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 crosscorrelation with the raw seismic data measured in the field. We develop a novel, efficient, and effective harmonics decomposition method to separate the different orders of harmonics in the ground-force signal. Our method first builds a mathematical model to describe the different orders of harmonics in the ground-force signal by honoring the physical mechanism behind the harmonics generation and then retrieves the different orders of harmonics by solving overdetermined linear problems in the analytic signal domain. The success of our method is demonstrated using synthetic and field data examples.