To better assess quality of 3D tomographic images and to better define possible impro~~ments to tomographic inversion procedures, one must consider not only data quality but also apprQpriateness of model parametrization and display of results, as well as numerical precision of forward and inverse solvers. Resolution and quality assessment in local-source tomography was the topic of two recently completed PhD theses within the working group. The main results of the working group have been presented at several international conferences and in publications currently in the review process and are summarized in the form of the software package 3DTOMOVE$ available on ANONYMOU8 FTP account on machine tele.ethz.ch (129.132.1Z7.i5) in the directory Ipub/TOMOVES. Alternatively, the software may also be downloaded from the internet page
http://www.sg.geophys.ethz.ch~aesiThis software package for seismic tomography with local sources travel time data has been developed by several authors -see README files and source code headers- and continues to evolve. The package contains source codes, example files, and short descriptions of the' four FORTRAN programs VELEST, SIMULPSI4, FATOMO, and TOMO2GMT. VEL~8T allows to obtain an iterative solution to the coupled hypocenter-1 D-velocity model problem (and joint hypocenter determinations), and is mostly used for the calculation of a Minimum I D model with station 'delays for high-precision earthquake location and for use as initial reference model in 3D-tomog'raphy'. SIMULPSI4 is a special version of 8IMULPS (original code by Cliff Thurber and Donna Ibberhart-Phillips, addition of Farra-and-Virieux-ray tracer by Florian Haslinger, for references see program descriptions) and provides an iterative solution to the coupled hypocenter-3D velocity problem. This version includes the original approximative raytracer and, in addition, a precise shooting ray tracer. FATOMO again provides an iterative solution to the 3D-velocity problem (version 10 by Stephan Husen, solving the velocity part of the coupled problem and using SIMULPS to solve the hypocenter part of the coupled problem) using the fat ray concept. TOMO2GMT 'is a reformatting routine preparing output by SIMULPS and FATOMO for plotting with GMT commands. In' particular, it allows to display honz.~ntal and vertical cross sections of tomographic results (relative or
e~~im.tes~nw- ~h#s~4~ w- ~ resolution diagonal elements, resoluUon spread, etc.).
