Recent Discoveries About the Orientation of Maximum Compressive Stress to Fault Planes.

The San Andreas fault (SAF) is the best natural laboratory to study the stresses that drive faulting. Zoback et al., 1987 used geophysical and geologic data to determine if the San Andreas fault is well orineted for slip. In other words, is Sigma one 30 degrees to the fault?

Geologic data shows fold axis near perpendicular to the fault.

3

Earthquake focal mechanisms also show maximum compressive stress orthoganol to the fualt.

2


Compilation of stress data show that maximum compressive stress is oriented ~75 degrees to the SAF

d

The San Andreas fault is not well oriented.


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