Three-dimensional fault geometries and interactions within experimental models of multiphase extension

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We use experimental (analog) models to examine the threedimensional (3-D) fault geometries and interactions that develop during two phases of noncoaxial extension. In the models, a homogeneous layer of wet clay undergoes two phases of extension whose directions differ by 45°. The resulting fault pattern varies significantly with depth. At shallow levels, second-phase normal faults accommodate most second-phase extension. At depth, both second-phase normal faults and reactivated, first-phase faults with oblique slip accommodate most second-phase extension. A variety of interactions occurs between first-phase and second-phase faults. One interaction involves the upward propagation of second-phase faults from tips of reactivated, blind, first-phase faults. These hybrid faults have deep segments that strike subperpendicular to the first-phase extension direction and shallow segments whose strike varies with depth, becoming increasingly subperpendicular to the second-phase extension direction at shallow levels. A second interaction involves the nucleation of second-phase normal faults on the surfaces of reactivated, first-phase faults. These splay faults propagate upward and laterally from their nucleation sites into the hanging walls of the first-phase faults. As they propagate, they commonly encounter and link with different first-phase faults. The resulting composite faults have zigzag geometries in both map and cross-sectional views. A third interaction involves either the termination of second-phase antithetic normal faults against or near first-phase faults or the offset of first-phase faults by second-phase antithetic normal faults. The 3-D fault patterns and interactions within ourmodels closely resemble those within the Taranaki basin of offshore New Zealand andMilne Point on Alaska's North Slope.

Original languageEnglish (US)
Pages (from-to)1767-1789
Number of pages23
JournalAAPG Bulletin
Issue number11
StatePublished - Nov 2017

All Science Journal Classification (ASJC) codes

  • Fuel Technology
  • Energy Engineering and Power Technology
  • Geology
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)


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