Name
Date
Class
Earthquakes and Seismic Waves
Name
Date
Class
Earthquakes and Seismic Waves
1. What are seismic waves? ___________________________________________________
2. In what order do the three types of seismic waves arrive at a seismograph?
_____________________________________________________________________________
3. Which type of seismic wave produces the most severe ground movement?_________________
4. Describe the moment magnitude scale, and explain why it is useful in measuring earthquakes.
_____________________________________________________________________________
_____________________________________________________________________________
5. How do geologists locate the epicenter of an earthquake?
_____________________________________________________________________________
_____________________________________________________________________________
Building Vocabulary
6.
focus
a. records ground movements caused by seismic waves as they
move through Earth
7.
epicenter
b. slowest seismic waves
8.
surface waves
c. the point beneath Earth’s surface at which rock under stress
breaks and triggers an earthquake
9.
seismograph
d. the point on the surface directly above the point at which an
earthquake occurs
Name
Date
Class
Earthquakes and Seismic Waves
Comparing the Richter and Moment Magnitude Scales
The Richter scale rates earthquakes based on the size of their seismic waves, as
measured by seismographs. The moment magnitude scale rates earthquakes based
on the total amount of energy they release. To determine the moment magnitude
rating, seismologists measure the surface area of the ruptured fault and how
far the land moved along the fault. An earthquake’s Richter rating and moment
magnitude rating are not always the same. The table below shows the ratings on
both scales of some famous earthquakes.
Magnitude
Date
Location
1906
1960
Richter scale
Moment
magnitude scale
San Francisco, CA
Arauco, Chile
8.3
8.3
7.7
9.5
1985
Mexico City, Mexico
8.1
8.1
1989
1999
2003
2004
San Francisco, CA
Izmit, Turkey
Bam, Iran
Sumatra-Andaman Islands
7.1
7.4
6.5
9.1
7.2
7.4
6.6
9.3
2005
2008
Pakistan
Eastern Sichuan, China
7.6
8.0
7.6
7.9
1. Which earthquake was strongest according to the Richter scale? __________________________
Which was strongest according to the moment magnitude scale? __________________________
2. Which earthquakes had the same ratings on both scales?________________________________
3. Which earthquake was rated more than 0.5 stronger on the moment magnitude scale than it was
rated on the Richter scale? ________________________________________________________
4. Which earthquakes were rated stronger on the Richter scale than they were rated on the moment
magnitude scale? ________________________________________________________
5. Why can the same earthquake have different ratings on the two scales?
______________________________________________________________________________