Non-steady-state slip rates emerge along evolving restraining bends under constant loading

Elston, Hanna; Cooke, Michele L.; Hatem, Alex

doi:10.1130/g49745.1

Cited by 6 publications

(8 citation statements)

References 28 publications

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“…Because the activity among fault strands in the San Gorgonio Pass has shifted over the past 100 ka, strands that were active 60 ka may have different activity now. Laboratory experiments of restraining bends with similar geometry to the San Andreas fault through the San Gorgonio Pass show that such bends are not stable fault configurations (Cooke, Schottenfeld, & Buchanan, 2013;Hatem et al, 2015) and slip rates can vary on time spans of ~50 ka (Elston, Cooke, & Hatem, 2022). For this reason, we only use slip rates from offset of features younger than ~16 ka to constrain the models.…”

Section: Impact Of Slip Rates and Their Uncertaintymentioning

confidence: 99%

Mechanical Analysis of Fault Slip Rate Sites within the San Gorgonio Pass Region, Southern California USA

Hatch¹,

Cooke²,

Elston³

2023

Preprint

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Crustal deformation models show incompatibility between inferred fault geometry and geologic slip rates where model and geologic slip rates disagree. We do not know if the impact of these incompatibilities is limited to near sites or have wider effect on the fault system deformation. Here, we investigate the roles of structural position of sites and uncertainty of slip rates using one suite of mechanical models that limits the dextral slip rates to within the range of observed slip rates at the sites of geologic investigations and another suite that explores the impact of each slip rate site on each other and on the nearby fault system. The suites of models employ two viable configurations for the southern San Andreas fault: with and without an active northern slip pathway around the San Gorgonio Pass. While the Active Northern Pathway model has greater mismatch to geologic slip rates < 16ka, it produces lesser off-fault deformation than the Inactive Northern Pathway model. The impact of strike-slip rate sites on the system depends on their structural positions. Sites along segmented faults may have lesser impact than either sites along the same fault segment or sites at fault branches. Consequently, inaccuracies in the slip rates used for seismic hazard assessment may have differing impacts depending on location of the slip rates. Fault branches along strike-slip faults warrant detailed investigation because these areas have high spatial variability of slip rate and accrue nearby off-fault deformation, affecting our ability to accurately assess seismic hazard of the region.

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Section: Impact Of Slip Rates and Their Uncertaintymentioning

confidence: 99%

Mechanical Analysis of Fault Slip Rate Sites within the San Gorgonio Pass Region, Southern California USA

Hatch¹,

Cooke²,

Elston³

2023

Preprint

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“…2). Faults in the analogue model 50 representing Mount Lebanon thrust show very smooth linkage (e.g. Roum fault) to central through-going fault and distributed linkage on the other side (e.g.…”

Section: Mount Lebanonmentioning

confidence: 99%

“…Lebanon has identical surface expression as experiments from physical models 51,56 . A recent model 50 shows a detailed evolution of the fault system in restraining bend, including curved thrust (e.g. Mount Lebanon thrust) nucleating with a single fault trace (e.g.…”

Section: Synthesis and Outlookmentioning

confidence: 99%

A validated geomechanical model for the strike-slip restraining bend in Lebanon

Fedorik

Maesano

Afifi

2022

Sci Rep

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Most of the methodologies used to validate complex strike-slip structures mainly rely on comparison with other well-known geological features or analogue laboratory models. This study adopts an approach based on the boundary element method at the regional scale to test the structural interpretation of a complex transpressional mountain range. Lebanon restraining bend represents the most prominent topographic transpressional feature along the Dead Sea Transform (DST). It consists of two mountain ranges: the Mount Lebanon and the Anti-Lebanon ranges. We built a 3D geometrical model of the fault surfaces based on previously studied natural examples, structural maps, satellite images, DEM interpretation and experimental analogue models of restraining bend or transpressional structures. Using a boundary element method, we modelled fault deformation response to the regional stress field. The simulation accurately predicts the shape and magnitude of positive and negative topographic changes and fault slip directions throughout the study area. We propose an original approach, which uses implementation of well-known fault geometries, surface and subsurface data, for structural validation in the complex strike-slip domain. Our results, validated by structural evidences, highlight that various structural styles lead to formation of Mt. Lebanon, Anti-Lebanon and Palmyrides structures. Furthermore, this simulation supports the hypothesis that the restraining bend of the DST formed in the widespread crustal weakness zone developed in the Late Jurassic to Early Createceous. We also propose recent Neogene tectonic evolution of the region based on our modelling and integrated with published U/Pb dating of fault zones and tectonostratigraphic evidence.

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“…In the face of these large uncertainties, collecting slip rate data from additional sites provides one way to improve constraints on active slip partitioning. However, in regions of multiple active faults with complex evolving geometry, where slip rates can vary both in space and in time (e.g., Elston et al, 2022;McGill et al, 2021;Zinke et al, 2017), this approach can yield slip rates that are inconsistent with each other. One such region is where the southern San Andreas fault in southern California forms a restraining bend in the San Gorgonio Pass region (SGPr) (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

“…These slip rates are averaged over different time periods (Table 1), which complicates their direct application to current seismic hazard assessment. Long term slip rates from very young deposits (fewer than five earthquakes) may be impacted by earthquake cycles (e.g., Styron, 2019) and older deposits have in- creasing vulnerability for recording temporal variation in slip rates (e.g., Rittase et al, 2014;Hatem et al, 2020;Elston et al, 2022;Zinke et al, 2017). An interesting outcome of having abundant slip rate data is that inconsistency between slip rates decreases our confidence in our estimates of current fault activity along the southern San Andreas fault more than if we had just one slip rate; this is similar to the conundrum of having several clocks tell you different times.…”

Section: Introductionmentioning

confidence: 99%

Mechanical Analysis of Fault Slip Rate Sites within the San Gorgonio Pass Region, Southern California USA

Hatch

Cooke

Elston

2023

tekt

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Earthquake hazard assessments rely on observations from the field and geophysical data that provide fault slip rate estimates at specific sites and inform the geometry of active faults; however, uncertainty remains for both slip rate and geometry. Furthermore, incompatibilities between inferred fault geometry and geologic slip rates arise within crustal deformation models where model and geologic slip rates disagree. The impact of these incompatibilities may be local to sites or have wider effect on the fault system deformation. Here, we investigate the roles of structural position of sites and uncertainty of slip rates using three-dimensional mechanical models that simulate deformation across many earthquake cycles along southern San Andreas fault near the San Gorgonio Pass in California. Within the models, the impact of strike-slip rate sites on the fault system depends on their structural positions. Slip rates at sites along short and segmented faults has lesser impact on the slip along the fault system than either slip rates at sites along longer faults or at sites within fault branches. Consequently, inaccuracies in the slip rate estimates used for seismic hazard assessment may have differing impacts on the fault system depending on location and structural position of the slip rates. Fault branches along strike-slip faults warrant detailed investigation not only because these areas have high spatial variability of slip rate and accrue nearby off-fault deformation but also because changes in slip rates along branches has larger impact on deformation along fault system than other sites. Lack of data or large uncertainty in slip rate data from fault branches can affect our ability to accurately assess seismic hazard of the region.

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Non-steady-state slip rates emerge along evolving restraining bends under constant loading

Cited by 6 publications

References 28 publications

Mechanical Analysis of Fault Slip Rate Sites within the San Gorgonio Pass Region, Southern California USA

Mechanical Analysis of Fault Slip Rate Sites within the San Gorgonio Pass Region, Southern California USA

A validated geomechanical model for the strike-slip restraining bend in Lebanon

Mechanical Analysis of Fault Slip Rate Sites within the San Gorgonio Pass Region, Southern California USA

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