Download Notes - Earthquakes 2 - Seismic Waves / HW Questions

EARTHQUAKES II
Earthquakes Release Stored Potential Energy
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When rocks break and an earthquake occurs a significant amount of
_____________________ is released.
The energy travels through Earth in the form of ______________.
These waves are called ____________________.
The waves start in the crust where the rocks break and travel
__________________ in all directions from this point.
This outward traveling energy causes Earthquake ________________.
Focus vs. Epicenter
• ___________:
• The focus is the ____________________ of an earthquake.
• It is where the rock actually snaps and ________________ occurs.
• Most of the time it is __________________ (as least 65 km down).
• ___________:
• The ___________ on Earth’s surface directly ____________ the focus.
• This spot experiences the ___________________ during the earthquake.
• After an earthquake, the earthquakes ___________ is given by the _______________ location.
Seismic Waves
• When there is movement at a fault, energy is released in the form of __________________________:
• The shaking occurs as the energy travels _______ from the ___________.
• Like throwing a stone in a pond, the ripples of water move out in all directions.
• There are two types of waves released
• _________________________ – travel through Earth
• _________________________ – travel on Surface
Seismic Waves – Body Waves
____________:
 A ___________ moving ____________________ body wave that can travel through both
____________ and _____________.
 Because they travel through liquids and solids, P-waves can travel through the liquid and solid interior
of Earth and ________________________ on the _____________________ of Earth.
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P-Waves (Primary – Think _____________)
1. _____________ waves: Arrive at a location before any other wave.
2. _____________ waves: Travel at the highest speed (6km/sec.)
3. _____________ waves: Pushes & Pulls at rock as it travels through it.
4. ___________________ – can travel through magma.
EARTHQUAKES II
Seismic Waves – Body Waves
_____________:
 A ______________ moving body wave that travels at _________________ to the primary wave and
______________________ through ______________.
 Because they travel through solids only, the S-waves _________ travel to the ____________ of Earth.
 When they _________ the _________ magma interior of Earth, they reflect back eventually stopping.
 S-Waves (Secondary – Think ___________________________)
o ________________ waves: Waves that arrive second at a location.
o ________________ waves: Travel at the slow speeds (about ___ of P wave - __________.)
o ________________ waves: Vibrate and move up and down.
o ________________ waves: travel through solid rock only.
Seismic Waves – Surface Waves
• __________ Waves (Think ________________________)
1. Waves that propagate _________________________________
2. Created when ___________________ reach the ____________
3. The surface _________ like an ocean wave.
4. They are the ___________ type of waves.
• Surface waves are the _________________________!
We measure all of these seismic waves using a _________________________
• It draws a __________ pattern that depicts the seismic waves motion.
• It creates a print out called a ______________________.
By looking at a seismogram, two conclusions can be made.
1. _____________________ of the waves.
2. _______________ to the Earthquakes epicenter.
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P-waves are the __________ to arrive
S-waves are the __________ to arrive
Surface waves are the ____________ to arrive
o The _______________ the distance between the
S and P waves, the ______________ the earthquake epicenter.
o Examples: Race car racing a station wagon…the longer the race, the larger the distance
between the two cars
EARTHQUAKES II
What if you want to find the _______________ to an _______________?
• Use a _______________________ graph
• It shows the _____________ travel times for ______________ waves.
1. Find the time _________ the ___ & ___ wave (either from the
seismogram, or it may be given to you).
2. Use the time-travel graph and find the ________ on the graph where
the S and P waves are _____________ by the _____________________
in step 1 above.
3. __________ a _______ straight down at the location and ________ the
____________ off the graph.
What if you wanted to find where the earthquake occurred?
• Once an earthquake occurs, you can determine its location.
• _____ seismograph stations must ___________ the
seismic waves.
• Using the ____________ time of the waves, the station
can say that the earthquake occurred within a certain
_____________ (distance).
• Once 3 stations map out the radius, the ____________
________ is where the 3 circles ____________ each other.
• This is referred to as _______________________:
Commonly used by geologists to find the ______________
of Earthquakes.
HOMEWORK QUESTIONS
1. Identify / label each
diagram
2. What waves always reach a seismograph station first? _____________ Second? _______________
3. Label the P, S, and Surface waves on the seismogram.
4. Was the epicenter closer to station A or station B?___________
Why?
5. At which station was the earthquake felt the most intensity?
6. What was the lag time between the P and S waves at station B (each line represents 5 min. of time)?