Two-dimensional simulations of the tsunami dynamo effect using the finite element method

Abstract

Conductive seawater moving in the geomagnetic main field generates electromotive force in the ocean. This effect is well known as the "oceanic dynamo effect." Recently, it has been reported that tsunamis are also associated with the oceanic dynamo effect, and tsunami-induced electromagnetic field variations were actually observed on the seafloor. For instance, our research group succeeded in observing tsunami-induced magnetic variations on the seafloor in the northwest Pacific at the time of the 2011 Tohoku earthquake. In this study, we developed a time domain tsunami dynamo simulation code using the finite element method to explain the tsunami-induced electromagnetic variations observed on the seafloor. Our simulations successfully reproduced the observed seafloor magnetic variations as large as 3 nT. It was also revealed that an initial rise in the horizontal magnetic component prior to the tsunami arrival as large as 1 nT was induced by the tsunami. Key Points The first time-domain tsunami dynamo EM simulation was conducted in the world The magnetic signals of the 2011 Tohoku tsunami at NWP were reproduced well A seafloor horizontal magnetic variation preceded the tsunami arrival at NWP ©2013. American Geophysical Union. All Rights Reserved.