FWNA

Author:
Ilaria Mosca

FWNA is a package of Fortran programs based on a Monte Carlo approach for solving a waveform inversion and thus defining the 1D physical properties of smallscale structures.
FWNA
Project Description
FWNA is a package of Fortran programs based on a Monte Carlo approach for solving a waveform inversion and thus defining the 1D physical properties (e.g., shear wavespeed, compressional wavespeed, shear dissipation factor) of smallscale (i.e., from millimetres to few meters) structures.
It consists of three main ingredients:
 The programs for solving the inverse problem using the Neighbourhood Algorithm (NA), a Monte Carlo technique developed by Sambridge, [2] and [3] (rses.anu.edu.au/~malcolm/NA/).
 The programs for solving the forward modelling using the package GEMINI II.
 Fortran codes to connect the input/output files of NA and GEMINI with each other.
From a theoretical point of view, the NA samples the entire model space and attributes a misfit function to each solution compatible with the data (top panel of Figure). For each sampled model the algorithm solves a forward problem which in the present case is given by the approach of Friederich & Dalkomo [1]. Then, all the models are expressed in terms of (Gaussian or nonGaussian) probability density functions (pdfs) which represent all the possible information gained from the data (bottom panel of Figure).
References:
[1] W. Friederich & J. Dalkolmo (1995). Complete synthetic seismograms for a spherically earth by a numerical computation of the Green's function in the frequency domain  Geophys. J. Int., 122, 537550
[2] M. Sambridge (1999a). Geophysical inversion with a neighbourhood algorithms I  Searching a parameter space  Geophys. J. Int., 138, 479494.
[3] M. Sambridge (1999b). Geophysical inversion with a neighbourhood algorithms II  Appraising the ensemble  Geophys. J. Int., 138, 727746.