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arxiv: 1906.08527 · v1 · pith:MKXO4CAXnew · submitted 2019-06-20 · ⚛️ physics.geo-ph

Rough Subducting Seafloor Reduces Interseismic Coupling and Mega-Earthquake Occurrence: Insights From Analogue Models

Elenora Van Rijsingen , Francesca Funiciello , Fabio Corbi , Serge Lallemand This is my paper

Pith reviewed 2026-05-25 19:22 UTC · model grok-4.3

classification ⚛️ physics.geo-ph
keywords subduction zonesinterface roughnessanalogue modelsinterseismic couplingmegathrust earthquakesseafloor roughnessseismicity
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The pith

Rough subduction interfaces reduce megathrust coupling and limit mega-earthquake size in analogue models.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper uses analogue models to compare subduction zones with very rough versus smooth interfaces. It finds that rough interfaces have lower frictional strength and interseismic coupling. Ruptures on rough interfaces are smaller in area, duration, and displacement, with the interface segmented by the roughness. This matters because it links seafloor roughness to the potential for large earthquakes in real subduction zones.

Core claim

Models characterized by a very rough interface have lower interface frictional strength and lower interseismic coupling than models with a smooth interface. Overall, ruptures in the rough models have smaller rupture area, duration and mean displacement. Individual slip distributions indicate a segmentation of the subduction interface by the rough geometry. Flexure of the overriding plate is proposed as one mechanism contributing to the heterogeneous strength distribution.

What carries the argument

Seismotectonic analogue models comparing rough and smooth subduction interfaces, which demonstrate heterogeneous strength distribution and reduced coupling due to roughness.

If this is right

  • Rough interfaces produce lower interseismic coupling than smooth ones.
  • Ruptures have smaller area, duration, and mean displacement.
  • The rough geometry segments the interface, leading to heterogeneous slip distributions.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Subduction zones with smoother seafloor may be more prone to mega-earthquakes if roughness controls coupling.
  • Plate flexure effects on strength could be isolated in follow-up models that vary overriding plate thickness.
  • Field measurements of coupling differences between rough and smooth natural zones would test the scaling from the models.

Load-bearing premise

The analogue models accurately reproduce the stress state and scaling of natural subduction megathrusts, including the effects of plate flexure on interface strength.

What would settle it

Direct comparison of interseismic coupling measurements from GPS data in natural subduction zones with rough versus smooth subducting seafloor.

Figures

Figures reproduced from arXiv: 1906.08527 by Elenora Van Rijsingen, Fabio Corbi, Francesca Funiciello, Serge Lallemand.

Figure 1
Figure 1. Figure 1: Model setup with two endmember interfaces. a) Cartoon illustrating the rough and smooth endmembers. b) Schematic representation (top view) of the experimental setup. The rough interface (black squares), the seismogenic zone (blue shaded rectangle) and the trench (red triangles) are indicated. c) Photograph of the experimental apparatus (oblique view). The inset shows a zoom on the small-scale roughness res… view at source ↗
Figure 2
Figure 2. Figure 2: Cumulative displacement of one point centered above the seismogenic zone for each experiment. Each colored line represents one experiment, while the black line indicates the movement of the downgoing plate [PITH_FULL_IMAGE:figures/full_fig_p006_2.png] view at source ↗
Figure 5
Figure 5. Figure 5: Schematic sketch of flexure of the overriding plate (highlighted by the black arrows) due to the rough geometry of the interface, topview (a) and sideview (b). Due to the dipping subducting plate, the flexure in the wedge will be larger along leading flanks of the seamounts. The tensional forces resulting from the flexure superimpose on the global wedge contraction (not depicted above) as basal shear under… view at source ↗
read the original abstract

The roughness of the subduction interface is thought to influence seismogenic behavior in subduction zones, but a detailed understanding of how such roughness affects the state of stress along the subduction megathrust is still debated. Here, we use seismotectonic analogue models to investigate the effect of subduction interface roughness on seismicity in subduction zones. We compared analogue earthquake source parameters and slip distributions for two roughness endmembers. Models characterized by a very rough interface have lower interface frictional strength and lower interseismic coupling than models with a smooth interface. Overall, ruptures in the rough models have smaller rupture area, duration and mean displacement. Individual slip distributions indicate a segmentation of the subduction interface by the rough geometry. We propose that flexure of the overriding plate is one of the mechanisms that contribute to the heterogeneous strength distribution, responsible for the observed seismic behavior.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The manuscript uses seismotectonic analogue models to compare subduction megathrust behavior for smooth versus very rough interface end-members. It reports that rough-interface models exhibit lower interface frictional strength and interseismic coupling, with ruptures showing smaller area, duration, and mean displacement; slip distributions indicate interface segmentation by roughness, and overriding-plate flexure is proposed as one mechanism producing heterogeneous strength.

Significance. If the analogue scaling holds, the work supplies direct experimental evidence that seafloor roughness can segment the megathrust, reduce coupling, and limit mega-earthquake size—observations that are difficult to obtain from natural data alone. The ability to visualize full slip distributions across repeated events is a clear strength of the analogue approach and could inform interpretations of coupling maps and paleoseismic records in subduction zones with varying basement roughness.

major comments (2)
  1. [Abstract and Discussion] The central claim that rough models have lower frictional strength and coupling rests on the assumption that the analogue setup reproduces the stress state and scaling of natural megathrusts, including plate-flexure effects invoked in the abstract. No dimensionless analysis, stress-state comparison, or scaling checks are described that would confirm this reproduction; without them the reported differences cannot be confidently extrapolated beyond the laboratory.
  2. [Results] Results: the reported differences in coupling coefficient, rupture area, duration, and mean displacement between the two roughness end-members are presented without error bars, standard deviations across realizations, or statistical tests. This makes it impossible to judge whether the differences are robust to model variability or specific to the chosen material properties and loading rates.
minor comments (2)
  1. [Figures] Figure captions should explicitly state the roughness amplitude and wavelength values used for each end-member and the number of experimental runs performed for each case.
  2. [Methods] The term 'interseismic coupling' is used for the analogue models; a brief clarification of how this quantity is defined and measured from the laboratory time series would aid readers unfamiliar with the method.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their constructive comments, which highlight important aspects of our analogue modeling study. We respond to each major comment below.

read point-by-point responses

  1. Referee: [Abstract and Discussion] The central claim that rough models have lower frictional strength and coupling rests on the assumption that the analogue setup reproduces the stress state and scaling of natural megathrusts, including plate-flexure effects invoked in the abstract. No dimensionless analysis, stress-state comparison, or scaling checks are described that would confirm this reproduction; without them the reported differences cannot be confidently extrapolated beyond the laboratory.

    Authors: We agree that an explicit dimensionless analysis and stress-state comparison were not included in the original manuscript. In revision we will add a dedicated scaling section that presents the relevant non-dimensional numbers (e.g., force ratios governing gravitational, frictional and viscous stresses) and compares the modeled interface stresses and overriding-plate flexure magnitudes to typical natural values reported in the literature. The flexure mechanism itself is observed directly in the experiments and is offered as one contributing process; the added scaling discussion will clarify the conditions under which the laboratory results can be extrapolated. revision: yes

  2. Referee: [Results] Results: the reported differences in coupling coefficient, rupture area, duration, and mean displacement between the two roughness end-members are presented without error bars, standard deviations across realizations, or statistical tests. This makes it impossible to judge whether the differences are robust to model variability or specific to the chosen material properties and loading rates.

    Authors: The original manuscript reports results from repeated experiments for each roughness end-member, yet quantitative variability measures were omitted. In the revised version we will include standard deviations (or error bars) on the reported parameters and add a short statistical comparison (e.g., two-sample t-tests) between the smooth and rough populations to demonstrate that the observed differences are robust across realizations. revision: yes

Circularity Check

0 steps flagged

No significant circularity; purely experimental comparison

full rationale

The paper reports direct observations from analogue models comparing two roughness end-members. Central claims (lower frictional strength, lower coupling, smaller ruptures in rough models) are empirical outcomes of the physical experiments, with no derivations, fitted parameters renamed as predictions, or load-bearing self-citations. The study is self-contained against external benchmarks as an experimental result set; no equations or ansatzes reduce the findings to inputs by construction.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central observations rest on the untested premise that the laboratory models scale to Earth and that the chosen roughness endmembers bracket natural conditions; no free parameters are explicitly fitted in the abstract, but material and geometric choices function as implicit parameters.

axioms (1)
  • domain assumption Analogue models can be scaled to reproduce the stress state and rupture behavior of natural subduction megathrusts
    Invoked by the decision to compare model earthquake source parameters directly to real subduction zones

pith-pipeline@v0.9.0 · 5691 in / 1166 out tokens · 20568 ms · 2026-05-25T19:22:32.699112+00:00 · methodology

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Reference graph

Works this paper leans on

2 extracted references · 2 canonical work pages

  1. [1]

    https://doi.org/10.1130/G37258.1 Husen, S., Kissling, E., & Quintero, R. (2002). Tomographic evidence for a subducted seamount beneath the Gulf of Nicoya, Costa Rica: The cause of the 1990 Mw = 7.0 Gulf of Nicoya earthquake. Geophysical Research Letters, 29(8), 79-1-79–4. https://doi.org/10.1029/2001GL014045 Kelleher, J., & McCann, W. (1976). Buoyant Zone...

    work page doi:10.1130/g37258.1 2002

  2. [2]

    Roma Tre

    https://doi.org/10.1130/0091-7613(1997)025<0487:TEOSSO>2.3.CO;2 Singh, S. C., Hananto, N., Mukti, M., Robinson, D. P., Das, S., Chauhan, A., … Harjono, H. (2011). Aseismic zone and earthquake segmentation associated with a deep subducted seamount inSumatra. Nature Geoscience, 4(5), 308–311. https://doi.org/10.1038/ngeo1119 Thielicke, W., & Stamhuis, E. J....

    work page doi:10.1130/0091-7613(1997)025 1997