Fault_set

Contents

Data Structure: Fault_set
Description	Fault set data structure
Usage	Fault_set NUM=ival where ival is the data structure number

Description

Overview

Fault_set data structure defines a fault set with topology defined by either a single or two Geometry_set or via a Part_geometry_set if the fault is not initially discretised. Fault sets are required for operations of fault seeding or fault insertion.

Name Name of the fault set

Usage

Name

Character Name

Description

Name of the fault set (Maximum of 32 characters).

Fracture_assignment Name of the Fracture_data

Usage

Fracture_assignment

Character Name

Description

Name of the Fracture_data (Maximum of 32 characters).

Description Description of the fault set

Usage

Description

Character Name

Description

Description of the fault set (Maximum 128 characters).

Update_data_flag Flag for updating the data for an existing fault

Usage

Update_data_flag

Integer Value

Description

Flag for updating the data for an existing fault. For example, to indicate that the top surface should be included or not in the contact definition for a particular analysis stage. The valid values are:

• 0 - Data definition is new or overwrites an existing fault definition

• 1 - Data definition updates an existing fault

Fault_type The type of fault in terms of vertical offset

Usage

Fault_type

Character Name

Description

The type of fault in terms of vertical offset; i.e. whether the fault is a normal fault or an inverse fault. This is only required when the output from a restoration will be used as input for a forward model generation. In this case, when there is no pre-existing sediment, the type of the fault will be used to establish whether the geometry associated with faults intersecting the basal horizon is associated with the footwall or the hanging wall. Valid types are:

• "Normal" - Normal fault in extension

• "Inverse" - Inverse fault in compression

Geometry_set Geometry set name

Usage

Geometry_set

Character Name

Description

Assigns the geometry set (or part geometry set) defining the fault. Geometry_set is used for cases where a single geometry (or part geometry) set is sufficient to define the fault. For cases where the footwall and hangingwall surfaces need to be defined separately Footwall_set and Hangingwall_set will be used instead.

Footwall_set Footwall set name

Usage

Footwall_set

Character Name

Description

Assigns the geometry set (or part geometry set) defining the fault Footwall. Definition of Hangingwall_set is also required. For cases where a single geometry (or part geometry) set is sufficient to define the fault Geometry_set might be used instead.

Hangingwall_set Hanging wall set name

Usage

Hangingwall_set

Character Name

Description

Assigns the geometry set (or part geometry set) defining the fault Hangingwall. Definition of Footwall_set is also required. For cases where a single geometry (or part geometry) set is sufficient to define the fault Geometry_set might be used instead.

Property_name Contact property set name

Usage

Property_name

Character Name

Description

Assigns the contact property set (by name) to be applied to the fault. This is only required if the fault set is assigned a different contact property set to the default value.

Footwall_tip_node Node defining the tip of the footwall surface (2D only)

Usage

Footwall_tip_node

Integer Value

Description

Node defining the tip of the footwall surface (2D only). If not specified then the tip is assumed to correspond to the end node of the footwall that has the highest elevation (Y-coordinate).

Hangingwall_tip_node Node defining the tip of the hanging wall surface (2D only)

Usage

Hangingwall_tip_node

Integer Value

Description

Node defining the tip of the hanging wall surface (2D only). If not specified then the tip is assumed to correspond to the end node of the hanging wall that has the highest elevation (Y-coordinate).

Footwall_tip_point Point defining the tip of the footwall surface (2D only)

Usage

Footwall_tip_point

Integer Value

Description

Point defining the tip of the footwall surface (2D only). If not specified then the tip is assumed to correspond to the end point of the footwall that has the highest elevation (Y-coordinate).

Hangingwall_tip_point Point defining the tip of the hanging wall surface (2D only)

Usage

Hangingwall_tip_point

Integer Value

Description

Point defining the tip of the hanging wall surface (2D only). If not specified then the tip is assumed to correspond to the end point of the hanging wall that has the highest elevation (Y-coordinate).

Insertion_type Type of fault to be inserted

Usage

Insertion_type

Character Name

Description

Faults may be either pre-defined via geometry lines (2D) or surfaces (3D) that are grouped into the hangingwall and footwall geometry sets, or generated during the simulation via Fault_insertion. If Fault insertion is specified then individual faults can be assigned a specific fault insertion type. Valid values are:

• "None" - Fault is not inserted into model

• "Default" - Fault insertion will be governed by the settings specified in Fault_insertion

• "Seeded" - Seeded fault, generate one geometry set per line

• "Split" - Split geometry faults, group lines on same fault under same geometry set (2D only)

Mesh_size Mesh size for generation of new stratigraphy

Usage

Mesh_size

Real Value

Description

Defines the target element size near the fault when generating the mesh for the deposited sediment in which a fault is inserted. If the target mesh size is not specified, default values based on the mesh size of the existing sediment will be used.

Contact_sets List of contact sets associated with the fault

Usage

Contact_sets		IDM=ival
Character Names
where	ival	Number of geometry sets defining the contact set

Description

List of contact sets associated with the fault when it is created. If no Contact_sets are specified then a new contact set will be generated during the creation of the fault by fault insertion. This data only applies to faults that are not created or extended by fault insertion.

Extension_tolerance Extension tolerance for creating line tips (2D only)

Usage

Extension_tolerance

Real Value

Description

Extension tolerance for creating line tips (2D only, Default 0.5 (50%) of the adjacent facet length). If the tolerance is greater than zero the start and the end of the line will be extended if the tolerance would lead to intersection with a surface boundary rather than forming a line tip internal to a surface.

Root_tolerance Tolerance for intersection of root of new inserted faults (2D only)

Usage

Root_tolerance

Real Value

Description

Tolerance for intersection of root of new inserted faults (2D only, Default 0.2 (20%) of the adjacent facet length). May need to be increased if the fault is rooted on an older fault to ensure that the intersection is evaluated with sufficient tolerance.

Stablisation_load_fact Stabilisation surface stress factor to be applied to exposed fault surfaces

Usage

Stablisation_load_fact

Real Value

Description

Defines a multiplication factor for the surface load (defined via Applied_stress in Stratigraphy_surface_load) to be applied to an exposed fault (Default 1.0). Note that for a surface load to be applied to exposed fault surfaces Fault_load_flag 1 should be specified in Stratigraphy_surface_load and/or in Stratigraphy_basal_load.

Face_load_update_frequency Frequency for update of face loading information

Usage

Face_load_update_frequency

Integer Value

Description

Frequency for update of face loading information (Default 200 steps).

Face_load_ramp_frequency Number of steps for ramping up face load on a newly exposed fault node

Usage

Face_load_ramp_frequency

Integer Value

Description

Number of steps defined to ramp up the face load on a newly exposed fault node (Default 200 steps).

Footwall_surf_cont_flag Footwall-to-surface contact extension flag

Usage

Footwall_surf_cont_flag

Integer Value

Description

Flag to automatically add the model top surface to the fault footwall in 2-D for contact processing to allow the hangingwall of compressional faults to override the model surface if the fault offset is sufficiently large. Valid values are:

• 0 - Do not add model surface to fault contact definition

• 1 - Add model surface to fault contact definition

Dip_direction Dip direction in 2-D

Usage

Dip_direction

Character Name

Description

By default the dip direction is set using the line topology defining a fault. Shallow dip faults in a sloping sediment where part of a detachment is included in the fault definition can result in ambiguous conditions, as both the left and right side of the fault definition is elevated. In this case manual definition of the dip direction is required. Valid values are:

• "Left" - Left dipping fault

• "Right" - Right dipping fault

Seeding_variables List of seeding variables

Usage

Seeding_variables		IDM=ival
Character Names
where	ival	Number of seeding variables

Description

Defines the list of allowable seeding variables. These variables are dependent on the constitutive model type of the groups in which faults will be seeded. Seeding_variables allows the definition of a list of the variables that are going to be used. The valid variables are:

• "P_strnv" - Plastic volume strain for the SR3, SR4 and Cam Clay models. Then an initial value of volumetric plastic strain may be defined via Seeding_values

• "P_strn" - Plastic strain for the Drucker-Prager model. Then an initial value of effective plastic strain may be defined via Seeding_values

The initial strength will then be reduced and defined by the hardening curve.

Seeding_values Seeding values for fault

Usage

Seeding_values		IDM=ival
Real Values
where	ival	Number of seeding variables

Description

Defines the value of each seeding variable listed in Seeding_variables.

Factor_for_seeding_width Scale factor for fault seeding band width

Usage

Factor_for_seeding_width

Real Value

Description

Defines the scaling factor to control the fault seeding band width (Default is 1.0). This is the width over which elements will be identified as fault elements after seeding.