1995 SEP15 Woods County, Oklahoma Earthquake

Origin time 00:31:33.05 UTC/GMT, Latitude 36.870degrees N, Longitude 98.726degrees W

Magnitude(s): mbLg 3.8

SHORT PERIOD VERTICAL AND BROAD BAND VERTICAL SEISMOGRAM OF THE 1995 SEP15 OKLAHOMA EARTHQUAKEjl


The above seismograms were recorded at 20 samples per second from a Geotech
KS54000-0103 seismometer at 119 meter depth in the Glasnost borehole near
Leonard (bz), and at 40 samples per second from a Geotech GS-13 seismometer
(sz) in the walk-in vault near Leonard.

This eight second segment shows clearly three P wave arrivals. Pn was refracted
along the top of the upper mantle, Pb was refracted along the top of the
crust's lower layer (or second layer, or Basaltic layer), and Pg travelled
through the crust's upper layer (or top layer, or Granitic layer). The paths
are shown in the diagram below (the diagram was actually scaled for an
earthquake to station distance of slightly over 200 km.; the earthquake to
station distance of this quake was 284 km.). The three arrivals are very
clear in the bz seismogram. In the sz seismogram (which will show frequencies
up to 16 Hertz; the bz shows only up to 8 Hertz) there appear to be as many
as five to six arrivals. This tells us that the real crust may be more 
complicated than the simple two layers over a mantle. Also one or more of the
arrivals may be reflections.

RAY PATHS OF Pn and Pg for the 1995 JAN18 OKLAHOMA EARTHQUAKE also Pb ray pathjl

BROADBAND VERTICAL SEISMOGRAM OF 1995 SEP15 OKLAHOMA EARTHQUAKEjl

The above broad band vertical seismogram (recorded at 20 samples per second
from a Geotech KS54000 borehole seismometer at 119 meter depth) shows 150
seconds, including P and S arrivals from the 1995 SEP15 Woods County 
earthquake. Three P arrivals are seen as in the seismograms at the top of
this page, but only one label (Pn) for a P phase is shown.

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