Abstract
Tectonic strain includes contributions from small faults, with length less than the thickness of the brittle upper crust. This study derives algebra to determine the strain associated with small faults that follow a power-law (i.e. fractal) distribution, independent of assumptions concerning how they relate to large faults in the same region, and discusses how to apply this algebra for a range of small fault sample types. The method is illustrated using as case studies the Jurassic extension in the North Sea, the Miocene and younger extension in the Gulf of Suez, and the Hercynian strike-slip faulting the Badajoz-Cordoba fault zone in southern Spain. My preferred estimates for the strain accommodated on small normal faults, with length <10 km, are ∼0.04 in the North Sea and ∼0.1 in the Gulf of Suez: ∼20 and ∼30% of the overall extensional strain in each region. This estimate makes the percentage of strain accommodated on small faults in the North Sea smaller than values in studies that assume that a single power law fits both small and large faults. My preferred estimate for the strain accommodated on small strike-slip faults in the Badajoz-Cordoba fault zone is ∼0.3, which may be ∼75% of the overall strain accommodated in this zone. These faults are more closely packed than the normal faults in the other localities.
Published Version
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