Imbalanced Moment Release Within Subducting Plates During Initial Bending and Unbending
Publication Date
2022-03Journal Title
Journal of Geophysical Research: Solid Earth
ISSN
2169-9313
Publisher
American Geophysical Union (AGU)
Volume
127
Issue
3
Language
en
Type
Article
This Version
AO
VoR
Metadata
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Craig, T., Methley, P., & Sandiford, D. (2022). Imbalanced Moment Release Within Subducting Plates During Initial Bending and Unbending. Journal of Geophysical Research: Solid Earth, 127 (3) https://doi.org/10.1029/2021jb023658
Abstract
Abstract: Internal deformation within the downgoing plate in subduction zones to accommodate the bending of the plate as it starts to subduct is reflected in widespread intraplate seismicity. This seismicity, extending from the outer rise and outer trench slope down to intermediate depths within the slab, exhibits a wide variety of focal mechanism types, often indicative of the accumulation and recovery of down‐dip curvature through the combination of normal‐faulting and thrust‐faulting earthquakes. In the idealized case, where the bulk internal deformation is recovered and slabs descend as a straight plate into the deeper mantle, we might expect the seismic moment released in both extension and compression to balance. However, a number of factors may complicate this: the thermal, compositional, and rheological evolution of the slab as it subducts, changes in the proportion of deformation accommodated seismically, and whether the slab undergoes any permanent deformation. These factors may result in intraslab deformation and seismicity unrelated to the slab curvature. Here, we assess earthquake moment release in intraslab settings around the world, focusing on those subduction systems with relatively simple slab geometries. Consideration of several regions around the western Pacific and eastern Indian Ocean indicates that substantially more deformation is accommodated seismically during bending than during unbending, and that in both settings, significantly more moment release reflects down‐dip extension than down‐dip compression. This suggests that, although the location of seismicity is clearly related to changes in slab curvature, there is a component of permanent, unrecovered down‐dip extension in many subducting slabs.
Keywords
Seismology, EXPLORATION GEOPHYSICS, Gravity methods, GEOCHEMISTRY, Subduction zone processes, GEODESY AND GRAVITY, Transient deformation, Tectonic deformation, Time variable gravity, Gravity anomalies and Earth structure, Satellite geodesy: results, Seismic cycle related deformations, HYDROLOGY, Estimation and forecasting, INFORMATICS, Forecasting, IONOSPHERE, MAGNETOSPHERIC PHYSICS, MARINE GEOLOGY AND GEOPHYSICS, MATHEMATICAL GEOPHYSICS, Prediction, Probabilistic forecasting, MINERALOGY AND PETROLOGY, OCEANOGRAPHY: GENERAL, Ocean predictability and prediction, NATURAL HAZARDS, Monitoring, forecasting, prediction, POLICY SCIENCES, RADIO SCIENCE, Interferometry, Ionospheric physics, SEISMOLOGY, Seismicity and tectonics, Subduction zones, Continental crust, Earthquake dynamics, Earthquake source observations, Earthquake interaction, forecasting, and prediction, SPACE WEATHER, Policy, TECTONOPHYSICS, Lithospheric flexure, Stresses: crust and lithosphere, VOLCANOLOGY, Research Article, geophysics, subduction, intraslab, seismicity
Sponsorship
Royal Society (URF\R1\180088)
UKRI | Natural Environment Research Council (NERC) (COMET)
Identifiers
jgrb55502, 2021jb023658
External DOI: https://doi.org/10.1029/2021jb023658
This record's URL: https://www.repository.cam.ac.uk/handle/1810/334695
Rights
Licence:
http://creativecommons.org/licenses/by/4.0/
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