On the Origin of Source and Receiver Perturbations in Land Seismic Data

Near-surface conditions often vary within land seismic surveys resulting in differences in source strength and signature. Furthermore, discrepancies between closely spaced recordings are also commonly observed. We investigate the origin of these source and receiver perturbations on land seismic data. The source perturbations retrieved show a strong correlation with the moisture content of soil. For frequencies above 40 Hz, explosive sources located in moist-to-wet sediments transmit more than 100 times more energy into the ground than explosive sources located in dry sands. This difference is a result of high absorption rates in the dry sand due to nonlinear deformation in the near-source region, whereas these absorption rates are low for sediments with fluid-filled pores. The receiver terms are determined for vertical component data, and these do not show a significant correlation with the moisture content of the soil. The changes from receiver to receiver are dominant indicating that these are related to the geophone plant itself. However, we could not fit the receiver responses retrieved to the generally accepted damped harmonic oscillator model which describes the geophone-ground coupling. This implies that this model may need to be revised for future land seismic applications.<br><br>