Time-lapse 4-D resistivity imaging inversion with positivity constraints
Time-lapse resistivity surveys are used to monitor changes in the subsurface. In some situations, it is known that the resistivity will only decrease (or increase) with time. The 4-D ERT smoothness-constrained inversion method, that includes temporal smoothness constraint, has proved to be a robust method that reduces artefacts due to noise. However, in some cases, the time-lapse inverse models mi