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| --- | ||
| templateKey: model | ||
| slug: sandifordcraig-2023-subduction | ||
| title: Plate bending earthquakes and the strength distribution of the lithosphere | ||
| date: '2024-05-28T00:11:12.000Z' | ||
| featuredpost: | ||
| for_codes: | ||
| - 370401 | ||
| status: | ||
| - None | ||
| doi: '' | ||
| url: https://mate.science//models/sandifordcraig-2023-subduction | ||
| creditText: '' | ||
| software: | ||
| - name: ASPECT v2.4.0 | ||
| doi: https://doi.org/10.5281/zenodo.6903424 | ||
| url_source: https://github.com/geodynamics/aspect | ||
| licence: | ||
| licence_url: https://creativecommons.org/licenses/by/4.0/legalcode | ||
| licence_image: ../../../img/licence/by.png | ||
| description: Creative Commons Attribution 4.0 International | ||
| licence_file: license.txt | ||
| submitter: | ||
| name: Dan | ||
| family_name: Sandiford | ||
| ORCID: https://orcid.org/0000-0002-2207-6837 | ||
| creators: | ||
| - name: Dan | ||
| family_name: Sandiford | ||
| ORCID: 0000-0002-2207-6837 | ||
| - name: Timothy J | ||
| family_name: Craig | ||
| ORCID: 0000-0003-2198-9172 | ||
| associated_publication: | ||
| authors: | ||
| - '@type': Person | ||
| '@id': http://orcid.org/0000-0002-2207-6837 | ||
| givenName: Dan | ||
| familyName: Sandiford | ||
| affiliation: | ||
| - '@type': Organization | ||
| name: School of Earth, Atmosphere and Environment, Monash University , Melbourne, | ||
| VIC 3800, Australia (formerly) | ||
| - '@type': Person | ||
| '@id': http://orcid.org/0000-0003-2198-9172 | ||
| givenName: Timothy J | ||
| familyName: Craig | ||
| affiliation: | ||
| - '@type': Organization | ||
| name: COMET, Institute of Geophysics and Tectonics, School of Earth and | ||
| Environment, University of Leeds , Leeds LS29JT, UK | ||
| title: Plate bending earthquakes and the strength distribution of the lithosphere | ||
| doi: http://dx.doi.org/10.1093/gji/ggad230 | ||
| url: '' | ||
| journal: Geophysical Journal International | ||
| publisher: Oxford University Press (OUP) | ||
| date: 2023-5-27 | ||
| compute_info: | ||
| name: Gadi Supercomputer | ||
| organisation: National Computational Infrastructure | ||
| url: https://pid.nci.org.au/doi/f5966_0057_9267_4579 | ||
| doi: https://doi.org/10.25914/608bfd1838db2 | ||
| research_tags: | ||
| - Dynamics of lithosphere | ||
| - Lithospheric flexure | ||
| - Subduction | ||
| - Earthquakes | ||
| compute_tags: | ||
| - C++ | ||
| - finite-element | ||
| - adaptive-mesh-refinement | ||
| - particles | ||
| funder: | ||
| - name: Australian Research Council | ||
| doi: https://ror.org/05mmh0f86 | ||
| - name: Royal Society | ||
| doi: https://ror.org/03wnrjx87 | ||
| - name: Natural Environment Research Council | ||
| doi: https://ror.org/02b5d8509 | ||
| funding: | ||
| - name: Australian Research Council | ||
| doi: https://ror.org/05mmh0f86 | ||
| number_id: DP150102887 | ||
| - name: Royal Society | ||
| doi: https://ror.org/03wnrjx87 | ||
| number_id: URF\R1\180088 | ||
| abstract: 'This study investigates the dynamics and constitutive behaviour of the | ||
| oceanic lithosphere as it bends and yields during subduction. Two main observational | ||
| constraints are considered: the maximum bending moment that can be supported by | ||
| the lithosphere, and the inferred neutral plane depth in bending. We particularly | ||
| focus on regions of old lithosphere where the ‘apparent’ neutral plane depth is | ||
| about 30 km. We use subduction modelling approaches to investigate these flexural | ||
| characteristics. We reassess bending moment estimates from a range of previous studies, | ||
| and show a significant convergence towards what we call the ‘intermediate’ range | ||
| of lithosphere strength: weaker than some classical models predict, but stronger | ||
| than recent inferences at seamounts. We consider the non-uniqueness that arises | ||
| due to the trade-offs in strength as well background (tectonic) stress state. We | ||
| outline this problem with several end-member models, which differ in regard to relative | ||
| strength in the brittle and ductile regimes. We evaluate the consistency of these | ||
| models in terms of a range of constraints, primarily the seismic expression of the | ||
| outer rise. We show that a 30 km neutral plane depth implies that net slab pull | ||
| is not greater than about 2 TN m−1. In contrast, models with low brittle strength | ||
| imply that regions with a 30 km neutral plane depth are under moderate net axial | ||
| compression. Under these conditions, reverse faulting is predicted beneath the neutral | ||
| plane at depths >30 km. We show that moderate variations in background stress | ||
| have a large impact on the predicted anelastic dissipation. We suggest brittle reverse | ||
| faulting is a marginal phenomenon which may be inhibited by moderate changes in | ||
| background stress.' | ||
| description: Tectonic plates are recycled into the mantle through subduction, where | ||
| they bend and deform in various ways, such as brittle failure. This process creates | ||
| deep sea trenches and results in characteristic earthquake patterns and gravity | ||
| anomalies. In this study, we used a numerical model to investigate plate bending | ||
| dynamics, complementing simpler approaches like flexural yield strength envelopes. | ||
| We focused on the competition between bending stress and sources of net in-plane | ||
| stress, such as slab pull, which influences the plate's neutral plane depth. It | ||
| is difficult to reconcile the 'apparent' neutral plane depth with a net slab pull | ||
| force greater than about 2 TN/m. Deviatoric compression in subducting plates more | ||
| easily explains reverse earthquakes at depths of 20-50 km in the bending plate. | ||
| images: | ||
| landing_image: | ||
| src: ./graphics/res_fig_final_ann.png | ||
| caption: Downdip component of strain rate tensor and resolved stress difference | ||
| from the numerical model, focusing on features within the plate/slab. The resolved | ||
| stress difference is defined as ($\sigma_{s} - \sigma_{z}$), where $\hat{s}$, | ||
| and $\hat{z}$ are unit vectors in the downdip and slab normal directions. The | ||
| fields show, for example, shortening/extension in the downdip direction. Stress | ||
| profiles at four locations are shown. The blue line ($x_0$) is the first zero | ||
| crossing based on analysis of the flexural component of the topography. The | ||
| black line is the location of maximum bending moment. | ||
| graphic_abstract: | ||
| src: ./graphics/gpe_fm26.png | ||
| caption: 'The main panel shows the variation in terms that arise in a 2D "vertically | ||
| integrated" form of the force balance (or stress equilibrium) equations. Assuming | ||
| a traction-free surface, the force balance states that across a horizontal section | ||
| of the lithosphere, the following terms must sum to zero: 1) integrated basal | ||
| shear traction, 2) the difference in the vertically-integrated deviatoric stress | ||
| and 3), the difference in the vertically-integrated vertical normal stress (often | ||
| called the GPE). In the figure, the overbar symbols represent vertical integration | ||
| across the lithosphere. Specifically, integration from a reference height, (taken | ||
| here as the mean ridge height) down to a reference depth (taken here as 150 | ||
| km beneath the reference height). In the main panel, the black line shows the | ||
| horizontal variation in the vertically integrated deviatoric stress difference | ||
| ($\tau_{xx} - \tau_{zz}$). Positive values indicate a state of deviatoric tension. | ||
| The dashed blue line shows the horizontal variation in the vertically integrated | ||
| vertical normal stress ($\sigma_{yy}$) (or the GPE). Strictly speaking, this | ||
| quantity is only equal to the GPE when the vertical normal stress is lithostatic, | ||
| but the term is retained in this study due to convention. The upper panel shows | ||
| the subducting plate topography at 2 different scales.' | ||
| model_setup: | ||
| src: ./graphics/s1a.png | ||
| caption: The main panel shows the full model domain and initial temperature field. | ||
| The texture is generated with a line integral convolution of the velocity field. | ||
| Contours show evolution of the slab during the 10 Myr simulation. Velocity arrows | ||
| show convergence rates at 5 Myr into the simulation. Inset panels show details | ||
| of the adaptive mesh refinement during the simulation. | ||
| animation: | ||
| src: ./graphics/animation | ||
| caption: 'Animation shows the model domain at 2x vertical exaggeration. The scalar | ||
| field is the effective strain rate, i.e. $\dot\epsilon_{II} = \sqrt{J2} = \sqrt{0.5(\dot\epsilon_{i,j}: | ||
| \epsilon_{i,j})}$. Upper panel shows the evolution of the model topography (a | ||
| true free surface). The topographic profile reveals the long-wavelength isostatic | ||
| thermal subsidence, as well as the flexural topography associated with the subduction | ||
| zone. The model exhibits a very short-wavelength instability in the free surface | ||
| of the over-riding plate, which begins approximately 3 Ma after the start of the | ||
| simulation.' | ||
| model_setup_info: | ||
| url: '' | ||
| summary: The subduction model comprises a rectangular domain with a depth of 2900 | ||
| km, and an aspect ratio of 4. The initial conditions comprise an adiabatic mantle | ||
| with a potential temperature of 1350 C and two plates, whose age and thermal structure | ||
| follows the cooling 1d cooling profile for a half-space (infinite in the depth | ||
| direction). One of these plates is attached to a slab that extends to 660 km depth, | ||
| and has an age of 100 Myr at the trench. The upper plate is modelled with a younger | ||
| thermal age, 25 Myr at the trench. Imposing an initial slab that reaches the transition | ||
| zone was found to be a more stable initial configuration in terms of instabilities | ||
| of the free surface. 7 levels of mesh refinement were used, with the largest (Q2) | ||
| elements having an edge length of 45 km, and the smallest elements have an edge | ||
| length of ∼ 700 m. The interface is modelled through an entrained weak layer approach. | ||
| A thin layer (here 2 km thick) represented by a separate composition is imposed | ||
| on the top of the subducting plate, as well as between the subducting slab and | ||
| upper plate. This composition has a low coefficient of friction, providing a shear | ||
| stress that varies between between about 10 - 20 MPa throughout the plate interface | ||
| domain. See the included model input file (.prm) for further details. | ||
| model_files: | ||
| url: '' | ||
| notes: Model setup is provided by an ASPECT input file and a WorldBuilder file (https://github.com/GeodynamicWorldBuilder/WorldBuilder). | ||
| Minor modifications to the ASPECT source code were implemented and are discussed | ||
| in the associated publication as well as the `model_code_inputs/README.md` directory. | ||
| file_tree: '' | ||
| existing_identifier: https://github.com/dansand/subduction_GJI2022 | ||
| nci_file_path: | ||
| https://thredds.nci.org.au/thredds/catalog/nm08/MATE/sandifordcraig-2023-subduction/catalog.html | ||
| include: true | ||
| dataset: | ||
| url: '' | ||
| notes: "Computations were done using the ASPECT code version 2.4.0. ASPECT output | ||
| data from 2 simulations are included with this model. The reference model is the | ||
| same model setup/data described in Sandiford and Craig, (2023). An alternative | ||
| model is included in which the over-riding plate is welded to the left sidewall | ||
| at the start of the simulation (whereas the initial temperature field in the reference | ||
| model has a ridge). Note that both simulations develop a short-wavelength instability | ||
| in the free surface of the over-riding plate, which begins approximately 3 Ma | ||
| after the start of the simulation. The top level directories contains typical | ||
| ASPECT output files, including log.txt and restart files. The primary output data | ||
| consists of:\r\n\r\n- plain text files representing model topography (e.g. topography.00000)\r | ||
| \n- a range of \"field\" data, in .vtu format in the `./solution` sub-directory | ||
| (e.g. solution-00000.0000.vtu). At each output step, there are 48 vtu files written. | ||
| These can be opened with Paraview using the solution.pvd file in the top level. | ||
| Quantities generally have SI units. Velocities are output as meters/year. \r\n\ | ||
| - particle information stored as .vtu files (16 per timestep). Particles were | ||
| used to track the 2-km-thick weak entrained layer that facilitates the plate interface | ||
| decoupling zone." | ||
| existing_identifier: '' | ||
| nci_file_path: | ||
| https://thredds.nci.org.au/thredds/catalog/nm08/MATE/sandifordcraig-2023-subduction/catalog.html | ||
| include: true | ||
| metadataFile: ro-crate-metadata.json | ||
| --- |