Download Features of Earthquakes

Features of Earthquakes
Seismic Waves
 ________________________ waves, produced by
_________________________________ are very similar to waves
that you can produce by shaking a rope up and down.
 __________________________ waves travel through the
______________________________.
 During a strong earthquake the ground moves
______________________________ and backward, heaves up and
down, and ________________________ from side to side.
 The ______________________________ of the ground can
_____________________________ likes waves do in water.
Origin of Seismic Waves
 The ______________________ that is produced when rocks
stretch and break builds up and is
_____________________________ when the elastic limit is
reached.
 This __________________________ is in the form of
_____________________________ waves.
 The point where this ____________________________ is first
released is called the _______________________ of the
earthquake.
 The foci of most ____________________________ are within 65
km of Earth’s __________________________.
 A few have been ______________________________ as deep as
____________________.
 ______________________________ waves are produced and
travel outward from the __________________________ focus.
Primary Waves
 When ______________________________ occur, three different
types of _________________________ waves are produced.
 All of the waves are ___________________________ at the same
time, but each behaves differently within ________________.
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Primary waves cause __________________________ in rocks to
move back and forth in the __________________________
direction that the waves is traveling.
Secondary and Surface Waves
 ____________________________ waves move through Earth by
causing ______________________________ in rocks to move at
right angles to the direction of wave travel.
 ____________________________ waves cause most of the
destruction resulting from _________________________.
 Surface waves move rock particles in a
________________________________, rolling motion and a sideto-side _________________________ motion.
 Many buildings are unable to ________________________ intense
shaking because they are made with _______________________
materials.
 The buildings fall apart when ________________________ waves
cause different parts of the building to move in different directions.
Secondary and Surface Waves Cont.
 _____________________________ waves are produced when
earthquake __________________________ reaches the surface of
the Earth.
 _______________________________ waves travel outward from
the ______________________________.
 The earthquake ________________________ is the point on
Earth’s surface directly above the earthquake
_______________________.
Locating an Epicenter
 Different _______________________________ waves travel
through Earth at different __________________________.
 ______________________________ waves are the fastest,
secondary waves are ____________________________, and
surface waves are the slowest.
 ______________________________ have learned how to use the
different speeds of seismic waves to determine the distance to an
_____________________________ epicenter.
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When an __________________________ is far from a location, the
primary wave has more time to put distance between it and the
___________________________ and surface waves.
Measuring Seismic Waves
 _________________________ waves from earthquakes are
measured with an instrument known as a
__________________________________.
 ________________________________ register the
_____________________________ and record the time each
arrived.
 Seismographs consist of a ________________________ drum of
paper and a ________________________ with an attached pen.
 When seismic waves reach the ________________________, the
drum vibrates but the _____________________________ remains
at rest.
 The ____________________________ pen traces a record of the
vibrations on the moving __________________________ of paper.
 The _________________________ record of the seismic activity
is called a ________________________.
Seismograph Stations
 Each type of ______________________ wave reaches a
seismograph station at a different _________________ based on
its speed.
 ______________________ waves arrive
______________________ at the station, and
_________________________ waves, which travel slower, arrive
__________________________.
 Because ______________________________ waves are the
slowest, they arrive ____________________________.
 The difference in __________________________ times is used to
calculate the distance from the seismograph station to the
_____________________________ epicenter.
Seismograph Stations Cont.
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Of ________________________ waves reach three or more
seismograph stations, the location of the
___________________________ can be determined.
To locate an __________________________, scientists draw
_________________________ around each station on a map.
The _________________________ of each circle equals that
stations distance from the __________________________
epicenter.
The point where all _____________________ circles intersect is
the location of earthquake _______________________.
Basic Structure of the Earth
 The ______________________ of the Earth is the core ad it is a
solid, dense material, made mostly of ______________________
with small amounts of nickel, oxygen, silicon, and sulfur.
 _____________________________ from the layers above causes
the inner core to be ________________________.
 Above the solid ________________________ core lies the liquid
outer core, which is also made of mostly
______________________.
 Earth’s _________________________ is the largest, or
_____________________________ layer, lying directly above the
outer core.
 It is made mostly of _______________________, oxygen,
magnesium, and _____________________.
 The mantle is often divided into an ________________________
part and a lower part based on changing
_____________________________ waves speeds.
 A portion of the upper __________________________, called the
________________________________, consists of weak rock
that con flow slowly.
Earth’s Crust
 The ____________________________ layer of the Earth is the
_____________________________.
 Together the ______________________ and a part of the upper
mantle just beneath it make up the Earth’s
__________________________________.
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The ________________________ is broken into a number of plates
that move over the ____________________________ beneath it.
The ___________________ of Earth’s crust _________________.
It is more than 60km thick in some __________________________
regions and less than 5km thick under some parts of the
________________________.
Compared to the _________________________ the crust contains
more silicon and aluminum and less _________________________
and iron.
Earth’s ____________________________ is generally less
____________________________ than the mantle beneath it.
Mapping Earth’s Internal Structure
 As you just learned, the ____________________________ and
paths of seismic waves changes as they travel through materials with
different _______________________.
 By studying __________________________ waves that have
traveled through Earth, scientists have identified different
____________________________ with different densities.
 In general the _________________________ increase with depth
as pressure ________________________.
 Studying ______________________________ waves has allowed
scientists to map Earth’s _____________________________
structure without being there.
Layer Boundaries
 _____________________________ waves speed up when they pass
through the bottom of the ________________________ and enter
the upper mantle.
 This __________________________ between the crust and the
upper mantle is called the
__________________________________ discontinuity or Moho.
 The mantle is _____________________________ into layers
based on changes in seismic wave ________________________.
 For example, _____________________________ and secondary
waves slow down again when they reach the
_________________________________.
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Then they generally speed up as they move through a more
____________________________ region of the mantle below the
__________________________________.
The ______________________ is divided into two layers based on
how _________________________ waves travel through it.
_____________________________ waves do not travel through
the _____________________________ core.
__________________________ waves slow down when they reach
the outer core, but they speed up again upon reaching the
______________________________ inner core.
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