An excellent educational
tool has been developed to step students through the process of locating the
epicenter of an earthquake and determining its magnitude. This
interactive "Virtual Earthquake" activity is part of a series of
"Geology Labs On-Line." These labs were designed by Gary A. Novak of
the California University at Los Angeles and supported by grants from the US
National Science Foundation and the California State University System.
The learning module nicely steps us through the
analysis and completes the calculations. Please keep track of your
answers along the way so that you can submit them here.
Visit this URL in a separate browser window:
Read through and complete each step.
Choose the Japan region for simulating the earthquake.
What are the three seismic
stations and what are the S-P interval times for each of them?
Convert the three S-P
interval times to distances using the travel-time graph provided.
Compare your calculated
epicenter location with the true epicenter location. Where is the true
epicenter in latitude and longitude?
Use this URL for a site
which will provide latitude and longitude information on any major city in the
.infoplease.com/atlas/latitude-longitude.html"> (Links to
an external site.)
Now we will proceed to
calculate the magnitude of this earthquake. Follow the instructions in
the online module. What are the three S wave amplitudes you measured?
What is your estimate for
the magnitude of the earthquake and how does it compare to the true magnitude?
The National Earthquake
Information Center provides immediate access to information on earthquakes as
they are being recorded. Such a web resource allow us (and many other
geologists) to utilize and interpret data collected across the globe.
Let's learn more about this resource by using a few of its many features. Use
the following URL to link to the NEIC:
.usgs.gov/regional/neic/"> (Links to an external site.)
then click on
"Current Worldwide Earthquake List"
What are the locations of
the five highest magnitude earthquakes to have occurred in the last three days
and what were their calculated magnitudes?
Adjust the settings (the
gear-shaped symbol near the top of the page) to select an interval of 7 days to
view a world-wide map showing location, magnitude and depth.
What geographic area on
the world had the most shallow earthquakes over the last 7 days? Which
geographic area had the most deep earthquakes? Which geographic area had
the strongest earthquakes overall (regardless of depth)?
With respect to your
answers for the previous question, what types of plate boundary (or
non-boundary) is present at each of these three geographic areas? Do each
of these plate boundaries fit with the types of earthquakes which have occurred
Name an earthquake
(according to its location) which has occurred over the last 7 days in a
non-plate-boundary setting. You will need to click on the "Current
Worldwide Earthquake List" and explore the world a little bit to find
one. What might be a possible source for such a non-plate-boundary event?
Finally, we will visit the
University of Washington Seismology Lab website (at .pnsn.org/">http://www.pnsn.org
.pnsn.org/"> (Links to an external site.)
world-renowned website is maintained by the UW Department of Earth and Space
Sciences. This is the first place to check for important updates on
hazard conditions when a local quake has occurred. Click on
"Recent Earthquakes" to view a map showing the magnitudes, locations,
and dates of the earthquakes which have occurred locally over the last two
For the strongest recent
Pacific Northwest earthquake of the last two weeks, what was its magnitude,
time of occurrence, distance from a major city, geographic coordinates, depth
and topographic setting? (You will need to click on the square that shows that
earthquake in order to get this detailed information.)
Below is some web-recorded
data for the Mt. St. Helens swarms from November, 2001. This information
is presented as if it were actually produced on a standard paper-plotted
seismogram, though it has been color-coded for convenience. Let's
practice reading one of these plots:
About how long (in
seconds) did each of these tiny earthquake events last? When (date and
time to the nearest minute) did the largest earthquake occur on this graph?