Inclusion on East Side of Fault, with Buried Inclusion on West Side of Fault

Rigid inclusion are located on both sides of the fault. On the east side, it extends from the surface to a depth of 25 km. On the west side, it extends from a depth of 12.5 km to a depth of 25 km. On both sides, the inclusion measures 25 km in the north-south direction, and 12.5 km in the west-east direction.

Two different methods are used to create shear stress:

1. Apply a right-lateral shear distortion to the side and bottom boundaries of the model. No fault slip is allowed. This method is used for figures 1 to 5 below.
    
2. Create a screw dislocation at a depth of either 12.5 km or 25 km, by locking the upper part of the fault and permitting the lower part of the fault to slip freely. A right-lateral displacement is applied to the side and bottom boundaries of the model, as if the two sides of the model were rigid blocks sliding past each other. No shear distortion is applied. This method is used for figures 6 and 7 below.

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Fig. 1. Inclusion viewed from the east. The inclusion is shown in gray, viewed from the east side of the fault surface. FEM cells are 625 meters on a side. Fault surface is colored by normal stress.

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Fig. 2. Inclusion viewed from the west. The inclusion is shown in gray, viewed from the west side of the fault surface. FEM cells are 625 meters on a side. Fault surface is colored by normal stress.

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Fig. 3. Normal stress on the fault surface, generated by a shear distortion. Fault surface viewed from the east, colored according to normal stress. Red denotes tension, and blue denotes compression.

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Fig. 4. Warping of fault surface, generated by a shear distortion. Fault surface viewed from the east, colored according to west-east displacement. Red denotes displacement eastward (toward the viewer), and blue denotes displacement westward (away from the viewer).

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Fig. 5. Shear stress on the fault surface, generated by a shear distortion. Fault surface viewed from the east, colored according to shear stress. Red denotes maximum shear stress, and blue denotes minimum shear stress.

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Fig. 6. Normal stress on the fault surface, generated by a screw dislocation at 12.5 km depth. Fault surface viewed from the east, colored according to normal stress. Red denotes tension, and blue denotes compression.

The screw dislocation here runs just above the buried inclusion on the west side of the fault.

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Fig. 7. Normal stress on the fault surface, generated by a screw dislocation at 25 km depth. Fault surface viewed from the east, colored according to normal stress. Red denotes tension, and blue denotes compression.

The screw dislocation here runs just underneath the inclusion. Note that the pattern of stress is similar to that produced by a shear distortion.