What’s new in Coulomb 3.0?

Coulomb now runs on Mac, PC, and Unix computers: The program is very fast on a PC, has not yet been tested on the Vista operating system. For Mac, the operating system must be OS 10.X and later.

Matlab 7.1 or higher is required to run Coulomb. Coulomb 3.0 is now a Matlab (www.mathworks.com) application, so you will need to install Matlab on your computer first. Other than Matlab, you only need a text editor (such as Word, BBEdit or Notepad) and a spreadsheet (Excel).

Many features were added or enhanced in Coulomb 3.0:

• You can now use latitude/longitude directly in the input and output files, and can now add active fault traces, coastlines, and earthquakes from online catalogs, websites, or Coulomb-bundled files. These overlays can then be included compactly in the saved input files in .mat (Matlab binary) format so they automatically plot when the input file is re-run.

• Stress changes can be resolved on faults in their individual rake directions, or on specified rakes. Resolved stress changes can be viewed graphically in 3D or output to tables. Shear and normal stress changes can also be imaged, and the friction can be changed on the fly. Draped wireframe and 3D deformation graphic outputs can be spun and tilted.

• The Coulomb output files can now be exported automatically to Google Earth. This is implemented by using the ‘coulomb2googleearth’ plug-in.

• You can use comprehensive moment centroids and MW to quickly create input faults with lengths, widths, and slip scaled by empirical relations. The slip on these sources can then be easily tapered for more realistic stress distributions.

• Any of the 150 variable-slip source models for earthquakes in Martin Mai’s SCRMOD online database can be loaded into Coulomb as input files.

• Active fault files for California, Japan and Turkey (both Le Pichon et al and Armijo et al interpretations of the Marmara sea faults) are included. Earthquake catalogs in any of 14 formats can be filtered from websites and loaded into Coulomb. You can now graphically plot the Coulomb stress imparted to earthquake nodal planes.

• The 1377-patch Fault-Section Database (part of the USGS-California Geological Survey California Reference Geologic Fault Parameter Database) is included as a Coulomb input file in three formats. These files supply all geometrical features needed to use the database faults as sources or receivers, including the top and bottom of each fault patch, the patch slip rate and rake. The fault network can be used to find the stress change caused by any earthquake on the known surrounding faults given their presumed rakes, and it can be also used to implement simple interseismic stressing by using the sources as virtual dislocations, which uses negative slip rates times the time period to get stress. Use ‘CA_fault_database_slip_rate.mat’ to plot the fault slip rates or to use the sources as virtual dislocations for interseismic stressing. To resolve the stress imparted by an earthquake source on each receiver faults given the rake of each fault, use ‘CA_fault_database_rake.mat’. If you want to use the receiver faults and choose a common rake, use ‘CA_fault_database_noslip.mat’. Note that these are large files and take a long time to run.

• The 'Keys to the City' page has been augmented and illustrated (Sec 2.1).

• You can now make quick, interactive changes to reposition or change parameters of a fault, to change the grid study area, and to toggle between lat/lon and cartesian coordinates (4.3)

• The Kode and corresponding meaning of the two 'slip' parameters (rt.lat/reverse, rake/netslip, lat.slip/tensile opening, rt.lat potency, dip potency, etc) now appear when one selects the 'Open & edit input file' (4.6)

• The seismic moment and Mw of the source fault now appears in command window whenever an input file is loaded. If there are multiple faults, the summed moment appears (4.9)

• Martin Mai's SRCMOD variable-slip database of 150 quakes can now be read by Coulomb and transformed automatically into input files (4.12)

• We now provide a fuller explanation of the role of the receiver fault geometry in Coulomb modeling (7.2)

• We have added Kode 400 point shear sources for small quakes or curved faults (8.3)

• We now discuss the numerical output file for the 'Calc. Stress on faults' option (9.6)

Merging variable-slip sources to one input file (‘merge_input_file’ plugin) (User Guide Sec. 4.13), Making smoothed seismicity density plots (5.5), User-selected contour intervals (6.7 and 7.6), Using the strike/dip/rake/friction slider in the Stress control panel (7.2), Active fault files for the western US, Japan, and Turkey (with a readme file references) are now included.