#1. A seismogram is a record of the ground motion as recorded from a seismic station.
Below is a seismogram from an earthquake that occurred in Hokkaido, Japan in 2003, as
recorded on a seismograph in W. Lafayette, IN.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
In the image above, label the following features; crest, trough, and one wavelength.
#2 Using your knowledge of waves and some additional information, provided below, we
can calculate the magnitude for this earthquake. The equation to calculate the Surface
Wave Magnitude is:
MS = log10(A/T) + 1.66*log10(D) + 3.3
Where
D = distance from the epicenter to the station measured in degrees, in this case Lafayette,
IN is 86.07 degrees from Hokkaido, Japan
T = period in seconds
A = the displacement amplitude in microns or a/Disamp
a = amplitude in counts
Disamp = the displacement amplification of the recording instrument, in this case 0.63,
What is the magnitude of this event?