jl
The above seismogram was recorded at one sample per second from a Geotech KS54000-0103 broadband seismometer at 119 meter depth in the Glastnost Borehole near Leonard, Oklahoma. The trace represents vertical ground acceleration. The large M shaped curves are the solid earth tide. Like the Ocean tide, earth tide is caused by the gravitational attraction of the sun and moon. The curves are a band instead of a line, as the constant rise and fall of Ocean generated microseisms is superimposed on the M shaped line which represents earth tide. The two earthquakes listed in the headings are obvious near 11:00:00 JUL06, and left of 00:00:00 JUL06. A third earthquake, near the rightmost peak (right of 13:00:00) was an Ms=4.6 off the coast of Oregon, USA. These earthquakes appear to be spikes because the compressed time scale has "squeezed" their waves together. On seismic analysis software, a part of the trace can be expanded to show the earthquake's individual waves. On this "gif" web image, expansion is not possible.