Weak zones

DES3D supports several ways to define fault-like weak zones that focus deformation in a model.

Multi-segment weak zones (weakzone_option = 4)

For models that require more than one pre-existing fault (e.g., conjugate normal faults or a step-over fault system), use weakzone_option = 4. This option accepts an arbitrary number of planar fault segments, each defined by its own orientation and spatial bounds.

Each segment uses a General_planar_zone formulation with a proper unit-normal, avoiding the tan(azimuth) numerical singularity of the older Planar_zone.

Configuration

weakzone_option = 4
weakzone_num_segments = 2    # number of fault segments

# Segment 0
weakzone_segments_0_azimuth      = 30.0   # degrees from north
weakzone_segments_0_dip          = 60.0   # degrees from horizontal
weakzone_segments_0_x_min        = 50e3   # bounding box x (m)
weakzone_segments_0_x_max        = 150e3
weakzone_segments_0_y_min        = 0.0
weakzone_segments_0_y_max        = 200e3
weakzone_segments_0_depth_min    = 0.0
weakzone_segments_0_depth_max    = 30e3

# Segment 1
weakzone_segments_1_azimuth      = -30.0
weakzone_segments_1_dip          = 60.0
weakzone_segments_1_x_min        = 150e3
weakzone_segments_1_x_max        = 250e3
weakzone_segments_1_y_min        = 0.0
weakzone_segments_1_y_max        = 200e3
weakzone_segments_1_depth_min    = 0.0
weakzone_segments_1_depth_max    = 30e3

See examples/conjugate-faults-3d.cfg for a two-segment conjugate normal-fault setup.

Number of segments

weakzone_num_segments can be set to any positive integer. Add a weakzone_segments_N_* block for each segment index N = 0, 1, ….

Gaussian weak zone initial condition (IC case 4)

initial_weakzone_option = 4 places a planar weak zone whose along-strike width follows a Gaussian envelope in map view. This is useful for localising the initial failure to the centre of the model domain while tapering to zero at the lateral edges.

initial_weakzone_option  = 4
weakzone_azimuth         = 0.0    # strike direction (degrees from north)
weakzone_dip             = 60.0   # dip angle
weakzone_gaussian_width  = 50e3   # half-width at 1/e (m)

See gospl_driver/examples/gaussian-weakzone-3d-with-gospl.cfg for an example that combines this IC with GoSPL surface-process coupling.