quantitative seismology theory and methods modern global
\partial t^2} = (\lambda + 2\mu) \nabla (\nabla \cdot \mathbf{u}) - \mu \nabla \times (\nabla \times \mathbf{u}) + \mathbf{f} \] where: \(\rho\) is the density, \(\mathbf{u}\) is the displacement vector, \(\lambda, \mu\) are Lamé parameters, \(\math