Download Chapter 5 Notes

Chapter 5: Earthquakes
Section 1: What are Earthquakes? (pg 130)


Every day, somewhere on the planet, an _________________________ is happening.
A part of Earth science is _______________________, or the study of earthquakes.
Seismologists are the scientists who study earthquakes.
Where Do Earthquakes Occur?



Most earthquakes take place near the edges of
______________________________________________. Tectonic plates are giant
pieces of Earth’s thin, outer layer.
Tectonic plates move in different
directions and at different
___________________.
Since earthquakes can push, pull, and
slide past each other, there are many
_______________________, or breaks
in the Earth’s crust. Earthquakes occur
along faults.
What Causes Earthquakes?


As tectonic plates push, pull, or slide past
each other,
_______________________ increases along faults near the plate’s edges. Rocks in
the plates _______________________.
_______________________ is the change in the shape of rock. Rock along a fault
deforms in 2 ways:
o ___________________ matter- like a piece of molded clay
o ___________________ matter- like a rubber band
Elastic Rebound


The return of elastically deformed rock to its undeformed shape (back to the shape it was)
is called ______________________________________________.
During elastic rebound, _______________________ is released and travels as
_______________________ waves. The seismic waves cause an
_______________________.
Faults at Tectonic Plate Boundaries

Specific plate motions take place at different plate boundaries. Each motion creates a
particular type of fault that can produce _______________________.
and Fault Types
Plate Motion
Plate Motion
Fault Type
strike-slip fault
reverse fault
Divergent
 _______________________ occurs when two plates slip past each other. Transform
motion creates strike-slip faults, which _______________________ horizontally past
each other.
 Convergent motion occurs when two plates __________________ together.
Convergent motion creates
_______________________ faults, which are
pushed together along reverse faults.
 _______________________ motion occurs
when two plates pull away from each other.
Earthquake Zones

Earthquakes can happen in
__________________________________ along tectonic plate boundaries.
Earthquakes zones are places where a large number of _______________________
are located.
How Do Earthquake Waves Travel?



Waves of energy that travel through the Earth are called
______________________________________________.
Seismic waves that travel through the Earth’s _______________________ are called
body waves. There are two types of body waves: P waves and
____________________.
Seismic waves that travel through the Earth’s surface are called
_______________________. Each type of seismic wave travels differently.
P Waves

Waves that travel through solids, liquids, and gases are called
_______________________ (pressure waves). They are the
_______________________ seismic waves. P waves are also called primary waves,
because they are always the ____________________ waves of
the
earthquake to be detected.
S Waves

Rock can be deformed from side to side. After being deformed from
side to side, the rock springs back to its original position and S
waves are created. _______________________ or shear
waves, are the second-fastest seismic waves. S waves
____________________ travel through parts of the Earth that
are completely ____________________. S waves arrive later
than P waves and are therefore called secondary waves.
Surface Waves


Surface waves move along the Earth’s ____________________ in the upper part of
the ____________________. There are two types of surface waves:
1. Up, down, and around
2. Back and forth
Surface waves travel more _______________________and are more destructive.
Section 2: Earthquake Measurement (pg 136)
Locating Earthquakes


Seismologists know when and where earthquakes begin by using
_______________________, which are instruments located at or near the surface of
the Earth that record _______________________.
When the waves reach a seismograph, the seismograph creates a
_______________________. A seismogram is a tracing of earthquake motion and is
created by a seismograph.
Determining Time and Location of Earthquake

Seismologists use seismograms to find an earthquakes _______________________.
An epicenter is the point on the Earth’s surface directly above an earthquake’s starting
point. A _______________________ is the point inside the Earth where an
earthquake begins.
The S-P Time Method



The simplest method by which seismologists
find an earthquake’s epicenter is the
___________________________.
First seismologists collect several
seismograms of the same earthquake from
different _______________________.
Then, the seismograms are placed on a timedistance graph. The seismogram tracing of the
first P wave is lined up with the P-wave timedistance curve and the first S wave is lined up with the S-wave curve.
The distance of each can be found by reading the _______________________ axis. A
seismologist can then locate an earthquake’s _______________________.
Measuring Earthquake Strength and Intensity

Seismograms can also be used to determine the earthquake’s
_______________________.
The Richter Magnitude Scale

Seismologists use the Richter magnitude scale, also called the
______________________________________, to
measure the strength of _______________________.

______________________________________________created the scale because
he wanted to compare earthquakes by measuring ground motion recorded by
seismograms.
Earthquake Ground Motion


A measure of the strength of an earthquake is called _______________________. The
Richter scale measures the ground motion from an earthquake and adjusts for distance to
find its strength.
Each time the magnitude increases by one unit, the measured ground motion becomes 10
times larger.
Effects of Different-Sized Earthquakes
Magnitude
2.0
Estimated Effects
Can be detected only by seismograph
3.0
4.0
5.0
6.0
7.0
Modified Mercalli Intensity Scale




Can be felt at epicenter
Can be felt by most people in the area
Causes damage at the epicenter
Can cause widespread damage
Can cause great, widespread damage
A measure of the degree to which people feel an earthquake and the amount of damage
caused by an earthquake is called _______________________.
Seismologists use the
________________________________________________________________
to measure earthquake intensity.
An intensity level I describe an earthquake that is not felt by most people. An intensity
level XII indicates total _______________________ of an area.
The effects of one earthquake vary from place to place, any earthquake will have more
than one intensity value. _____________________ values are usually higher near an
earthquake’s epicenter.
Section 3: Earthquakes and Society (pg 140)
Earthquake Hazard

______________________________________________ is a measurement of how
likely an area is to have damaging earthquakes in the future.

An area’s earthquake-hazard level is determined by past and present
_________________ activity. The greater the seismic activity, the
________________ the earthquake-hazard level.
Worldwide
Earthquake
Frequency (Based
Observations since
Descriptor
Major
Strong
Moderate
Light
Very Minor
Earthquake Forecasting

on
1990)
Magnitude
8.0 and higher
7.0-7.9
6.0-6.9
3.0-3.9
2.0-2.9
Average Number Annually
1
800
About 6,200
About 49,000
_______________________ when and where earthquakes will happen and their
strength is difficult. Seismologists have discovered some _______________________
in earthquakes that allow them to make _______________________.
Strength and Frequency

Earthquakes vary in _______________________. The strength of earthquakes is
related to how often they occur.
The Gap Hypothesis


Another method of forecasting an earthquake’s strength, location, and frequency is based
on the ___________________.
The gap hypothesis is a hypothesis that states that sections of active faults that have had
few earthquakes are more likely to be the sites of _______________________
earthquakes in the future.

The areas along a fault where few earthquakes have occurred are called
____________________________________.
Using the Gap Hypothesis


Not all seismologists believe the gap hypothesis is the _______________________
way of forecasting earthquakes.
But sometimes seismologist’s _______________________ of when an earthquake
occurs is very close to where it actually happens.
Earthquake and Buildings


If buildings are not built to withstand earthquakes, then
they can be destroyed.
Today, older buildings in seismically active places, such
as California, are being made more earthquake
_______________________. The process of making
older structures more earthquake resistant is called
_______________________.
Earthquake Resistant Buildings

Architects and engineers use the newest
____________________ to design and
construct buildings and bridges to better
withstand earthquakes.
Are You Prepared For An Earthquake?

Plan ahead so you will know what to do
before, during, and after an
_______________________.
Before the Shaking Starts



First you should _______________________ your home against earthquakes by
putting heavier objects on lower shelves and talking to your parents about having your
home _______________________.
Next, find _______________ places in each room of your home.
Then, make a _______________ with others (family, neighbors, or friends) to meet in
a safe place after an earthquake.
When the Shaking Starts

If you are inside when an earthquake occurs, crouch or lie down under a
________________ or desk in the center of the room.

If you are outside when an earthquake occurs, lie face
down away from ________________, power lines, and
trees and cover your head with your hands.
After the Shaking Stops

Try and calm down as quickly as possible. Then, remove
yourself from immediate _______________________,
such as down power lines and broken glass.