Analog models of restraining stepovers in strike-slip fault systems

McClay, Ken; Bonora, Massimo

doi:10.1306/8626c7ad-173b-11d7-8645000102c1865d

Cited by 67 publications

(24 citation statements)

References 31 publications

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“…Such local stress changes also occur at stepovers in strike-slip fault systems (Okubo and Schultz, 2006;De Paola et al, 2007). The TZs in our models do resemble releasing bends observed in such settings, yet the kinematics do not fit since releasing bends form in a dextral slip environment (for a right-stepping fault segment arrangement, McClay and Bonora, 2001), whereas our models involve sinistral slip.…”

Section: Rift Segment Linkage Under Sinistral Oblique Extension Condimentioning

confidence: 76%

How oblique extension and structural inheritance influence rift segment interaction: Insights from 4D analog models

Zwaan

Schreurs

2017

Interpretation

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Rifting of the continental lithosphere involves the initial formation of distinct rift segments, often along preexisting crustal heterogeneities resulting from preceding tectonic phases. Progressive extension, either orthogonal or oblique, causes these rift segments to interact and connect, ultimately leading to a full-scale rift system. We study continental rift interaction processes with the use of analog models to test the influence of a range of structural inheritance (seed) geometries and various degrees of oblique extension. The inherited geometry involves main seeds, offset in a right-stepping fashion, along which rift segments form as well as the presence or absence of secondary seeds connecting the main seeds. X-ray computer tomography techniques are used to analyze the 3D models through time, and results are compared with natural examples. Our experiments indicate that the extension direction exerts a key influence on rift segment interaction. Rift segments are more likely to connect through discrete fault structures under dextral oblique extension conditions because they generally propagate toward each other. In contrast, sinistral oblique extension commonly does not result in hard linkage because rift segment tend to grow apart. These findings also hold when the system is mirrored: left-stepping rift segments under sinistral and dextral oblique extension conditions, respectively. However, under specific conditions, when the right-stepping rift segments are laterally far apart, sinistral oblique extension can produce hard linkage in the shape of a strike-slip-dominated transfer zone. A secondary structural inheritance between rift segments might influence rift linkage, but only when the extension direction is favorable for activation. Otherwise, propagating rifts will simply align perpendicularly to the extension direction. When secondary structural grains do reactivate, the resulting transfer zone and the strike of internal faults follow their general orientation. However, these structures can be slightly oblique due to the influence of the extension direction. Several of the characteristic structures observed in our models are also present in natural rift settings such as the Rhine-Bresse Transfer Zone, the Rio Grande Rift, and the East African Rift System.

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Section: Rift Segment Linkage Under Sinistral Oblique Extension Condimentioning

confidence: 76%

How oblique extension and structural inheritance influence rift segment interaction: Insights from 4D analog models

Zwaan

Schreurs

2017

Interpretation

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“…These modeled stresses are almost perpendicular to that of the segment between the fault tips (red dashed line in Figure 9) and cause local compression toward it. This compression has also been evidenced by sediment thickening close to the restraining bend in a sand-box model (McClay and Bonora, 2001). Overall, the shallow sediments near these reliefs are most likely to be compressed as the tectonic activity continued and the resultant increasing pore pressure primed the formation of the gas emissions ( Figure 10).…”

Section: Gas Emission In Transtensile Regimementioning

confidence: 81%

Gas Emissions in a Transtensile Regime Along the Western Slope of the Mid-Okinawa Trough

Cai

et al. 2021

Front. Earth Sci.

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Gas emissions from the seabed are favored by tectonically active settings and their distribution is often linked to the nearby faults. Here we use the multi-beam echo-sounder (MBES) and the multi-channel seismic (MCS) data and a sediment core to show multiple gas emissions near the fault complex out of the shelf of the Mid-Okinawa Trough. The features indicating the gas emissions include 1) a set of the conical positive reliefs at the seabed, 2) the bundle-shaped clusters of the high-backscattering intensities in the water column, and 3) the sub-circular medium-to high-backscattering patches at the level of the seabed. These features together show that the free gases can escape from the marine sediments then rise in the water column at present, while some other gases trapped in the sub-seafloor sediment might contribute to the precipitation of the authigenic carbonates in the past. The spatial relationship between the gas emissions and the faults suggests that the faulting driven by the back-arc extension should provide the permeable migration pathways for the gas emissions to operate, and thus determines where most of them could potentially occur. The area surrounding the restraining bend concentrates part of the gas emissions rather than along the fault lines, due to the lateral compression and the structural complexity. This is demonstrated by the results of the numerical model of finite element method (FEM), which shows two gas emissions are within the compressed zone of the modeled restraining step-over. This study provides new evidence of the role of the tectonic stresses in determining the sites of degassing of marine sediments.

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“…Like many other strike-slip faults around the world, the coseismic surface rupture of the Milun Fault did not generate a simple, co-planar fault trace (Segall and Pollard 1980;Aviles et al 1987;Scholz 1990;Sylvester 1988;McClay and Bonora 2001;Klinger 2010). The surface deformation mostly occurred as arrays of en-echelon arranged Riedel shears (mainly R), tension fissures and buckled moletracks synthetic to the direction of PDZ (Tchalenko 1970;Davis et al 2000;Chemenda et al 2016).…”

Section: Surface Ruptures Of the Milun Faultmentioning

confidence: 87%

Investigating the Milun Fault: The coseismic surface rupture zone of the 2018/02/06 ML 6.2 Hualien earthquake, Taiwan

Huang¹,

Yen²,

Wu³

et al. 2019

Terr. Atmos. Ocean. Sci.

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On 6 February 2018, a M L 6.2 earthquake struck the east coast of Taiwan and caused more than 200 casualties in the Hualien area. The mainshock initiated at a shallow depth of 6.3 km and was accompanied by numbers of foreshocks and aftershocks. Coseismic ruptures widely occurred along the Milun Fault with various deformational structures and caused a variety of damage. Extensive field survey and drone-based images reveal the distribution of offsets and the characteristics of the surface ruptures. The major surface ruptures were mostly synthetic and antithetic Riedel shears interlinked by push-up moletracks or tensional fissures. The strike of the principal displacement zone evolved from northeast to northwest and defined a 7.5-km-long NS fault trace concave to the east. The vertical offset reached its maximum of 50 cm on the north segment and became insignificant toward south. Both on-fault single measurements and cumulative sinistral offsets estimated across the rupture zones showed the pattern of southward declining with the maximum offset of 77 cm in the north. The width of the damage zone increased from 1 -20 m to maximum 270 m in the south where the overstepping segments occurred. The development of step-overs is significant in the south, especially in the downtown area where slip is distributed across a transpressional area. Overall, the distinct features of the coseismic ruptures reflect the complex near-surface geology along the Milun Fault and offer new insights for future hazard assessments of the Hualien area.

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Analog models of restraining stepovers in strike-slip fault systems

Cited by 67 publications

References 31 publications

How oblique extension and structural inheritance influence rift segment interaction: Insights from 4D analog models

How oblique extension and structural inheritance influence rift segment interaction: Insights from 4D analog models

Gas Emissions in a Transtensile Regime Along the Western Slope of the Mid-Okinawa Trough

Investigating the Milun Fault: The coseismic surface rupture zone of the 2018/02/06 ML 6.2 Hualien earthquake, Taiwan

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