Comparison of full and quasi‐static seismoelectric analytically based modeling

Quasi‐static electromagnetic (EM) approximation was frequently used in numerical modeling of the seismoelectric wavefields, but the computational error it brings is unclear. In this study, we investigate the error caused by the quasi‐static EM approximation based on a horizontally layered model. With such an approximation we obtain a simplified set of Pride's equations and present an analytically based algorithm to solve the seismoelectric responses to an explosive source. First, we solve the seismic wavefields by ignoring the influence of the converted EM fields on the propagation of the seismic waves. Second, we simplify Maxwell equations to a Poisson equation of the electric potential, from which the EM signals are solved. The solved EM signals are compared with the solutions solved from the full Pride's equations to investigate the error caused by the quasi‐static EM approximation. The result shows that the quasi‐static EM approximation causes the loss of the electric field accompanying the S waves and yields errors in modeling the coseismic magnetic fields accompanying the S waves. The errors tend to become smaller when increasing the frequency and decreasing the salinity, implying that the quasi‐static EM approximation seems to be more suitable for simulating the coseismic EM signals under high‐frequency and low‐salinity conditions. The quasi‐static EM approximation also affects the simulation of the interfacial EM waves. Only under the condition that the wavelength of the EM wave is much larger than the source‐receiver distance, the quasi‐static method is valid in simulating the EM wave. Key Points An algorithm with quasi‐static EM approximation is presented to solve the seismoelectric wavefields in a horizontally layered media Seismoelectric wavefields solved with and without introducing quasi‐static EM approximation are compared to analyze the errors Errors caused by quasi‐static EM approximation increase with the decrease of the frequency and the increase of the pore fluid salinity