1997 SEP06 Coal County, Oklahoma Earthquake

Origin time 23:38:01.99 UTC/GMT, Latitude 34.676degrees N, Longitude 96.499degrees W

Magnitude(s): mbLg 4.4

SHORT PERIOD THREE COMPONENT SEISMOGRAMS OF THE 1997 SEP06 OKLAHOMA EARTHQUAKEjl


The above seismograms were recorded at 40 samples per second from GS-13 short
period vertical (sz), N/S (sn), and E/W (se) seismometers in the walk in vault
near Leonard, Oklahoma. The E/W motion was so large that the S phase appears
to have clipped. 

The straight line before P does not indicate zero earth noise. It appears
as a straight line because the large motion from the earthquake caused the
entire seismograms to be scaled down.

EXTREMELY SHORT PERIOD E/W ACCELERATION SEISMOGRAM AND SONOGRAM OF 1997 SEP06 OKLAHOMA EARTHQUAKEjl

The above East-West earth motion seismogram was made from 200 samples/second
produced by a Guralp CMG-1TD seismometer at 830 m depth in the Crosstimbers
borehole. The samples were earth velocty, but they were transformed to earth
acceleration to emphasize higher frequencies (the transformation is fft.
divide by omega, inverse fft).

Unlike the E/W velocity seismogram from a GS-13 seismometer (third down from
top of this page), the Guralp E/W velocity did not clip.

The acceleration spectrogram (color) shows both P and S energy almost up to
90 hertz. There is also a persistent "layer" above 80 Hertz due to waves
scattered from crustal irregularities surrounding Leonard. The higher thinner
layer may be an artefact of processing.

The left hand scale on the spectrogram (color) is in Hertz. The 2200 to
2300 scales on the bottom of both spectrogram and seismogram are arbitrary
seconds from the beginning of an archive file. 

EARTHQUAKE CATALOG INDEX HOME SEISMOGRAM INDEX