Morphology, structure and evolution of California Continental Borderland restraining bends

Abstract

Exceptional examples of restraining and releasing bend structures along major strikeslip fault zones are found in the California continental Borderland. Erosion in the deep sea is diminished, thereby preserving the morphology of active oblique fault deformation. Long-lived deposition of turbidites and other marine sediments preserve a high-resolution geological record of fault zone deformation and regional tectonic evolution. Two large restraining bends with varied structural styles are compared to derive a typical morphology of Borderland restraining bends. A 60-km-long, 158 left bend in the dextral San Clemente Fault creates two primary deformation zones. The southeastern uplift involves 'soft' turbidite sediments and is expressed as a broad asymmetrical ridge with right-stepping en echelon anticlines and local pull-apart basins at minor releasing stepovers along the fault. The northwest uplift involves more rigid sedimentary and possibly igneous or metamorphic basement rocks creating a steep-sided, narrow and more symmetrical pop-up. The restraining bend terminates in a releasing stepover basin at the NW end, but curves gently into a transtensional releasing bend to the SE. Seismic stratigraphy indicates that the uplift and transpression along this bend occurred within Quaternary times. The 80-kmlong, 30-408 left

Complex multifault rupture during the 2016 M w 7.8 Kaikōura earthquake, New Zealand

“…This demonstrates that dislocation models struggle to reproduce the transfer of coseismic slip through complex fault networks or the asymmetric uplift and subsidence patterns around faults. The fault configuration around the uplifted block, asymmetric uplift pattern (40) and larger scale MFS is consistent with this structure being part of a pop-up structure within a restraining bend between the Jordan Thrust and Kekerengu Faults. Furthermore, a semi-continuous GPS installed within the Papatea block within two days of the earthquake shows negligible vertical post-seismic displacements and there have been no aftershocks associated with the lineament (Figure 4).…”

Structural analysis of S-wave seismics around an urban sinkhole: evidence of enhanced dissolution in a strike-slip fault zone

“…The normal faults seen in S1 were also identified in S4, while two almost bowl-shaped structures (red dashed circles) are visible in the south-west and the north-east. maximum horizontal stress (Tikoff and Teyssier, 1994;Legg et al, 2007). Alternatively, if there are jogs along the strike of a strike-slip fault, this will produce constraining and releasing bends (Cunningham and Mann, 2007), which will cause, after movement, reverse and normal faults, respectively, with strikes similar to the strike-slip fault, along the strike of the strike-slip fault (Crowell, 1974;Christie-Blick and Biddle, 1985;Gamond, 1987, Fig.…”

“…1). Most probably this movement took place during the Upper Cretaceous/early Tertiary inversion phase in Europe (Tanner et al, 1998;Littke et al, 2008;Kley and Voigt, 2008;Tanner and Krawczyk, 2017). The south-eastern part of the HFZ cross-cuts the town of Schmalkalden.…”

Strike-slip geometry inferred from the seismicity of the Northern-Central Apennines (Italy)

“…13) while the restraining bends lead to pop-up structures (their long axes being parallel to the direction of extension, Fig. 13) (Cunningham and Mann, 2007;Legg et al, 2007). Martini et al, 2001;Piccardi et al, 1999) and focal mechanisms, modified after Bagh et al (2007); (b) modified Riedel shear system, aligned parallel to the orientation of the Apennine Chain, including a model explaining the occurrence of restraining and releasing bends along a snake fault (Davis and Reynolds, 1996).…”