Earthquakes & Seismic Waves
Seismic Waves Part 1
Name: _______________________________
Date: ________ Pd.: ____
Part A. Class Discussion Notes
Directions: Read each statement. Record the correct response to complete the statement.
Seismic Waves
When there is ____________________ at a fault, _______________ is released:
The shaking occurs as the ____________ travels out from the _____________ in the form of _____________
(like ripples in water).
Focus
1. The ___________ is the _________________________ of an earthquake.
2. It is where the rock actually __________ and motion occurs.
3. Most of the time it is _________________________ (at least 65km down).
Epicenter
1. The spot on ______________________ directly __________ the __________.
2. This spot experiences the _______________________ during the earthquake.
3. After an earthquake, its ____________ given by the ______________ location.
P waves (Like a slinky)
(http://www.wwnorton.com/college/geo/egeo/animations/ch8.htm)
1. Primary waves: Arrive at a location _______________ any other waves.
2. Fastest waves: travel at the _____________________________.
3. Push-pull waves: _______________________________ at rock as it travels through it.
4. Pass through _______________________: travels through magma.
P waves:
Because they travel through liquids and solids, ________________ can ________________ through the
________________________________________ of Earth and affect locations on the other side of Earth.
S waves (Like shaking a rope)
(http://www.thetech.org/exhibits/online/quakes/waves/p&s_waves.html)
1. Secondary waves: Waves that arrive _____________ at a location.
2. Slow waves: travel at the ______________ (about ___ of P waves).
3. Shake waves: vibrate and move ___________________________.
4. Solids-only waves: travels through _________ rock _________.
S waves:
Because they travel through __________________, the S waves do not travel to the other side of Earth. When they
______________________ magma interior of Earth, they _______________.
Surface waves (Like ripples in water)
1. Waves that propagate through Earth’s ________________.
2. They are the _________________ type of waves.
3. THEY ARE THE ________________________________!!!
Seismographs
We measure all of these waves using a _________________________.
1. It draws a ________________ pattern that depicts the seismic ______________.
2. It creates a print out called a _________________________.
By looking at the seismogram, two conclusions can be made.
 Speed of the waves.
 Distance to the Earthquake ____________________.



______________ are ___________ to arrive.
______________ are ___________ to arrive.
______________ waves are ____________ to
arrive.
The_______________________________________ between the S and P waves, the _________________________ the
earthquake epicenter.
Example: Race car racing a station wagon… the longer the race, the larger the distance between the two cars – race call
pulls ahead.
Earthquakes & Seismic Waves
Part 2: Analyzing Seismic Waves
Name: _______________________________
Date: ________ Pd.: ____
Part A: Time-travel graphs
What if you want to find the ______________________________________?
- Use a ______________________________________.
- It shows the average travel times for P and S waves.
1. Find the time between the P and the S wave (either from the
seismogram, or it may be given to you).
2. Use the time-travel graph and find the spot on the graph where the S
and P waves are separate by the time you found in step 1 above.
3. Drop a line straight down at the location and read the distance off the
graph.
Seismic Waves
1. We have never “seen” the ___________________ of Earth, but
waves help show us what is there.
2. The idea that Earth is made of __________________________ and different types of material was
supported by studying the motion of seismic waves.
3. Remember, __________________ pass through __________________________________.
4. ______________________ pass only through _____________________.
Example:


S waves do not travel to the other side of Earth  they cannot get through the liquid mantle.
The denser the substance the wave is traveling through  the faster the wave goes. (We figure out
density of interior Earth).
Triangulation: WHERE is the epicenter?
Suppose you wanted to find the location where the earthquake occurred? Once an earthquake occurs, you
can determine its location.
1. ______________ seismograph stations must pick up the waves.
2. Using the _____________of waves, the station can say that the
earthquake occurred within a certain ____________. (distance)
3. Once 3 stations _________________________________, the
______________________ is where the 3 circles intercept each
other.
Part B. Group Discussion
Directions: Analyze the graph. Read each question. Record your response using the data from the graph.
Seismic Wave Speeds
Seismographs at five observation stations recorded the arrival times of the P and S waves produced by an earthquake.
These data are shown in the graph.
1. What is the dependent variable shown on the x-axis of the graph?
___________________________________________________________
2. What is the independent variable shown on the y-axis?
___________________________________________________________
3. How long did it take the S waves to travel 2,000 km? ______________
4. How long did it take the P waves to travel 2,000 km? ______________
5. What difference in the arrival times of the P waves and the S waves at 2,000
km? _________________________________________________
6. What difference in the arrival times of the P waves and the S waves at 4,000
km? _________________________________________________
Part C. Independent Practice
Identifying Waves
Directions: Analyze and label each picture.
Type of Wave: _________________
A. ________________
B. ________________
C. ________________
D. ________________
Type of Wave: _________________
Name: _______________________________
Date: ________ Pd.: ____
Earthquakes & Seismic Waves
Part 3: Monitoring Earthquakes
Part A. Class Discussion Notes
Directions: Read each statement. Record the correct response to complete the statement.
Earthquake Detector
Scientists have two ways of measuring earthquakes:
 __________________________________
 __________________________________
Richter Scale
1. A scale that measures the _________________ of the largest ___________ recorded on a seismogram.
2. The wave amplitude increases by __________________________ magnitude increase on the scale.
3. Example: A Mag _____ earthquake has waves ____________________________ than a Mag _____.
4. This scale is the most common used to report the strength of an earthquake.
5. The higher the magnitude of the wave, the _____________________ the earthquake.
Mercalli Scale
1. A scale that measures the ______________________________ that occurs after an earthquake.
2. Not very common.
How Does a Seismograph Works?
(http://www.appstate.edu/~marshallst/GLY1101/animations/how_seismograph_works.swf)



A horizontal ________________ paper cylinder connects to the frame.
A heavy weight with an attached ____________________ hanges from the frame.
When an earthquake occurs, the weight and its pen remains fixed in space (inertia) while the
______________ and the __________________ roll are moved by the vibrating ground.
Part B. Group Discussion
Directions: Analyze the graph. Read each question. Record your response using the data from the graph.
Reading a Seismogram
1. In what order did the seismic waves arrive at the seismograph
station? ___________________________________________
2. Which type of seismic wave produced the largest ground
movement? ________________________________________
3. What was the difference in arrival times for the P waves and S
waves? ____________________________________________
4. What would the seismograph look like several hours after this
earthquake? _________________________________________
5. How would the seismograph change if an aftershock occurred?
_____________________________________________________
THE RICHTER SCALE IS A MATHEMATICAL MEASUREMENT OF
THE STRENGTH OF THE GROUND SHAKING.
THE MODIFIED MERCALLI SCALE MEASURES HOW PEOPLE
FEEL AND REACT TO THE SHAKING OF AN EARTHQUAKE.
The shaking is measured by a seismograph.
It is actually a measurement of the height (amplitude) of the
waves produced by the earthquake. Wherever an earthquake is
recorded, it will measure the same on the Richter Scale.
It is based on a series of key responses such as people
awakening, the movement of furniture, and damage to
structures. In general, the further one is from the epicenter of
an earthquake, the less shaking is experienced.
Mercalli
Intensity
(I – XII)
I
II
III
IV
V
VI
VII
VIII
IX
X
XI
XII
Verbal
Description
Instrumental
Feeble
Slight
Moderate
Rather Strong
Strong
Very Strong
Destructive
Ruinous
Disastrous
Very
Disastrous
Catastrophic
Richter
Magnitude
(1 – 10)
1 to 2
2 to 3
3 to 4
4
4 to 5
5 to 6
6
6 to 7
7
7 to 8
8
8 or greater
What Happens?
Detected only by seismographs
Noticed only by sensitive people
Resembling vibrations caused by heavy traffic
Felt by people walking; free standing objects rock
Sleepers awakened and bells ring
Trees sway, damage from overturning and falling objects
General alarm, cracking of walls
Chimneys fall and some damage to buildings
Ground begins to crack, houses begin to collapse, pipes break
Ground badly cracked, many buildings destroyed, some landslides
Few buildings remain standing, bridges and railways destroyed, water,
gas, electricity & telephones out of action.
Total destruction; objects are thrown into the air, shaking and distortion
of the ground