Strain partitioning in highly oblique rift settings: Inferences from the southwestern margin of the Gulf of California (Baja California Sur, México)

Bonini, Marco; Cerca, Mariano; Moratti, Giovanna; López‐Martínez, Margarita; Corti, Giacomo; Gracia‐Marroquín, Diego

doi:10.1029/2019tc005566

Cited by 14 publications

(27 citation statements)

References 109 publications

(249 reference statements)

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“…-The strike-slip faults responsible for transform margins formation do not form parallel to the plate motion except for highly oblique extension (α > 30°) -En-échelon deformation and offset basins are required to develop strike-slip linkage shear zones evolving to transform margin -Localized strike-slip shear zones form after normal faults once the lithosphere is already thermally and mechanically weakened. -The lithosphere weakening leads to stress and strain re-orientation under same kinematic boundary conditions Figure 1: a) Simplified structural map of the Gulf of California rift system (modified from Bonini et al, 2019;Ferrari et al, 2018;Fletcher et al, 2007). Large white arrows display the plate motion between the North American plate and the Pacific plate from Plattner et al, (2007).…”

Section: Resultsmentioning

confidence: 99%

“…The structural analysis performed on faults and shear zones shows that the average angle between the rift system and the extension direction is ~20° (e.g. Bonini et al, 2019). Moreover, the general trend of normal faults strike in the continental margin shows a NNW orientation while the strike-slip faults display a NW-SE strike, indicating a ~20˚ difference in orientation.…”

Section: High Obliquity Rift Systemsmentioning

confidence: 99%

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Looking beyond kinematics: 3D thermo-mechanical modelling reveals the dynamic of transform margins

Jourdon¹,

Kergaravat²,

Duclaux³

et al. 2021

Preprint

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Abstract. Transform margins represent ~30 % of the non-convergent margins worldwide. Their formation and evolution have long been addressed through kinematic models that do not account for the mechanical behaviour of the lithosphere. In this study, we use high resolution 3D numerical thermo-mechanical modelling to simulate and investigate the evolution of the intra-continental strain localization under oblique extension. The obliquity is set through velocity boundary conditions that range from 15° (high obliquity) to 75° (low obliquity) every 15° for strong and weak lower continental crust rheologies. Numerical models show that the formation of localized strike-slip shear zones leading to transform continental margins always follows a thinning phase during which the lithosphere is thermally and mechanically weakened. For low (75°) to intermediate (45°) obliquity cases, the strike-slip faults are not parallel to the extension direction but form an angle of 20° to 40° with the plates' motion while for higher obliquities (30° to 15°) the strike-slip faults develop parallel to the extension direction. Numerical models also show that during the thinning of the lithosphere, the stress and strain re-orient while boundary conditions are kept constant. This evolution, due to the weakening of the lithosphere, leads to a strain localization process in three major phases: (1) strain initiates in a rigid plate where structures are sub-perpendicular to the extension direction; (2) distributed deformation with local stress field variations and formation of transtensional and strike-slip structures; (3) formation of highly localized plates boundaries stopping the intra-continental deformation. Our results call for a thorough re-evaluation of the kinematic approach to studying transform margins.

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Section: Resultsmentioning

confidence: 99%

Section: High Obliquity Rift Systemsmentioning

confidence: 99%

Looking beyond kinematics: 3D thermo-mechanical modelling reveals the dynamic of transform margins

Jourdon¹,

Kergaravat²,

Duclaux³

et al. 2021

Preprint

View full text Add to dashboard Cite

show abstract

“…Woodlark basin; Taylor et al, 2009). This conceptual model and its offspring based on rigid plate tectonics do not reflect the whole intra-continental deformation phase associated with progressive strain localization and structure re-orientation (Ammann et al, 2017;Brune, 2014;Brune and Autin, 2013;Mondy et al, 2018;Le Pourhiet et al, 2017). This has first-order implications for tectonic plate reconstructions and the interpretation of a margin's progressive deformation history.…”

Section: Introductionmentioning

confidence: 94%

“…Except in experiments approaching pure strike-slip conditions, models show that the onset of intra-continental deformation localizes on structures at half the angle of obliquity (i.e. the angle between the extension-perpendicular direction and rift trend) (Brune, 2014;Duclaux et al, 2020;Withjack and Jamison, 1986). Then, depending on the obliquity (defined as the angle between the plate motion direction and the average rift trend) the deformation evolution differs.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Looking beyond kinematics: 3D thermo-mechanical modelling reveals the dynamics of transform margins

et al. 2021

View full text Add to dashboard Cite

Abstract. Transform margins represent ∼ 30 % of non-convergent margins worldwide. Their formation and evolution have traditionally been addressed through kinematic models that do not account for the mechanical behaviour of the lithosphere. In this study, we use high-resolution 3D numerical thermo-mechanical modelling to simulate and investigate the evolution of intra-continental strain localization under oblique extension. The obliquity is set through velocity boundary conditions that range from 15∘ (high obliquity) to 75∘ (low obliquity) every 15∘ for rheologies of strong and weak lower continental crust. Numerical models show that the formation of localized strike-slip shear zones leading to transform continental margins always follows a thinning phase during which the lithosphere is thermally and mechanically weakened. For low- (75∘) to intermediate-obliquity (45∘) cases, the strike-slip faults are not parallel to the extension direction but form an angle of 20∘ to 40∘ with the plate motion vector, while for higher obliquities (30∘ to 15∘) the strike-slip faults develop parallel to the extension direction. Numerical models also show that during the thinning of the lithosphere, the stress and strain re-orient while boundary conditions are kept constant. This evolution, due to the weakening of the lithosphere, leads to a strain localization process in three major phases: (1) initiation of strain in a rigid plate where structures are sub-perpendicular to the extension direction; (2) distributed deformation with local stress field variations and formation of transtensional and strike-slip structures; (3) formation of highly localized plate boundaries stopping the intra-continental deformation. Our results call for a thorough re-evaluation of the kinematic approach to studying transform margins.

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Inference of fracturing zones and degrees of fluid content in the Las Tres Virgenes volcanic complex based on an analysis of seismic anisotropy

Chacón-Hernández,

Campos-Enríquez,

Zúñiga

et al. 2024

Acta Geophys.

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Anisotropy strength in the Tres Vírgenes Volcanic Complex, Baja California Sur, Mexico, is analyzed employing 558 seismic events collected from 2009 to 2013. It was possible to delineate zones and volumes with the highest fracture densities, which are mainly located between the El Viejo and El Azufre volcanoes and around the La Reforma–El Azufre fault system, near some other mapped faults in the area (e.g., El Azufre, El Partido, El Volcán, El Viejo 1, and El Viejo 2 faults); likewise toward the La Virgen volcano and around the La Virgen-El Campamento and El Volcán faults. Individual delay times reached values of up to 0.16 s and an anisotropy percentage of up to 10.3%, with a pervasive anisotropy observed from at least a hypocentral distance of 3.5 km. High fracturing levels are observed from a depth of 7.0 km. Differences between splitting delays and the dominant frequency peaks obtained from the fast S phases allowed considering fracture systems with different degrees of fluid contents. Fractures with minor fluid contents were assumed for delay times higher than 0.03 s with lower dominant frequency peaks (< 1.0 Hz). Higher concentrations of fluid inclusions were assumed for splitting delays higher than 0.03 s but with larger dominant frequency peaks (> 1.0 Hz). Fractures systems chemically sealed or impermeable sealing caps were assumed for low splitting delays (< 0.02 s) with low dominant frequencies (< 1.0 Hz). These different fracture systems seem to be observed at least from 5- to 6-km depth intervals. Likewise, an analysis of the fast polarization directions with respect to different depth ranges (spanning from 3.0 to 8.0 km) has allowed observations of a strong NW–SE regional fracture system accompanied by minor NE–SW fracture systems. However, noteworthy variations from NW–SE to NE–SW, N–S, and E–W in fast polarization directions in rose diagrams have been preferentially observed for those seismic events deeper than 4–5 and 5–6 km in some areas, which could be indicating the location of magmatic bodies that probably caused the reorientation on fracture systems by changes in the local stress field. These magmatic bodies might be supported by a decrease in the dominant frequency peaks (lower than 1.0 Hz), percentage of anisotropy (from 0.1 to 2.5%), and S-wave velocities (from 1.0 to 2.7 km/s), which seem to be located from the 4.0-km depth but more concentrated from the 5–6-km depth interval.

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Strain partitioning in highly oblique rift settings: Inferences from the southwestern margin of the Gulf of California (Baja California Sur, México)

Cited by 14 publications

References 109 publications

Looking beyond kinematics: 3D thermo-mechanical modelling reveals the dynamic of transform margins

Looking beyond kinematics: 3D thermo-mechanical modelling reveals the dynamic of transform margins

Looking beyond kinematics: 3D thermo-mechanical modelling reveals the dynamics of transform margins

Inference of fracturing zones and degrees of fluid content in the Las Tres Virgenes volcanic complex based on an analysis of seismic anisotropy

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