Effects of groundwater level variations on seismic ground motion

Summary

The mechanical properties of Earth’s uppermost layers are seismically relevant because they can modify seismic waves as they pass through them. These properties may significantly modify the intensity of ground shaking during an earthquake. The relatively common presence of fluids in these layers raises the question of whether they can affect ground motion during earthquakes. In general, seismic ground motion results from the complex interaction of P- and S-waves within the subsurface, and it is certainly influenced by the presence of fluids. This work examines the effects of varying the groundwater level on seismic ground motion by studying the propagation of P- and S-waves through a saturated porous layer over an elastic half-space. Our results show that ground motion due to both types of incident waves is affected by the presence of water, with changes in amplitude and resonance frequency. These results highlight the importance of accounting for fluid saturation in both site characterization and site response.