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High-angle active conjugate faults in the Anza-Borrego shear zone, Southern California
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  • Xiaoyu Zou,
  • Yuri Fialko,
  • Andrew Dennehy,
  • Alexander Cloninger,
  • Shabnam Semnani
Xiaoyu Zou
Institute of Geophysics and Planetary Physics, Scripps Institute of Oceanography, UC San Diego

Corresponding Author:[email protected]

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Yuri Fialko
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Andrew Dennehy
Committe on Computational and Applied Mathematics, University of Chicago
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Alexander Cloninger
Department of Mathematics & Halicioglu Data Science Institute, UC San Diego
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Shabnam Semnani
Department of Structural Engineering, UC San Diego
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Orientations of active antithetic faults can provide useful constraints on in situ strength of the seismogenic crust. We use LINSCAN, a new unsupervised learning algorithm for identifying quasi-linear clusters of earthquakes, to map small-scale strike-slip faults in the Anza-Borrego shear zone, Southern California. We identify 332 right- and left-lateral faults having lengths between 0.1-3 km. The dihedral angles between all possible pairs of conjugate faults are nearly normally distributed around 70 degrees, with a standard deviation of 30 degrees. The observed dihedral angles are larger than those expected assuming optimal fault orientations and the coefficient of friction of 0.6-0.8, but similar to the distribution previously reported for the Ridgecrest area in the Eastern California Shear Zone. We show that the observed fault orientations can be explained by fault rotation away from the principal shortening axis due to a cumulated tectonic strain. 
26 Oct 2023Submitted to ESS Open Archive
27 Oct 2023Published in ESS Open Archive