Name:
Class day and time:
Web Extras for Chapter 16: Earthquakes
4.
Web extras: Recent earthquakes in your area. How common are earthquakes where you live or where
friends or relatives live? Let’s start by visiting the USGS Hazards Program page (http://earthquake.usgs.gov/)
and clicking on the world map.
a. How many earthquakes took place over the past seven days?
b.
What do the different color symbols indicate?
c.
What is the smallest size indicated by the size of the symbols?
d.
List any continents over the past seven days that had no earthquakes.
e.
Click on Past 8-30 days. Of the continents you just listed in problem 4d, list any that had no earthquakes
over the past 30 days.
f.
Now let’s look at your nation. If you want to examine the U.S., go back to the main page and click on the
USA map. Earthquakes Canada (http://earthquakescanada.nrcan.gc.ca/index-eng.php) focuses on Canada
and Servicio Sismológico Nacional (http://www.ssn.unam.mx/, click on Sismicidad Reciente) covers
Mexico. What are the smallest magnitude earthquakes shown on your map(s)?
g.
Which part of the country has the most earthquakes?
h.
Where was the largest earthquake on the map, and what was its magnitude?
i.
Was there an earthquake in your state or province? If so, what was its magnitude?
If you want to see seismic hazard maps and seismity maps (showing where earthquakes have occurred over
the past 10 or more years) for your state or another country, click on Info by State or Info by
Country/Region on the USGS Earthquake hazards page.
5.
Past earthquake records. Visit http://www.ncedc.org/cnss/ and select Earthquake Maps & Lists, then Maps of
Earthquakes.
a.
In the first row (World Map Mollweide Projection) and fifth column (5 years of records), click on M > 5.0
to see the location of all earthquakes with a magnitude greater than 5.0. Are shallow, intermediate, or deep
focus earthquakes the most common? Which depth range is rarest/least widespread?
b.
Around which ocean are most intermediate and deep earthquakes found?
c.
Go back to the table on the Maps and Lists page and scroll down the Alaska Map row, 5 years of records
column, and click on M > 4.0. Describe how the intermediate and shallow earthquakes are distributed
relative to the string of Alaskan islands known as the Aleutian Islands and to each other.
Web Extras for the Laboratory Manual for Physical Geology by Jones and Jones (McGraw-Hill).
d.
Go to the Western Hemisphere row, 5 years of records, and click on M > 5.0. Find the earthquake focaldepth pattern that is analogous to that seen in Alaska. Describe the location and overall geometry of this
depth-related trend.
e.
If you want a clearer view of these depth-related trends, try these two links:
(1) Magnitude 9.0 earthquake near Honshu, Japan:
http://earthquake.usgs.gov/earthquakes/eqinthenews/2011/usc0001xgp/neic_c0001xgp_c.php
This is the earthquake that struck Japan in March of 2011, causing the devastating tsunami and disabling
nuclear reactors at a power station.
(2) Magnitude 7.6 earthquake along the Kermadec Islands:
http://earthquake.usgs.gov/earthquakes/eqinthenews/2011/usc0004pbm/neic_c0004pbm_c.php
The northeastern corner of New Zealand appears in the southwestern corner of the map.
If you already know something about plate tectonics, you may want to propose an explanation for these
earthquake data. Why do deep earthquakes occur only along deep-sea trenches in a pattern where they start
shallow at the trench and then become progressively deeper moving in only one direction away from the
trench? In all other places on Earth, the foci of earthquakes tend to be less than 35 km deep. (If you
haven’t learned about plate tectonics, leave this space blank.)
Observations such as these earthquake data were crucial clues that led to the development and acceptance
of the theory of plate tectonics, as you will see in the next chapter.
If you want to see some rare old photos of damage from past earthquakes, visit
www.eas.slu.edu/Earthquake_Center, click on Earthquakes, and finally the archive of interest.
6.
How to determine the epicenter and Richter magnitude of an earthquake. If you want to review the skills
you learned in this lab, check out this excellent and highly interactive website:
www.sciencecourseware.org/VirtualEarthquake/.
Web Extras for the Laboratory Manual for Physical Geology by Jones and Jones (McGraw-Hill).