How geometry of subduction zones correlates with earthquake dynamics

Gary P. T. Choi; L. Mahadevan; Oscar Y. L. Chau; Rebecca Bendick

arxiv: 2606.02520 · v1 · pith:HQSMUCVGnew · submitted 2026-06-01 · ⚛️ physics.geo-ph

How geometry of subduction zones correlates with earthquake dynamics

Oscar Y. L. Chau , Rebecca Bendick , Gary P. T. Choi , L. Mahadevan This is my paper

Pith reviewed 2026-06-28 11:28 UTC · model grok-4.3

classification ⚛️ physics.geo-ph

keywords subduction zonesearthquake dynamicsslab curvaturemegathrust earthquakesplate geometryseismic productivitydifferential geometry

0 comments

The pith

Weakly curved subduction zones produce rarer but larger earthquakes while curved ones produce frequent smaller events.

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

The paper tests whether the geometry of subduction zones shapes earthquake patterns by linking interface curvature to stress buildup and release. A scaling argument predicts that flat zones allow stress to accumulate for infrequent large events while curved zones promote more frequent smaller releases. Analysis of global datasets using surface curvature metrics from differential geometry confirms that weakly curved slabs associate with larger but rarer events and zones with high curvature dispersion associate with frequent smaller events. The results tie earthquake productivity to the conformability between overriding and downgoing plates. This leads to the suggestion that large-scale geometry belongs in models of seismic risk.

Core claim

Weakly curved slab geometries are associated with rarer larger magnitude events, while slab geometries with a larger relative dispersion in curvature are associated with frequent but smaller magnitude events. The analysis shows that earthquake productivity depends on the conformability of the overriding and downgoing plates as measured by scale-dependent shape metrics of the subduction zones.

What carries the argument

Surface curvature metrics from differential geometry of subduction zone slabs, combined with a scaling argument that curvature alters stress accumulation and release relative to planar interfaces.

If this is right

Conformable sliding along relatively flat zones leads to rare but large events.
Curved zones lead to frequent smaller events due to more distributed stress release.
Earthquake productivity depends on the relative dispersion in curvature across the interface.
Computational models of subduction must incorporate large-scale slab geometry to capture observed seismic patterns.

Where Pith is reading between the lines

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

Curvature monitoring over time could reveal whether geometric changes precede shifts in seismic regime.
The same curvature-dispersion logic might apply to other large curved fault systems outside subduction zones.
Numerical simulations that vary only slab curvature while holding other parameters fixed could isolate its contribution to event size and frequency.

Load-bearing premise

The scaling argument that curvature changes stress accumulation and release relative to planar interfaces applies to real subduction zone dynamics.

What would settle it

A dataset of global subduction zones in which measured curvatures show no statistical link to the observed frequency-magnitude distributions of earthquakes would falsify the central correlation.

Figures

Figures reproduced from arXiv: 2606.02520 by Gary P. T. Choi, L. Mahadevan, Oscar Y. L. Chau, Rebecca Bendick.

**Figure 1.** Figure 1: Subduction zone models and their surface curvatures. (a) The locations of the 13 subduction zone models considered in this study: Aleutians (alu), Central America (cam), Cascadia (cas), Izu-Bonin (izu), Kermadec (ker), Kuril (kur), Philippines (phi), Ryukyu (ryu), South America (sam), Scotia (sco), Solomon Islands (sol), Sumatra/Java (sum), and Vanuatu (van), with a zoom-in at kur and sco color-coded with … view at source ↗

**Figure 2.** Figure 2: Correlation between surface curvature and the maximum historically observed magnitude of earthquakes Mmax. (a) The average absolute Gaussian curvature mean(|K|). (b) The average absolute mean curvature mean(|H|). Each point represents one slab model, and the red line is the best-fit straight line. The new Petropavlovsk-Kamchatsky event (kam) is highlighted in blue. See the caption of [PITH_FULL_IMAGE:figu… view at source ↗

**Figure 3.** Figure 3: Correlation between coefficient of variation of |K| and the number of occurrence of earthquakes. Each point represents one slab model, and the red line is the best-fit straight line. See the caption of [PITH_FULL_IMAGE:figures/full_fig_p007_3.png] view at source ↗

read the original abstract

Subduction zones on the surface of the Earth, where abrupt sliding leads to earthquakes, are generally curved and localized. How does the geometry of these zones influence the occurrence of megathrust earthquakes? Here we use a combination of simple scaling arguments and data analysis using the differential geometry of surfaces to examine the relationship between the earthquake productivity of subduction zones and their shape. A scaling argument suggests how interface curvature changes both the accumulation and release of stress relative to planar interfaces; conformable sliding along relatively flat subduction zones should lead to rare but large events, while curved subduction zones should lead to frequent smaller events. To test this, we leverage global geometry datasets and analyze the correlation between the surface curvatures of the subduction zones and the frequency and magnitude of earthquakes therein. Our analysis shows that weakly curved slab geometries are associated with rarer larger magnitude events, while slab geometries with a larger relative dispersion in curvature are associated with frequent but smaller magnitude events. Using different scale-dependent shape metrics of the subduction zones, we show that the earthquake productivity is influenced by the conformability of the overriding and downgoing plates. More broadly, our results suggest the need to incorporate the large-scale geometry of subduction zones in computational models and predictive frameworks for earthquake risk.

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.

Desk Editor's Note private letter to a colleague

The curvature-quake correlations are reported but rest on uncontrolled associations that length and convergence rate could explain.

read the letter

The main thing to know is that the paper links subduction zone curvature metrics to earthquake frequency and size using global data and a scaling argument, but the central claim is open to simple confounding.

They start with a qualitative scaling idea that curvature alters stress accumulation and release relative to flat interfaces, then apply differential geometry to quantify mean curvature and its dispersion across slabs. The data analysis finds that weakly curved zones match rarer large events while high relative dispersion matches frequent small ones, and they tie this to plate conformability. The global scope and the distinction between average shape and dispersion are the concrete advances.

The work is new in mapping those specific scale-dependent curvature measures onto quake productivity statistics. It does a clean job of turning an existing physical intuition into testable geometric descriptors without adding new mechanisms.

The soft spot is the missing controls. Subduction zone length scales the number of events observed and convergence rate scales stress input; both vary systematically with geometry. The abstract and scaling section give no indication of partial correlations, multivariate regression, or checks that the reported associations survive after accounting for these. Without that, the curvature signal cannot be cleanly separated from the covariates. The scaling argument itself stays qualitative and supplies no effect-size benchmark to compare against the data.

This is for geophysicists who model subduction dynamics or build hazard assessments and want geometric factors to test. A reader already working with differential geometry on earth data would get the most from the methods section.

It deserves peer review because the dataset is global and the question is practical, even though the statistics will need tightening.

Referee Report

3 major / 2 minor

Summary. The manuscript uses scaling arguments from differential geometry to propose that subduction zone curvature affects stress accumulation and release, predicting that weakly curved interfaces produce rare large-magnitude events while higher relative curvature dispersion produces frequent smaller events. It then reports correlations from global geometry and earthquake datasets supporting these patterns and concludes that plate conformability influences seismic productivity, calling for geometry to be incorporated into earthquake models.

Significance. If the reported correlations survive controls for known covariates and are shown to be robust, the work would supply a concrete, geometry-based mechanism linking interface shape to megathrust statistics, with direct implications for risk assessment frameworks that currently treat subduction zones largely as planar or one-dimensional features.

major comments (3)

[Abstract] Abstract: the scaling argument is stated qualitatively and supplies no effect-size estimate or predicted functional form that could be compared against the magnitude of known confounders such as subduction-zone length (which scales event counts) or convergence rate (which scales stress accumulation).
[Data analysis] Data analysis section: the reported associations between curvature metrics and earthquake frequency/magnitude are not shown to survive partial correlation or multivariate regression that controls for subduction-zone length and convergence rate; without such controls the central empirical claim cannot be attributed to curvature rather than these covariates.
[Methods] Methods: no description is given of how surface curvatures are computed from the global geometry datasets, what selection criteria are applied to subduction segments and earthquake catalogs, or which statistical tests establish the significance of the correlations, preventing verification that the data support the stated claim.

minor comments (2)

[Abstract] The phrase 'relative dispersion in curvature' is used without an explicit formula or normalization; a precise definition would improve reproducibility.
[Figures] Figure captions should state the exact number of subduction zones and events entering each correlation panel.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for these constructive comments, which identify key areas where the manuscript can be strengthened for clarity and robustness. We respond point-by-point below.

read point-by-point responses

Referee: [Abstract] Abstract: the scaling argument is stated qualitatively and supplies no effect-size estimate or predicted functional form that could be compared against the magnitude of known confounders such as subduction-zone length (which scales event counts) or convergence rate (which scales stress accumulation).

Authors: The scaling argument in the main text derives a directional prediction from differential geometry (stress accumulation and release modulated by mean and Gaussian curvature relative to planar cases), but does not supply a closed-form effect size. We will revise the abstract to state the predicted qualitative dependence (rarer large events for low-curvature conformable interfaces) and note that quantitative comparison with confounders is performed via the empirical correlations reported later in the paper. revision: yes
Referee: [Data analysis] Data analysis section: the reported associations between curvature metrics and earthquake frequency/magnitude are not shown to survive partial correlation or multivariate regression that controls for subduction-zone length and convergence rate; without such controls the central empirical claim cannot be attributed to curvature rather than these covariates.

Authors: We agree that raw correlations alone do not isolate curvature from length and convergence rate. In the revision we will add partial-correlation and multivariate-regression results that control for these covariates and report whether the curvature associations remain significant. This will either confirm the geometry effect or require qualification of the central claim. revision: yes
Referee: [Methods] Methods: no description is given of how surface curvatures are computed from the global geometry datasets, what selection criteria are applied to subduction segments and earthquake catalogs, or which statistical tests establish the significance of the correlations, preventing verification that the data support the stated claim.

Authors: The original submission omitted these details. The revised manuscript will contain an expanded Methods section specifying (i) the differential-geometry operators used to compute mean and Gaussian curvature from the global slab-surface datasets, (ii) the exact selection criteria applied to subduction segments and earthquake catalogs, and (iii) the correlation coefficients and significance tests employed. revision: yes

Circularity Check

0 steps flagged

No circularity: scaling argument is qualitative motivation; correlations are independent empirical measurements.

full rationale

The paper motivates a hypothesis with a qualitative scaling argument about curvature affecting stress accumulation/release, then tests it via separate differential-geometry analysis of global subduction-zone datasets against earthquake catalogs. No equations, fitted parameters, or self-citations are shown that reduce the reported correlations to definitional identities or post-hoc normalizations. The central result is an observed statistical association, not a quantity forced by the input metrics themselves. Confounders such as zone length are a separate validity concern, not a circularity issue.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Abstract-only; the central claim rests on one domain assumption about curvature-stress coupling and uses no explicitly listed free parameters or new entities.

axioms (1)

domain assumption Interface curvature changes both the accumulation and release of stress relative to planar interfaces
Invoked in the abstract as the basis for expecting different earthquake productivity in curved versus flat subduction zones.

pith-pipeline@v0.9.1-grok · 5755 in / 1189 out tokens · 29463 ms · 2026-06-28T11:28:47.120427+00:00 · methodology

discussion (0)

Reference graph

Works this paper leans on

18 extracted references · 1 canonical work pages

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J. A. Laravie, “Geometry and lateral strain of subducted plates in island arcs,”Geology, vol. 3, no. 9, pp. 484–486, 1975

1975
[2]

Geometry of subducted plates and island arcs viewed as a buckling problem,

B. Bayly, “Geometry of subducted plates and island arcs viewed as a buckling problem,” Geology, vol. 10, no. 12, pp. 629–632, 1982

1982
[3]

The curvature of Wadati-Benioff zones and the torsional rigidity of subducting plates,

M. Bevis, “The curvature of Wadati-Benioff zones and the torsional rigidity of subducting plates,”Nature, vol. 323, no. 6083, pp. 52–53, 1986

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[4]

Why subduction zones are curved,

L. Mahadevan, R. Bendick, and H. Liang, “Why subduction zones are curved,”Tectonics, vol. 29, no. 6, 2010

2010
[5]

Extreme localized exhumation at syntaxes initiated by subduction geometry,

R. Bendick and T. A. Ehlers, “Extreme localized exhumation at syntaxes initiated by subduction geometry,”Geophys. Res. Lett., vol. 41, no. 16, pp. 5861–5867, 2014

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Geometric controls on megathrust earthquakes,

S. M. Plescia and G. P. Hayes, “Geometric controls on megathrust earthquakes,”Geophys. J. Int., vol. 222, no. 2, pp. 1270–1282, 2020

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Subduction zone geometry modulates the megathrust earthquake cycle: Magnitude, recurrence, and variability,

J. Biemiller, A.-A. Gabriel, D. A. May, and L. Staisch, “Subduction zone geometry modulates the megathrust earthquake cycle: Magnitude, recurrence, and variability,”J. Geophys. Res. Solid Earth, vol. 129, no. 8, p. e2024JB029191, 2024

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Competition between roughness and strength for scale- dependent surfaces,

V. Lambert and E. E. Brodsky, “Competition between roughness and strength for scale- dependent surfaces,”Phys. Rev. E., vol. 111, no. 6, p. 065502, 2025

2025
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G. P. Hayes, D. J. Wald, and R. L. Johnson, “Slab1.0: A three-dimensional model of global subduction zone geometries,”J. Geophys. Res. Solid Earth, vol. 117, no. B1, 2012

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Q. Bletery, A. M. Thomas, A. W. Rempel, L. Karlstrom, A. Sladen, and L. De Barros, “Mega-earthquakes rupture flat megathrusts,”Science, vol. 354, no. 6315, pp. 1027–1031, 2016

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Slab2, a comprehensive subduction zone geometry model,

G. P. Hayes, G. L. Moore, D. E. Portner, M. Hearne, H. Flamme, M. Furtney, and G. M. Smoczyk, “Slab2, a comprehensive subduction zone geometry model,”Science, vol. 362, no. 6410, pp. 58–61, 2018

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[13]

Evolution of fault-surface roughness with slip,

A. Sagy, E. E. Brodsky, and G. J. Axen, “Evolution of fault-surface roughness with slip,” Geology, vol. 35, no. 3, pp. 283–286, 2007

2007
[14]

Roughness of fault surfaces over nine decades of length scales,

T. Candela, F. Renard, Y. Klinger, K. Mair, J. Schmittbuhl, and E. E. Brodsky, “Roughness of fault surfaces over nine decades of length scales,”J. Geophys. Res. Solid Earth, vol. 117, no. B8, 2012

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[15]

Constraints from fault roughness on the scale-dependent strength of rocks,

E. E. Brodsky, J. D. Kirkpatrick, and T. Candela, “Constraints from fault roughness on the scale-dependent strength of rocks,”Geology, vol. 44, no. 1, pp. 19–22, 2016. 9

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[16]

Static adhesion hysteresis in elastic structures,

E. Memet, F. Hilitski, Z. Dogic, and L. Mahadevan, “Static adhesion hysteresis in elastic structures,”Soft Matter, vol. 17, no. 10, pp. 2704–2710, 2021

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[17]

M. P. Do Carmo,Differential geometry of curves and surfaces: revised and updated second edition. Dover Publications, Garden City, NY, 2016

2016
[18]

Oceanic plateau and spreading ridge subduction accom- panying arc reversal in the Solomon Islands,

B. Taylor and E. K. Benyshek, “Oceanic plateau and spreading ridge subduction accom- panying arc reversal in the Solomon Islands,”Geochem. Geophys. Geosyst., vol. 25, no. 1, p. e2023GC011270, 2024. 10 Supplementary Information S1 Slab surface geometry In this work, we analyzed the slab surface geometry of different subduction zones using surface curvature...

work page arXiv 2024

[1] [1]

Geometry and lateral strain of subducted plates in island arcs,

J. A. Laravie, “Geometry and lateral strain of subducted plates in island arcs,”Geology, vol. 3, no. 9, pp. 484–486, 1975

1975

[2] [2]

Geometry of subducted plates and island arcs viewed as a buckling problem,

B. Bayly, “Geometry of subducted plates and island arcs viewed as a buckling problem,” Geology, vol. 10, no. 12, pp. 629–632, 1982

1982

[3] [3]

The curvature of Wadati-Benioff zones and the torsional rigidity of subducting plates,

M. Bevis, “The curvature of Wadati-Benioff zones and the torsional rigidity of subducting plates,”Nature, vol. 323, no. 6083, pp. 52–53, 1986

1986

[4] [4]

Why subduction zones are curved,

L. Mahadevan, R. Bendick, and H. Liang, “Why subduction zones are curved,”Tectonics, vol. 29, no. 6, 2010

2010

[5] [5]

Extreme localized exhumation at syntaxes initiated by subduction geometry,

R. Bendick and T. A. Ehlers, “Extreme localized exhumation at syntaxes initiated by subduction geometry,”Geophys. Res. Lett., vol. 41, no. 16, pp. 5861–5867, 2014

2014

[6] [6]

Geometric controls on megathrust earthquakes,

S. M. Plescia and G. P. Hayes, “Geometric controls on megathrust earthquakes,”Geophys. J. Int., vol. 222, no. 2, pp. 1270–1282, 2020

2020

[7] [7]

Subduction zone geometry modulates the megathrust earthquake cycle: Magnitude, recurrence, and variability,

J. Biemiller, A.-A. Gabriel, D. A. May, and L. Staisch, “Subduction zone geometry modulates the megathrust earthquake cycle: Magnitude, recurrence, and variability,”J. Geophys. Res. Solid Earth, vol. 129, no. 8, p. e2024JB029191, 2024

2024

[8] [8]

Competition between roughness and strength for scale- dependent surfaces,

V. Lambert and E. E. Brodsky, “Competition between roughness and strength for scale- dependent surfaces,”Phys. Rev. E., vol. 111, no. 6, p. 065502, 2025

2025

[9] [9]

Slab1.0: A three-dimensional model of global subduction zone geometries,

G. P. Hayes, D. J. Wald, and R. L. Johnson, “Slab1.0: A three-dimensional model of global subduction zone geometries,”J. Geophys. Res. Solid Earth, vol. 117, no. B1, 2012

2012

[10] [10]

OpenQuake engine: An open hazard (and risk) software for the global earthquake model,

M. Pagani, D. Monelli, G. Weatherill, L. Danciu, H. Crowley, V. Silva, P. Henshaw, L. Butler, M. Nastasi, L. Panzeri,et al., “OpenQuake engine: An open hazard (and risk) software for the global earthquake model,”Seismol. Res. Lett., vol. 85, no. 3, pp. 692–702, 2014

2014

[11] [11]

Mega-earthquakes rupture flat megathrusts,

Q. Bletery, A. M. Thomas, A. W. Rempel, L. Karlstrom, A. Sladen, and L. De Barros, “Mega-earthquakes rupture flat megathrusts,”Science, vol. 354, no. 6315, pp. 1027–1031, 2016

2016

[12] [12]

Slab2, a comprehensive subduction zone geometry model,

G. P. Hayes, G. L. Moore, D. E. Portner, M. Hearne, H. Flamme, M. Furtney, and G. M. Smoczyk, “Slab2, a comprehensive subduction zone geometry model,”Science, vol. 362, no. 6410, pp. 58–61, 2018

2018

[13] [13]

Evolution of fault-surface roughness with slip,

A. Sagy, E. E. Brodsky, and G. J. Axen, “Evolution of fault-surface roughness with slip,” Geology, vol. 35, no. 3, pp. 283–286, 2007

2007

[14] [14]

Roughness of fault surfaces over nine decades of length scales,

T. Candela, F. Renard, Y. Klinger, K. Mair, J. Schmittbuhl, and E. E. Brodsky, “Roughness of fault surfaces over nine decades of length scales,”J. Geophys. Res. Solid Earth, vol. 117, no. B8, 2012

2012

[15] [15]

Constraints from fault roughness on the scale-dependent strength of rocks,

E. E. Brodsky, J. D. Kirkpatrick, and T. Candela, “Constraints from fault roughness on the scale-dependent strength of rocks,”Geology, vol. 44, no. 1, pp. 19–22, 2016. 9

2016

[16] [16]

Static adhesion hysteresis in elastic structures,

E. Memet, F. Hilitski, Z. Dogic, and L. Mahadevan, “Static adhesion hysteresis in elastic structures,”Soft Matter, vol. 17, no. 10, pp. 2704–2710, 2021

2021

[17] [17]

M. P. Do Carmo,Differential geometry of curves and surfaces: revised and updated second edition. Dover Publications, Garden City, NY, 2016

2016

[18] [18]

Oceanic plateau and spreading ridge subduction accom- panying arc reversal in the Solomon Islands,

B. Taylor and E. K. Benyshek, “Oceanic plateau and spreading ridge subduction accom- panying arc reversal in the Solomon Islands,”Geochem. Geophys. Geosyst., vol. 25, no. 1, p. e2023GC011270, 2024. 10 Supplementary Information S1 Slab surface geometry In this work, we analyzed the slab surface geometry of different subduction zones using surface curvature...

work page arXiv 2024