Dependence of seismic coupling on normal fault style along the <scp>N</scp>orthern <scp>M</scp>id‐<scp>A</scp>tlantic <scp>R</scp>idge

Olive, Jean‐Arthur; Escartı́n, J.

doi:10.1002/2016gc006460

Cited by 34 publications

(23 citation statements)

References 99 publications

(233 reference statements)

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“…Cowie et al () found the coupling coefficient for faults bounding the fast‐spreading East Pacific Rise to be less than 0.01. By contrast, estimates derived using teleseismic and hydroacoustic data from the slow‐spreading Mid‐Atlantic Ridge indicate coupling coefficients of 0.1–0.3 for symmetric ridge segments and 0.4–0.6 for segments characterized by the presence of large‐offset detachment faults (Olive & Escartín, ). Frohlich and Wetzel () found a similar systematic variation in the coupling coefficient across a range of spreading rates using teleseismic moment release rates.…”

Section: Introductionmentioning

confidence: 96%

“…Several studies have also addressed seismic behavior and the potential for aseismic slip on faults at divergent plate boundaries (e.g., Biemiller & Lavier, ; Calais et al, ; Cowie et al, ; Olive & Escartín, ; Sobolev & Rundquist, ). Observations support a range of behavior from seismic and aseismic fault slip across different ridges and ridge segments (Cowie et al, ; Olive & Escartín, ). However, interpretation of these variations has been limited due to the lack of quantitative models for seismic cycles on mid‐ocean ridge normal faults.…”

Section: Introductionmentioning

confidence: 99%

“…Frohlich and Wetzel () found a similar systematic variation in the coupling coefficient across a range of spreading rates using teleseismic moment release rates. Moreover, the variation in coupling with spreading rate appears to be robust even with the uncertainty introduced by assumptions regarding fault geometry and magmatism (Olive & Escartín, ). Several of these studies suggested that variations in fault thermal structure and the size of the seismogenic zone are responsible for the range of seismic coupling coefficients observed across different ridge spreading rates (Cowie et al, ; Solomon et al, ).…”

Section: Introductionmentioning

confidence: 99%

“…However, they did not address the specific reason why faults near fast‐spreading mid‐ocean ridges may be more prone to slipping aseismically when they are also known to occasionally generate moderately large earthquakes (e.g., M w ~5–6 along the East Pacific Rise, Ekström et al, ). To date, tests of such hypotheses (e.g., Olive & Escartín, ) have relied on extrapolation of rate‐and‐state models for strike‐slip faults (e.g., Liu et al, ) to normal fault systems, thus precluding a quantitative assessment of the effects of normal fault geometry on seismic coupling.…”

Section: Introductionmentioning

confidence: 99%

“…Seismic moment release rate at divergent plate boundaries normalized by boundary length and spreading rate (a proxy proportional to the seismic coupling coefficient; Frohlich & Wetzel, ; Olive & Escartín, ), plotted against spreading rate and seismogenic layer thickness. Seismogenic layer thickness estimated from the on‐axis depth of the 600 °C isotherm as predicted by the model of Montési and Behn ().…”

Section: Introductionmentioning

confidence: 99%

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Controls on Mid‐ocean Ridge Normal Fault Seismicity Across Spreading Rates From Rate‐and‐State Friction Models

et al. 2018

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Recent seismic and geodetic observations have led to a growing realization that a significant amount of fault slip at plate boundaries occurs aseismically and that the amount of aseismic slip varies across tectonic settings. Seismic moment release rates measured along the fast‐spreading East Pacific Rise suggest that the majority of fault slip occurs aseismically. By contrast, at the slow‐spreading Mid‐Atlantic Ridge seismic slip may represent up to 60% of total fault displacement. In this study, we use rate‐and‐state friction models to quantify the seismic coupling coefficient, defined as the fraction of total fault slip that occurs seismically, on mid‐ocean ridge normal faults and investigate controls on fault behavior that might produce variations in coupling observed at oceanic spreading centers. We find that the seismic coupling coefficient scales with the ratio of the downdip width of the seismogenic area (W) to the critical earthquake nucleation size (h*). At mid‐ocean ridges, W is expected to increase with decreasing spreading rate. Thus, the relationship between seismic coupling and W/h* predicted from our models explains the first‐order variations in seismic coupling coefficient as a function of spreading rate.

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Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Controls on Mid‐ocean Ridge Normal Fault Seismicity Across Spreading Rates From Rate‐and‐State Friction Models

et al. 2018

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Tectonic structure, evolution, and the nature of oceanic core complexes and their detachment fault zones (13°20′N and 13°30′N, Mid Atlantic Ridge)

Escartı́n

Mével

Petersen

et al. 2017

Geochem Geophys Geosyst

107

179

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Microbathymetry data, in situ observations, and sampling along the 13°20′N and 13°20′N oceanic core complexes (OCCs) reveal mechanisms of detachment fault denudation at the seafloor, links between tectonic extension and mass wasting, and expose the nature of corrugations, ubiquitous at OCCs. In the initial stages of detachment faulting and high‐angle fault, scarps show extensive mass wasting that reduces their slope. Flexural rotation further lowers scarp slope, hinders mass wasting, resulting in morphologically complex chaotic terrain between the breakaway and the denuded corrugated surface. Extension and drag along the fault plane uplifts a wedge of hangingwall material (apron). The detachment surface emerges along a continuous moat that sheds rocks and covers it with unconsolidated rubble, while local slumping emplaces rubble ridges overlying corrugations. The detachment fault zone is a set of anostomosed slip planes, elongated in the along‐extension direction. Slip planes bind fault rock bodies defining the corrugations observed in microbathymetry and sonar. Fault planes with extension‐parallel stria are exposed along corrugation flanks, where the rubble cover is shed. Detachment fault rocks are primarily basalt fault breccia at 13°20′N OCC, and gabbro and peridotite at 13°30′N, demonstrating that brittle strain localization in shallow lithosphere form corrugations, regardless of lithologies in the detachment zone. Finally, faulting and volcanism dismember the 13°30′N OCC, with widespread present and past hydrothermal activity (Semenov fields), while the Irinovskoe hydrothermal field at the 13°20′N core complex suggests a magmatic source within the footwall. These results confirm the ubiquitous relationship between hydrothermal activity and oceanic detachment formation and evolution.

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Seismicity properties of the Chain Transform Fault inferred using data from the PI-LAB experiment

Leptokaropoulos

Rychert

Harmon

et al. 2022

Preprint

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Oceanic transform faults (TFs) are steeply dipping fault segments of young oceanic lithosphere bounded between mid-ocean ridge spreading centers. They are thought to have a simple structure in comparison to their continental counterparts given that the composition of the ocean crust and upper mantle is relatively homogenous and generally lacks the complex lateral variability commonly evident in the continental crust (e.g., Behn et al., 2007;Wolfson-Schwehr & Boettcher, 2019). Along the axis of an oceanic TF, lithospheres of different age, and thus with different thermal and mechanical properties, interact.Ridge-transform plate boundaries may also enhance hydrothermal circulation, substantially impacting geophysical, geochemical, and biological processes (e.g., Hensen et al., 2019). Such phenomena are plausibly very typical in marine transform systems. TFs themselves may exhibit fault zone damage which can also contribute to hydrothermal circulation and alteration along the transform valley (Froment et al., 2014;Kohli et al., 2021). Exposure of altered peridotites and gabbro at detachment faults along fracture zones and core complexes (Blackman Abstract Oceanic transform faults are intriguing in that they do not produce earthquakes as large as might be expected given their dimensions. We use 1-year of local seismicity (370 events above M C = 2.3) recorded on an array of ocean bottom seismometers (OBSs) and geophysical data to study the seismotectonic properties of the Chain transform, located in the equatorial Mid-Atlantic. We extend our analysis back in time by considering stronger earthquakes (M W ≥ 5.0) from global catalogs. We divide Chain into three areas (east, central, and west) based on historical event distribution, morphology, and multidimensional OBS seismicity cluster analysis. Seismic activity recorded by the OBS is the highest at the eastern area of Chain where there is a lozenge-shaped topographic high, a negative rMBA gravity anomaly, and only a few historical M W ≥ 5.5 events. OBS seismicity rates are lower in the western and central areas. However, these areas accommodate the majority of seismic moment release, as inferred from both OBS and historical data. Higher b-values are significantly correlated with lower rMBA and with shallower bathymetry, potentially related to thickened crust. Our results suggest high lateral heterogeneity along Chain. Patches with moderate to low OBS seismicity rates that occasionally host M W ≥ 6.0 earthquakes are interrupted by segments with abundant OBS activity but few historical events with 5.5 ≤ M W < 6.0. This segmentation is possibly due to variable fluid circulation and alteration, which may also change in time.Plain Language Summary Oceanic transform faults (TFs) typically host earthquakes much smaller than expected based on their total seismogenic area. We study the seismotectonic properties of the Chain TF by combining 1-year of seismicity recorded by an ocean bottom seismometer (OBS) array with geophysical data (bathymetry, tidal height, gravity anomalies)...

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Dependence of seismic coupling on normal fault style along the Northern Mid‐Atlantic Ridge

Cited by 34 publications

References 99 publications

Controls on Mid‐ocean Ridge Normal Fault Seismicity Across Spreading Rates From Rate‐and‐State Friction Models

Controls on Mid‐ocean Ridge Normal Fault Seismicity Across Spreading Rates From Rate‐and‐State Friction Models

Tectonic structure, evolution, and the nature of oceanic core complexes and their detachment fault zones (13°20′N and 13°30′N, Mid Atlantic Ridge)

Seismicity properties of the Chain Transform Fault inferred using data from the PI-LAB experiment

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