Faulting

3.3 Faulting Event

In order to define a faulting event place a Fault icon in the History window. You will then be provided with the Fault definition window.

Fault Definition Window

Fault surfaces can be planar or curved but the slip vector is always parallel across the plane.

The X,Y,Z coordinates define one point on the fault (and the centre of symmetry of ring, elliptical and curved faults), and most of the other parameters are normal structural definitions.

Translational events implicitly generate fault slip vector lineations.

For DXF triangulated surface faults, the fault plane if infinite in extent, and except where the DXF surface is defined, flat planar, and the slip vector is uniform in length parallel to the fault plane. The X,Y,Z coordinates in this case define the position of the top right corner of the surface, looking down on the plane.

GROUP	NAME	FUNCTION
Form	Geometry:
	Translation	Simple planar translational faults
	Rotation	Simple planar rotational faults
	Elliptical	Elliptical fault Elliptical fault plane, these faults displace material within an ellipsoidal zone defined by the long axes of the ellipsoid, with slip vectors dying off away from the centre of the ellipsoid.
	Curved	Curved fault Curved fault plane, essentially an elliptical fault with a curved fault surface, which is defined by its profile, and the amount of decay of the curvature away from the plane of definition.
	Ring	Ring faultRing fault, producing a cylindrical volume of slipped material. Dip and Dip Direction are actually the to Plunge and Plunge Direction of central axis of ring fault.
	Movement:
	Hanging Wall	Hanging wall Hanging wall only movement on fault (hanging wall is inside of ring fault).
	Foot Wall	Foot wall Foot wall only movement on fault (foot wall is outside of ring fault).
	Both	Both footwall and hanging Both footwall and hanging wall. The total slip vector is divided into 50% movement in each direction.
	AlterationsAlterations:
	None	No alteration halo associated with this event
	Top	Alteration halo on hanging wall side of fault
	Bottom	Alteration halo on foot wall side of fault
	Both	Alteration halo on both sides of fault
	Edit	Brings up Alteration Profile window
	Define Colour	Defines colour of fault plane for vector graphics displays
	Show Profile	Shows Profile Definition window for Curved Faults
Surface Shape	Flat Plane	Fault plane defined only by Geometries options (see above)
	DXF SurfaceDXF Surface	Part of fault plane defined by DXF triangulated surface
	ViewView	View grey scale image of DXF surface topography
	X Dim	Scaling factor for X direction of plane
	Y Dim	Scaling factor for Y direction of plane
	Z Dim	Scaling factor for Z direction of plane

Position	X	X position of one point on fault plane (centroid of elliptical and curved faults, centre of rotation of rotational faults, top right hand corner of DXF surface bounding rectangle)
	Y	Y position of one point on fault plane
	Z	Z position of one point on fault plane
Orientation	Dip Dir	Dip Direction of Fault Plane
	Dip	Dip of Fault Plane
	Pitch	Pitch of slip vector on fault plane
	Trace From ImageTrace From Image	Allows orientation of fault to be traced directly from BMP format file.
Scale	Rotation	Rotation of fault block in degrees, around normal to fault passing through X,Y,Z, anticlockwise looking down rotation axis
	Slip	Displacement on fault parallel to slip vector
	Amplitude	Amplitude of curvature of fault, as defined on profile
	Radius	Radius of Ring Fault
	Cyl Index	Cylindricity index for decay of curvature of curved faults. Distance perpendicular to profile at which amplitude drops to 1/2 following a exponential drop-off
	Profile Pitch	Orientation of Curved Fault Profile (Independant of Slip Vector Pitch)
Scale (Ellipsoid)	X Axis	Long axes of ellipsoid for elliptical faults (X=slip direction, XZ plane = fault) The magnitude of the chosen slip vector must always be less than 45% of the X value.
	Y Axis	Magnitude of ellipsoid normal to fault plane
	Z Axis	Magnitude of ellipsoid normal to slip vector

Tracing Fault Orientations Directly From Maps

When the Trace From Image button is selected, the program will ask for a .BMP format image from which fault trends can be traced directly. The scaling is determined by the Fault Trace Control Window, which determines the coordinates of the NW and SE corners. The two points on the fault trace may be defined by clicking in the Image window, and may be edited by dragging them.