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The Australian National University
Research School of Earth Sciences
Earth Physics

Teleseismic tomography uses relative arrival time residuals from distant earthquakes to image wavespeed variations in the upper mantle beneath a seismic array. The code distributed here is unique in that it uses the Fast Marching Method (FMM) to compute traveltimes and paths through the 3-D model. FMM is a grid based eikonal solver that combines computational speed and robustness. The inverse problem is solved using a subspace inversion method which is also fast and robust. The forward and inverse steps can be used iteratively in order to address the non-linear nature of the tomographic inverse problem. Spherical coordinates are used to account for the curvature of the Earth. Like most teleseismic tomography codes, traveltimes from the distant source to the edge of the 3-D model are computed using a global reference model. In our case, we use ak135, although other models could be substituted.

The teleseismic tomography code is written mainly in Fortran 90, although some Fortran 77 code is used for computing ak135 traveltimes. The code has been tested on a number of platforms, and should work on most computers that have acces to compilers distributed by the likes of GNU, NAG, Portland, Pathscale, Intel, Fujitsu and Sun. An extensive instruction manual can be downloaded by clicking on the link below; this manual is also provided with the distribution.

instructions.pdf (1.3 Mb)

To obtain the complete source code, detailed documentation, example input files, and a journal paper (in PDF) which use the code, download the Unix gzipped and tarred file below:

fmtt_v1.0.tar.gz (2.9 Mb)

NEW DISTRIBUTION! Released on 14/01/2008!
(Bug fixes last applied on 05/06/2008)

Changes from previous versions include:
(1) Complete reorganisation of filenames and directory structures has resulted in a more logical, streamlined and user friendly software package.
(2) Data sets from more than one array can be simultaneously inverted for a single 3-D velocity model (useful for sequentially deployed arrays that span a large region).
(3) More efficient application of FMM in some circumstances.
(4) More detailed instruction manual containing two worked examples.

Bug fixes last applied:
(a) Fixed program "aktsurf" so that S-wave incident angles are now correctly calculated. This change does not effect P-wave incident angles. However, note that the aktsurf input file is now modified.
(b) Fixed program "aktsurf" so that it now properly accounts for the option to limit traveltime field computation to array neighbourhood.
(c) Removed "PAUSE" statement in program "subinv" that caused some compilers to issue a warning.

To unpack the contents of this file, type something like:

gunzip -c fmtt_v1.0.tar.gz | tar xvof -


tar -xvzf fmtt_v1.0.tar.gz

at the command prompt. The contents of the tar archive will be placed in the extraction directory. Instructions on how to use the code can be found in docs, along with a journal paper that performs teleseismic tomography with this package.