Separating harmonics in the ground-force signal of a seismic vibratory source

The ground-force signal of a Vibroseis truck is unavoidably contaminated by harmonics. To better characterize the subsurface, the fundamental mode in the ground-force signal is the preferred choice for the cross-correlation with raw seismic data measured in the field. We present a novel, efficient and effective harmonics decomposition method to separate different orders of harmonics in the ground-force signal. Our method first builds a mathematical model to describe different orders of harmonics in the ground-force signal by honoring the physical mechanism behind the harmonics generation, and then retrieves different orders of harmonics by solving overdetermined linear problems in the analytic-signal domain. The success of our method is demonstrated using both synthetic and field data examples.