Electromagnetic Fields Induced by Three-Dimensional Short Ocean Waves in a Horizontally Layered Seabed

Abstract

An accurate model is needed to simulate the electromagnetic fields induced by short-period ocean waves to study the influence of the induced fields on the data set of marine magnetotelluric (mMT), marine controlled source electromagnetic (mCSEM), and marine airborne (low altitude) magnetic anomaly detection (MAD). By using a three-dimensional (3-D) linear wave model and directly solving linear equations derived from Maxwell’s equations and boundary conditions of a horizontal layered seabed, we obtained analytical solutions of the six components of the electromagnetic fields induced by three components of the velocity of ocean waves and three components of geomagnetic fields. In addition to horizontal currents induced by the horizontal velocity and vertical geomagnetic field, the contributions from the horizontal current induced by the vertical velocity and horizontal geomagnetic field and vertical current were considered in the governing equations. On the basis of the solutions, we studied how the geomagnetic field and wind fields affect the relationship between the two horizontal components and between the horizontal and vertical components of the electromagnetic fields at the sea surface. We simulated the influence of water depth and wind fields on the distribution of the spectrum and time series of the induced fields by using a typical wave spectrum and directional spectrum. Finally, the possibility of detecting seafloor conductivity structures by using the electromagnetic response of short ocean waves was also discussed.

Keywords

• Electromagnetic fields
• frequency spectrum
• motional induction
• ocean waves
• time series