is a three-dimensional (3D) modeling and inversion code designed for subsurface imaging and monitoring using static and time-lapse 3D electrical resistivity (ER) or spectral induced polarization (SIP) data. To address the computational demands of inverting large scale 3D and 4D data sets, E4D was designed specifically to run on Linux/Unix-based distributed-memory, parallel, high-performance computing systems. However, E4D will run on any system with at least two processing cores, and can be compiled for Windows-based operating systems using Cygwin, (see installation documentation-Section 3.0). E4D executes by reading a number of user-created ascii text input files, executing a particular run mode (e.g.; mesh generation, ER forward simulation, ER inversion, SIP inversion etc), and reporting results. Run-time options made available through input files are designed to enable flexibility and a high level of customization for a particular problem, making E4D suitable for both advanced research applications as well as more common imaging problems. See capabilities page for further information.

A critical component of E4D is visualization. The E4D distribution includes the utility program bx, which places E4D simulation results into an exodus II finite-element, data-model-formatted file. Exodus II files are then visualized using the VisIt visualization program, an open-source visualization code developed by the Lawrence Livermore National Laboratory. Although E4D documentation focuses on the use of VisIt, all of the files necessary for users to develop and operate other visualization codes are provided by E4D. Guidance concerning the use of VisIt is provided on the VisIt website, and is not provided with the E4D user documentation

The intended audience for E4D includes researchers and other practitioners familiar with electrical geophysical methods and deterministic geophysical inversion. This website provides information concerning capabilities, availability and licensing, download and installation, and quality assurance testing and documentation. Guidance concerning the use of E4D is provided in the E4D Users Guide, which is included with the E4D distribution.