Seasonal velocity variations in Greece associated with aquifers

Velocity variations related to water movements in aquifers are relatively unknown, thus, we propose to study the temporal changes of velocity variations of several aquifers in Greece. To this end, the stretching method is applied to the early coda of the autocorrelation functions of 90 permanent stations. These results, complemented by GPS and precipitation studies, indicate that the record of seasonal variations on seismic velocities may originate from two mechanisms: 1) a natural mechanism associated with the filling of the aquifer by precipitation and 2) an anthropogenic mechanism related to groundwater pumping.

Between 1-3s of period, velocity variations can either vary as a function of water supply to the aquifer: increased water leads to a decrease in wave velocity; or record contraction/relaxation of the rocks beneath the aquifer that vary as a function of its recharge.

 

Thus, the investigation conducted in this study allows us to explain all the seasonal variations observed on the dv/vs in Greece between 1-3s of period.