“…This problem has also been addressed by the so-called multiscale method for wave equations (Vdovina et al, 2005;Korostyshevskaya and Minkoff, 2006;Engquist et al, 2007;Owhadi and Zhang, 2008;Minkoff, 2008, 2011;Abdulle and Grote, 2011;Chung et al, 2011bChung et al, , 2013Fu et al, 2013;Gao et al, 2013;Gibson et al, 2014). These various approaches to the multiscale problem can be quite different in their underlying principles, but they tend to reach one specific goal, that is, to solve the wave equations on a set of coarsely discretized mesh to approximate the solutions of the wave equations on the finely discretized mesh, and each coarse element may contain finer elements with highly heterogeneous medium properties in space.…”