for a lower graphics version
By completing these activities, the learner will:
determine patterns in earthquake locations
use seismograms to measure earthquake magnitudes
investigate seismograms from significant events
locate epicenters using distance/time formulas and procedures
compare and contrast the feasibility of an Earthquake Alert System
occur all over
The vast majority are too weak to be felt; but they can be measured using
of Earthquakes Recorded in the Last 14 Days
As you can see, most of the earthquakes
occuring in the US are in the
portion. This includes:
Although major earthquakes are infrequent, there are also active regions
in southeastern Canada
and in the MississippiValley.
Maps on the Web
are used to measure the magnitude of an earthquake.
This is done by measuring the amount of ground movement. The output of
a seismograph is a seismogram.
Current seismograms can be seen in Los
Angeles, CA, Reno,
NV, and Orange
The three most important parts of a seismogram are:
The difference in arrival times indicates how far away the epicenter is
located. This is because P-waves propogate through the Earth much faster
than S-waves propogate. Note the first P-wave arrival and the first S-wave
arrival as shown on the seismogram below. (Make your own seismogram
by clicking here).
the amplitude of the ground movement
the time of first P-wave arrival
the time of first S-wave arrival
2. Earthquake epicenters are pinponted by at least three stations calculating
the location of a "virtual" earthquake.
3. The shape of the amplitude disturbance also indicates the type of
earthquake. Underground nuclear tests can also be monitored in this way.
Use NIH Image to determine the distance
from the epicenter to each recording station A, B, E, and F.
Read the Earthquake
Alert System background material. This is a feasibility study being
done for the San Francisco, California area. Write an essay explaining
why such a system is necessary in this area, and how successful you think
it will be. Examine a population density map in an atlas along with a map
showing plate boundaries. Make a list of large urban areas that are close
to potentially active plate boundaries.
Explore how tsunami's
are related to earthquakes.