Exploring Seismoelectric Interface Responses at Poroelastic/Elastic Boundaries: numerical and experimental approaches

Seismoelectric effects, arising from the interaction between seismic waves and electromagnetic fields, have attracted considerable scientific interest for their potential applications in subsurface characterization, geothermal exploration, and hydrocarbon prospecting. While most of previous research has predominantly focused on fluid/poroelastic and poroelastic/poroelastic interfaces, there has been a notable knowledge gap regarding the behavior of seismoelectric signals at poroelastic/elastic interfaces, a crucial aspect in many geological scenarios. This study addresses this gap by providing concrete evidence of interface responses within poroelastic/elastic transitions through experimental measurements of seismoelectric coseismic and interface responses. The experiments were conducted using a plastic container filled with Landes sand as the poroelastic medium, saturated  with NaCl. The container featured distinct interfaces with four different elastic media: glass, plastic, aluminium, and granite, as well as a poroelastic medium (Vosges sandstone) for comprehensive analysis. The experiments were conducted separately for each interface, with specific focus on two different pore fluid conductivities (36 μS/cm and 100 μS/cm). Furthermore, numerical simulations enable a direct comparison between experimental data and theoretical predictions, leading to an excellent agreement between measured and simulated  data in particular regarding the amplitude and polarity of the seismoelectromagnetic signal generated at poroelastic/elastic interfaces. The present demonstration of the electromagnetic signature at poroelastic/elastic boundaries contribute to the overall understanding of seismoelectric phenomena, enhancing the toolkit available to geophysicists and improving the accuracy of subsurface assessments.