Developed by Shinji Toda (DPRI/Kyoto Univ.), Ross Stein & Volkan Sevilgen (USGS, Menlo Park), and Jian Lin (WHOI), is intended both for publication-directed research and for college and graduate school classroom instruction. The authors believe that one learns best when one can see the most and can explore alternatives quickly. So the principal feature of Coulomb is ease of input, rapid interactive modification, and intuitive visualization of the results. The program has menus and check-items, and dialogue boxes to ease operation. The internal graphics are suitable for publication, and can be easily imported into Illustrator, GMT, Google Earth, or Flash for further enhancements. Coulomb is a MATLAB application and so runs on all computers. The software, tutorial files, and a 56-pg full-color user guide can be freely downloaded.
Coulomb is designed to let one calculate static displacements, strains, and stresses at any depth caused by fault slip, magmatic intrusion or dike expansion/contraction. One can calculate static displacements (on a surface or at GPS stations), strains, and stresses caused by fault slip, magmatic intrusion or dike expansion. Problems such as how an earthquake promotes or inhibits failure on nearby faults, or how fault slip or dike expansion will compress a nearby magma chamber, are germane to Coulomb. Geologic deformation associated with strike-slip faults, normal faults, or fault-bend folds is also a useful application. Calculations are made in an elastic halfspace with uniform isotropic elastic properties following Okada . Processes not included in Coulomb are also important, such as dynamic stresses, pore fluid diffusion, and viscoelastic rebound. Further, basins and crustal layering modify the stresses in comparison to the elastic halfspace implemented in Coulomb. Nevertheless, we believe that a simple tool that permits exploration of a key component of earthquake interaction has great value for understanding and discovery.