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Chapter 8 & 9
Earthquakes and Earth’s Interior and Plate Tectonics
Earthquakes
 An ____________________is the __________ of Earth produced by the ___________
release of energy
 Focus and ________________
• Focus is the point within Earth where the earthquake _______________.
• Epicenter is the __________________ on the surface directly above the ______________.
 Faults
• Faults are _____________ in Earth where ___________________ has occurred.
• General Features of Earthquakes
– Vibrations of Earth_______________ by a sudden _____________ of
_______________
– Associated with ___________________ along _____________________
– Explained by the ________________ tectonics ________________
– _______________ for earthquakes was 1st explained by ______________ – Early
1900’s
– Rocks “___________________” - phenomenon –called elastic
___________________
Cause of Earthquakes
 Elastic Rebound Hypothesis
• Most _________________ are produced by the ____________ release of _____________
energy stored in -___________ that has been _______________ to great forces.
• When the __________________ of the rock is _____________, it suddenly
________________, causing the vibrations of an _________________
Cause of Earthquakes
 ____________________ and Foreshocks
• An aftershock is a _____________ earthquake that ____________ the ____________
earthquake.
• A foreshock is a _______________earthquake that often ____________ a _________
earthquake.
Earthquake Waves
 Seismographs are _____________________ that record earthquake ___________________.
 Seismograms are ______________ of amplified, __________________ recorded ground
motion _________________ by seismographs.
 _________________ – study of earthquake waves
 ___________________ waves are seismic waves that ___________ along Earth’s outer
_______________.
Earthquake Waves
 Body Waves
• ___________________ as P waves or S waves
• P waves
- Are push-___________ waves that push (____________) and pull (____________) in the
____________________ that the waves ________________
- _______________ through ________________, liquids, and ________________
- Have the ___________________ velocity of all ___________________ waves
 Body Waves
• S waves
____________________waves that _______________ along Earth’s __________ layer
- ______________ particles at ______________ angles to the ____________ that they travel –
Called “Shake _______________________”
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Chapter 8 & 9
Earthquakes and Earth’s Interior and Plate Tectonics
- Travel only __________________ solids
- ________________ velocity than P waves
 A _____________ shows all ____________ types of seismic ___________—surface waves,
P waves, and_____________ waves.
Locating an Earthquake
 Earthquake Distance
• The ___________ is located using the ______________ in the arrival ________ between P
and S wave
recordings, which are related to _______________.
 Earthquake Direction
• Travel____________ graphs from three or more __________________ can be used to find the
__________ location of an earthquake _____________________.
 Earthquake Zones
• About _________ percent of the _____________ earthquakes occur in a few
_______________ zones.
Measuring Earthquakes
 Historically, _________________ have used _________ different types of measurements to
describe the ____________ of an earthquake—_____________ and magnitude.
 ________________ Scale
• Based on the ____________________ of the largest ________________ wave
• ______________ unit of Richter ____________________ equates to roughly a 32-fold
_____________ increase
• Does not ____________________ adequately the ____________ of very ___________
earthquakes
 Momentum Magnitude
• Derived from the _____________ of ________________ that occurs along the
_____________ zone
• _____________ magnitude is the most widely used __________________ for earthquakes
because it is the only magnitude ______________ that estimates the _____________ released by
earthquakes.
• _____________________ very large _________________
Seismic Vibrations
 The ___________________to buildings and other structures from _____________ waves
depends on several ____________. These factors include the _________________ and duration
of the vibrations, the nature of the _______________ on which the structure is
_______________ and the design of the ________________.
 Building Design
• _________________________that determine __________________ damage
- _______________________ of the earthquake
- Unreinforced stone or ___________________ buildings are the most ____________ safety
threats
- Nature of the __________________ upon which the ________________ rests
- The _________________ of the ______________________
 Liquefaction
• __________________- material turns __________________
• _________________ objects may __________ to ______________
Tsunamis
 _________ of Tsunamis
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Chapter 8 & 9
Earthquakes and Earth’s Interior and Plate Tectonics
• A tsunami __________________ by an earthquake occurs where a ___________ of the ocean
floor is ________________ vertically along a fault.
• A____________ also can occur when the ____________ of a quake sets an
_________________ landslide into __________.
• Tsunami is the Japanese word for “_____________ sea wave.”
 Tsunami Warning System
• ___________________ earthquakes are reported to __________________ from Pacific
seismic _____________________.
• Although _______________ travel quickly, there is __________________ time to evacuate all
but the area ___________________ to the ________________.
Other Dangers
 Landslides
• With many _____________________, the greatest _____________to structures is from
landslides and ground _____________________, or the sinking of the ground triggered by
________________.
 Fire
• In the San Francisco earthquake of ____________, most of the _______________ was caused
by_______________ that started when gas and ___________ lines were cut.
___________________ Earthquakes
 Short-Range Predictions
• So far, ________________ for short-__________________ predictions of earthquakes have
not been ___________________.
 ________________-Range Forecasts
• Scientists don’t yet understand enough about how and where __________________ will occur
to make ___________________ long-term _____________________.
• A seismic ____________ is an area along a ___________ where there has not been any
_________________ activity for a ___________ period of ______________.
Earth’s Major Roles
 According to the plate tectonics theory, the ___________ mantle, along with the overlying
crust, behaves as a strong, _________ layer. This layer is known as the ____________.
• A plate is one of numerous _______________ sections of the lithosphere that move as a unit
over the _______________ of the ___________________
Types of Plate Boundaries
 Divergent boundaries (also called _____________ centers) are the place where two
____________ move apart.
 Convergent boundaries form where ____________ plates move ____________.
 Transform fault boundaries are ___________ where two plates grind past each other
without the __________________ or destruction of the ___________________.
Divergent Boundaries
 _________________Ridges and Seafloor _______________
• Oceanic ridges are continuous elevated zones on the floor of all _____________ ocean basins.
The rifts at the ______________ of ridges represent _____________ plate boundaries.
• Rift valleys are deep _____________ structures found along the axes of divergent plate
boundaries. They can develop on the ________________ or on land.
• Seafloor spreading produces new _______________ lithosphere.
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Chapter 8 & 9
Earthquakes and Earth’s Interior and Plate Tectonics
Convergent Boundaries
 A subduction zone occurs when one oceanic _____________ is forced down into the mantle
beneath a _______________ plate.
 Oceanic-Continental
• ________________ oceanic slab ________________ into the asthenosphere.
• Pockets of ____________ develop and rise.
• Continental volcanic arcs form in part by _______________ activity caused by the
subduction of ____________ lithosphere beneath a _________________
• Examples include the Andes, Cascades, and the Sierra Nevadas.
 Oceanic-Oceanic
• _____________ oceanic slabs _______________ and one descends beneath the other.
• This kind of _________________ often forms _________________ on the ocean floor.
• Volcanic island arcs form as volcanoes emerge from the _________.
• Examples include the Aleutian, Mariana, and ________________ islands.
 Continental-Continental
• When __________________ plates contain continental material, two continents collide.
• This kind of boundary can produce new ____________ ranges, such as the Himalayas.
Transform Fault Boundaries
 At a transform fault boundary, plates ________ past each other without ____________ the
lithosphere.
 Transform faults
• Most __________two segments of a mid-ocean ridge.
• At the time of formation, they roughly _______________ the direction of plate movement.
• They aid the movement of ____________ crustal material.
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