I was wondering what attributes, features or characteristics people commonly use in the field to differentiate between opening Mode I fractures/joints and shear fractures (Mode II or Mode III)?
I understand that Mode I fractures may develop plumose structures, whereas Mode II/III have shear displacement or may even develop slickenlines. However, for the practicality of detailed outcrop studies, where fracture surfaces are often not exposed and displacement on small bed-bound fractures may be very small, those features might not always be observable.
Are there any other features or characteristics that one could look for to differentiate between the different mode fractures in the field with some degree of certainty?
I'd appreciate any comments or suggestions.
Thanks,
Helge
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