Do Coupled Megathrusts Rupture?
Description:
To assess seismic hazard along subduction zones, which host Earth’s largest earthquakes, geodesists routinely measure interseismic surface deformation rates and invert them to estimate distributions of slip deficit along the plate interface. The resulting kinematic geodetic coupling models highlight portions of the megathrust that are “locked” and accumulating strain, thus identifying likely candidates for future rupture. However, these models are limited by sparse offshore observations, which lead to large uncertainties in shallow coupling, and by growing evidence that coupling can vary substantially over just a few years, undermining the assumption that coupling remains constant over interseismic periods. Moreover, high coupling is not a prerequisite for earthquake rupture, as dynamic slip can propagate through creeping regions while strongly coupled segments may instead act as rupture barriers.
To evaluate whether, and to what extent, geodetically inferred coupling correlates with coseismic slip, we perform a global comparison of slip deficit models and finite-fault slip distributions. We compile the first unified dataset of coupling models including twelve subduction zones and 61 finite-fault models of megathrust earthquakes that ruptured these margins, with a cumulative moment magnitude of 470. We discretize each slip model into a point cloud reflecting its slip distribution, allowing us to quantitatively link slip with coupling values to evaluate their correlation.
Our slip-coupling analysis reveals consistent global patterns: large megathrust earthquakes (Mw ≥ 7.5) preferentially rupture highly coupled regions, whereas smaller events show weaker coupling-slip correlations. Comparison with the null hypothesis in which slip-coupling correlation is completely random highlight that observed slip-coupling correlations are statistically significant. These findings highlight the complex interplay between coupling and rupture behavior, demonstrating that strong coupling alone does not unequivocally predict future earthquake slip patterns.
Session: Linking Subduction Zone Processes and Cascading Hazards in Alaska, Cascadia, Chile and Beyond - II
Type: Oral
Date: 4/16/2026
Presentation Time: 03:00 PM (local time)
Presenting Author: Alice Gabriel
Student Presenter: No
Invited Presentation:
Poster Number:
Authors
Bar Oryan bar.oryan@columbia.edu University of California, San Diego |
Alice Gabriel Presenting Author Corresponding Author algabriel@ucsd.edu University of California, San Diego |
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Do Coupled Megathrusts Rupture?
Category
Linking Subduction Zone Processes and Cascading Hazards in Alaska, Cascadia, Chile and Beyond