
– Mercalli Scale
Richter Scale
• Based on the _____________ of the amplitude of
waves on a seismograph
• Logarithmic scale:
• Each number on the scale is ___________ times
more powerful
Moment Magnitude Scale
• Based on _______________ properties of the
earthquake
– ___________ of fault affected
– ___________ the earth moved
– Not based on any seismic readings.
– Can more accurately measure large
earthquakes.
Mercalli Scale
• Measures the intensity based on ________________
and ________________
• Useful in areas where data was not recorded.
• Used worldwide
Earthquakes
• Occur at plate boundaries
• Type of boundary will determine the fault type
• Three main types:
• Normal
• Thrust/Reverse
• Slip-strike
Normal faults
• Land falls ____________ normal
• Occur frequently at _______________ boundaries
• Result in weak, shallow earthquakes
Reverse/Thrust faults
• Land is lifted _____________normal
• Occur frequently at ________________ boundaries
• Cause strong, deep earthquakes
Slip-strike faults
• Land is shifted _______________________
• Occur at ___________________ boundaries
• Cause moderate, shallow earthquakes
Hollister, CA: Aseismic creep
Seismic Waves
• Seismic Waves are waves of energy that travel
through the earth.
• Body waves: travel through the __________
• Surface waves: travel along the __________
P waves
• P waves, or Primary waves, are body waves that
travel through the earth with ______________.
• They are detected first in seismographs
• A drop of water spreads using compression.
S waves
S waves, or secondary waves, are body waves that
travel through the earth using _______________
• Shearing means to stretch something side to side
• They are the second waves detected by
seismographs
Surface Waves
• Surface waves only travel along the earth’s crust, not
through the interior.
• They move the earth up and down
• They are only felt locally
•
•
•
Seismic waves tell us about the interior of the earth.
First, as waves pass through different layers, they will
change ____________ and bend.
Also, S waves cannot travel through ____________.
S waves show us where the boundary for the liquid
outer core is.
Tsunamis
• A tsunami is a wave with a huge _______________,
often several hundreds of miles long.
• Where surface wave’s particle rotation only reaches a
few meters below the surface, the tsunami’s wave
rotation can be felt as deep as the bottom of the
ocean.
• Tsunamis originate at earthquake ______________
at plate boundaries.
• Earthquakes result in the shifting of plate boundaries.
• When this occurs under the ocean, the plate and the
ocean have to _______________
• A Tsunami is created from an area of ocean bottom
being suddenly ______________ up or sinking.
• This will displace the water above it, creating the
tsunami.
• As the tsunami nears land, the beginning trough will
be seen as water _______________ from the
shoreline and heading out to sea.
• After that, the water will begin to __________ until
the wave crest arrives.
• A tsunami acts more like a giant __________ of rising
water than a wave.
• There is a tsunami detection system in place in the
Pacific Ocean.
• It saves millions of lives every year.