  Two novel methods, one that is experimental and the other comprising a pair
of theoretical types (one component that is mathematically rigorous and the
other that is of frequency domain computational type), are being used in
concert to study the motion of the Earth at periods in the neighborhood of 1000
s to beyond 10,000 s. Corresponding to frequencies lower than what is routinely
measured by commercial seismographs, our observations are yielding new insights
into the mysteries of Earth dynamics responsible for earthquakes.
