NEXD: A Software Package for High Order Simulation of Seismic Waves using the Nodal Discontinuous Galerkin Method

In geophysics numerical simulations are a key tool to understand the processes of earth. For example, global simulations of seismic waves excited by earthquakes are essential to infer the velocity structure within the earth. Furthermore, numerical investigations can be helpful on local scales in order to find and characterize oil and gas reservoirs. Moreover, simulations enable a better understanding of wave propagation in borehole and tunnel seismic applications. Even on microscopic scales, numerical simulations of elastic waves can help to increase knowledge about the behaviour of materials, e.g. to understand the mechanism of crack propagation in rocks. To deal with highly complex heterogeneous models, here the Nodal Discontinuous Galerkin Method (NDG) is used to calculate synthetic seismograms. The advantage of this method is that complex mesh geometries can be computed by using triangular or tetrahedral elements for domain discretization together with a high order spatial approximation of the wave field. The simulation tool NEXD is presented which has the capability of simulating elastic and anelastic wave fields for seismic experiments for one-, two- and three- dimensional settings. The implementation of poroelasticity and simulation of slip interfaces are currently in progress and are working for the one dimensional part. External models provided by e.g. Trelis/Cubit can be used for parallelized computations on triangular or tetrahedral meshes. For absorbing boundary conditions either a fluxes based approach or a Nearly Perfectly Matched Layer (NPML) can be used. Examples are presented to validate the method and to show the capability of the software for complex models such as the simulation of a tunnel seismic experiment.