@article{fdi:010080961,
  title = {{D}eep ductile shear zone facilitates near-orthogonal strike-slip faulting in a thin brittle lithosphere},
  author = {{L}iang, {C}. and {A}mpuero, {J}ean-{P}aul and {M}unoz, {D}. {P}.},
  editor = {},
  language = {{ENG}},
  abstract = {{S}ome active fault systems comprise near-orthogonal conjugate strike-slip faults, as highlighted by the 2019 {R}idgecrest and the 2012 {I}ndian {O}cean earthquake sequences. {I}n conventional {M}ohr-{C}oulomb failure theory, orthogonal faulting requires a zero frictional coefficient (pressure-insensitive), which is unlikely in the brittle lithosphere. {T}he simulations developed here show that near-orthogonal faults can form in the brittle layer by inheriting the geometry of orthogonal shear zones nucleated in the deep ductile (pressure-insensitive) layer. {I}n particular, if the brittle layer is sufficiently thinner than the ductile fault root, near-orthogonal faulting is preserved at the surface. {T}he preservation is further facilitated by a depth-dependent strength in the brittle layer. {C}onversely, faults nucleated within the brittle layer are unlikely to form at orthogonal angles. {O}ur model thus offers a possible explanation for orthogonal strike-slip faulting and reveals the significant interactions between the structure of faults in the brittle upper lithosphere and their deep ductile roots. {P}lain {L}anguage {S}ummary {S}ome notable earthquakes have occurred on sets of horizontally sliding vertical faults that cross each other at almost right angles (90 degrees). {T}his is puzzling because the conventional theory of how {E}arth's brittle outer shell, the crust, breaks predicts a narrower angle between faults, close to 60 degrees. {O}ur work offers an explanation to this puzzle. {T}heory also predicts that faults can form at right angles in rocks whose strength does not depend on the pressure acting on them. {T}his is precisely the case in the deep viscous rocks that lie below the crust. {O}ur computer simulations show that a pair of faults formed at right angle in deep viscous rocks can then grow upwards, gradually evolving to the narrower angle expected in the crust. {I}f the crust is too thin, the faults reach the surface with almost right angles. {O}ur proposed mechanism is effective on brittle crusts that are thinner than their viscous roots, which is the case in some regions where faulting at right angle is observed. {T}hus, our results show that the ductile root has important effects on the geometry of faults in the crust. {K}ey {P}oints . {S}imulations reveal shear bands in deep ductile layer induces orthogonal strike-slip faulting in thin brittle lithosphere {F}aults nucleated in brittle lithosphere are unlikely to form at orthogonal angles {L}ow confining pressure at shallow depth facilitates near-orthogonal strike-slip faulting},
  keywords = {3{D} numerical simulation ; brittle-ductile ; lithospheric structure ; orthogonal faults ; strike-slip},
  booktitle = {},
  journal = {{G}eophysical {R}esearch {L}etters},
  volume = {48},
  numero = {2},
  pages = {e2020{GL}090744 [9 ]},
  ISSN = {0094-8276},
  year = {2021},
  DOI = {10.1029/2020gl090744},
  URL = {https://www.documentation.ird.fr/hor/fdi:010080961},
}