Coulomb 3.3 software
The rationale and philosophy of this software
We 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 MATLAB 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. The USGS publishes the finite fault models of large earthquakes in Coulomb .inp format, making it easy to go deep quickly.
Who is it for?
Coulomb is intended both for publication-directed research and for university classroom instruction. Coulomb is designed to let one calculate static displacements, strains, and stresses at any depth caused by fault slip, magmatic intrusion, or dike expansion or contraction. One can calculate static displacements (on a gridded surface or at GPS stations), strains, and stresses caused by fault slip, magmatic intrusion, or dike expansion.
Stress imparted by the 1995 M 6.9 Kobe, Japan, shock to surrounding mapped faults
What does it do?
How an earthquake promotes or inhibits failure on nearby faults, or how fault slip or dike expansion will compress a nearby magma chamber, are problems germane to Coulomb. Exploring geologic deformation associated with strike-slip faults, normal faults, or fault-bend folds is also a useful application. There is substantial evidence to support the hypothesis that faults interact by the transfer of stress, both on the time scales of earthquake sequences and aftershocks, and on longer time scales associated with the interevent time of the largest shocks that occur in a given region. There is also evidence that faults and magmatic systems also interact, and that static stress changes influence intrusions and eruptions.
Control panels make it easy to explore the stress patterns on the fly and make compelling graphics
How widely has it been used?
The Coulomb software has been used in 10,000 journal publications. Coulomb calculations are made in an elastic halfspace with uniform isotropic elastic properties, following Okada (1992). Processes not included in Coulomb are also important, such as dynamic stresses carried by seismic waves, pore-fluid diffusion, and viscoelastic rebound. Further, elastic stiffness differences between basins and bedrock, and crustal layering modify, the stresses in comparison to the elastic halfspace implemented in Coulomb. Nevertheless, we believe that a simple, flexible tool that permits exploration of a key component of earthquake interaction has great value for understanding and discovery.
Two ways to visualize vertical deformation associated with a left-lateral strike-slip fault
Coulomb was developed when Shinji Toda was at DPRI/Kyoto University, Ross Stein and Volkan Sevilgen were at the USGS, and Jian Lin was at WHOI. Now, Ross and Volkan are at Temblor, which is where you can access the software; Shinji is at IRIDeS/Tohoku University, and Jian Lin is at the Southern University of Technology (SUSTech) in Shenzhen, China.
