Altyn Tagh fault (ATF) vs. San Andreas fault (SAF).

The ATF is a 1500km long, strike-slip fault that is slipping at high rates (~20 mm/yr). We can use techniques developed on the SAF and apply them to determine the stress oreintations near the ATF.

The Stats

The San Andreas

Is slipping at ~25-35 mm/yr.
Cuts relatively young ~30 km thick crust.
Is the most studied fault in the world.
Has many types of stress data.
Including focal mechanisms, bore hole breakouts, hydorfractures, fault-slip data, and fold oreintations.
Is poorly oriented.

The Altyn Tagh

Is slipping at ~20 mm/yr.
Cuts relatively old 60 km thick crust
Has had much less study.
Has less and lower quality stress data.
Including focal mechanisms, fault-slip data, and fold oreintations.
Orientation of Max stress is unknown.

The determination of stress orientations of the ATF is a peliminary study that is based on the above geologic and geophysical data. This study is very simplified and makes the following assumptions.

Assumptions

The maximum compressive stress is parallel to the P-axis of the focal mechanisms.
The inferred maximum stress is at 30 degress to fault slip directions.
The inferred max. stress is perpendicular to actively shortening anticlinal ridges.

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