5.1. Inversion parameters

For each of the experiments conducted, most of the inversion parameters were held constant for consistency. Some of these parameters are include:

octree_mesh

159,772 cells on an underlying base mesh which is 128 x 128 x 64 cells and has a smallest cell size of 30 x 30 x 15 m.

reference model

A uniforom halfspace with a conductivity of 0.001 S/m and a chargeability of 0.0001.

initial model

Same as the reference model

active cells

No topography is used and all model cells are active in this example. So the topography and model active cells are both set to ALL_ACTIVE.

cell weights

No cells weights are used (NO_WEIGHTS)

interface weights

No interface weights are used (NO_FACE_WEIGHTS)

beta

Beta values are set to DEFAULT

alpha’s

Alpha coefficients are: \(\alpha_s = 1E-5, \alpha_x = \alpha_y = \alpha_z = 1\). This corresponds to a length scale of approximately 316 m in all directions.

chifact

1

tol_nl

1E-2

mindm

1E-3

iter_per_beta

2

tol_ipcg

1E-2

max_iter_ipcg

15

reference model change

The reference model is not changed at each beta step (NOT_CHANGE_MREF)

smoothing

The SMOOTH_MOD_DIF option was used in all inversions.

bounds

For the DC data, NO_BOUNDS were applied. For the IP data, a positivity constraint was enforced using constant bounds (BOUNDS_CONST 0 1).