DIRECT P-WAVE SEISMIC NOISE INTERFEROMETRY FOR GROUNDWATER MONITORING: A MODELLING STUDY

In this study, we monitor the depth variation of an unconfined aquifer by applying seismic noise interferometry to synthetic data modelled with a 2D finite-difference software. We consider two models with the same subsurface geological structure, but with different water table levels representing two monitoring periods. The receivers are placed at the topographic surface and collect the seismic signals generated by a source located at the bottom of the aquifer to simulate a pumping system. First, cross-correlation of seismic traces with a reference one is used to produce interferograms (i.e., virtual surveys) for both the tested models. Then, direct P-wave arrivals identified in the two interferograms are compared through the stretching technique in order to estimate the relative velocity changes (dv/v). Finally, the estimated dv/v values are related to theoretical ones obtained using a reference subsurface model to produce the water level depth in the considered monitoring period.