Radiative3D: A Code for Radiative Transport in 3D Earth Models

Radiative3D is an open source computer code for radiative transport simulations of seismic events, including earthquakes and explosions described by moment tensors, in 3-D Earth models. It can produce seismogram envelopes and travel time curves from simulated seismometer arrays, or output information representing bulk energy transport throughout the model for volumetric visualization. Radiative3D uses an efficient algorithm for Monte-Carlo simulation of high-frequency elastic wavefield energy transport through models featuring both large-scale structure (larger than wavelength) simulated by deterministic ray tracing, and small-scale structure (wavelength scale and smaller) simulated by a stochastic scattering process. The 3-D models are composed of adjoining model cells inside of which material properties have simple mathematical description. Within cells, the deterministic mechanism implements curved ray paths in linear gradient background media, and the stochastic mechanism implements pseudo-random preferential scattering based on a formulation that computes mean-free-path and scattering cross sections from a characterization of material heterogeneity in which fluctuation of elastic properties are assumed to follow a von Kármán spectrum of scale lengths. Between cells, material properties may be continuous or discontinuous. In the latter case reflections and refractions may occur. At the model's surface, virtual seismometers may be emplaced to record signal channels representative of seismogram envelopes.