Fault Networks in Triaxial Tectonic Settings: Analog Modeling of Distributed Continental Extension With Lateral Shortening

• Published in: Tectonics (Washington, D.C.) D.C.), 2024-05, Vol.43 (5), p.n/a
• Main Authors: Liu, Jun, Rosenau, Matthias, Brune, Sascha, Kosari, Ehsan, Rudolf, Michael, Oncken, Onno
• Format: Article
• Language: English
• Subjects: analog modeling; Boundary conditions; Crustal thickness; Deformation; distributed deformation; Fault lines; fault networks; Graben; Localization; principal horizontal strain ratio; Rheology; Scale models; Strain; Systematics; Tectonics; triaxial tectonics; Upper mantle; Viscosity
• ISSN: 0278-7407; 1944-9194
• DOI: 10.1029/2023TC008127

Triaxial deformation is a general feature of continental tectonics, but its controls and the systematics of associated fault networks remain poorly understood. We present triaxial analog experiments mimicking crustal thinning resulting from distributed longitudinal extension and lateral shortening. Contemporary longitudinal extension and lateral shortening are related by the principal horizontal strain ratio (PHSR). We investigate the effect of crustal geometry, rheology and strain rate on deformation localization, faulting regime and pattern, and PHSR in brittle and brittle‐viscous crustal‐scale models. We find that in brittle models the fault networks reflect the basal boundary condition and fault‐density scales inversely with brittle layer thickness. In brittle‐viscous models, as strain rate (ė) decreases, (a) Three fault patterns emerge: conjugate sets of strike‐slip faults (ė > 3 × 10−4 s−1, PHSR > 0.31), sets of parallel oblique normal faults (ė = 0.3–3 × 10−4 s−1, PHSR = 0.15–0.25), horst‐and‐graben system (ė