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Impact of bending-related faulting and oceanic-plate topography on slab hydration and intermediate-depth seismicity br

Impact of bending-related faulting and oceanic-plate topography on slab hydration and intermediate-depth seismicity br
Impact of bending-related faulting and oceanic-plate topography on slab hydration and intermediate-depth seismicity br
It is commonly assumed that intermediate-depth seismicity is in some way linked to dehydration reactions inside subducting oceanic plates. Although there is growing evidence that the hydration state of an oceanic plate is controlled by its structure and degree of faulting, we do not have a quantitative understanding of this relationship. Double seismic zones offer the possibility of investigating changes in oceanic-plate hydration not only along strike but also with depth beneath the slab surface. To quantify the impact of oceanic-plate structure and faulting on slab hydration and intermediate-depth seismicity, with a focus on the genesis of double seismic zones, we correlate high-resolution earthquake catalogs and seafloor maps of ship-based bathymetry for the northern Chilean and Japan Trench subduction zones. The correlations show only a weak influence of oceanic-plate structure and faulting on seismicity on the upper plane of the double seismic zone, which may imply that hydration is limited by slow reaction kinetics at low temperatures 5–7 km below the seafloor and by the finite amount of exposed wall rock in the outer-rise region. These factors seem to limit hydration even if abundant water is available. Seismicity in the lower plane is, in contrast, substantially enhanced where deformation of the oceanic plate is high and distributed across intersecting faults. This likely leads to an increase in the volume of damaged wall rock around the faults, thereby promoting the circulation of water to mantle depths where serpentinization is faster due to elevated temperatures. Increased lower-plane seismicity around subducting oceanic features such as seamounts or fracture zones may also be caused by enhanced faulting around these features. Our results provide a possible explanation for the globally observed presence of rather homogeneous upper-plane seismicity in double seismic zones as well as for the commonly patchy and inhomogeneous distribution of lower-plane seismicity.
1553-040X
562-584
Geersen, Jacob
abcf5f76-3608-4322-ab54-7bfb8dfcaf2d
Sippl, Christian
6b2f4a1b-c2ab-4b91-a971-77957ba59862
Harmon, Nicholas
10d11a16-b8b0-4132-9354-652e72d8e830
Geersen, Jacob
abcf5f76-3608-4322-ab54-7bfb8dfcaf2d
Sippl, Christian
6b2f4a1b-c2ab-4b91-a971-77957ba59862
Harmon, Nicholas
10d11a16-b8b0-4132-9354-652e72d8e830

Geersen, Jacob, Sippl, Christian and Harmon, Nicholas (2022) Impact of bending-related faulting and oceanic-plate topography on slab hydration and intermediate-depth seismicity br. Geosphere, 18 (2), 562-584. (doi:10.1130/GES02367.1).

Record type: Article

Abstract

It is commonly assumed that intermediate-depth seismicity is in some way linked to dehydration reactions inside subducting oceanic plates. Although there is growing evidence that the hydration state of an oceanic plate is controlled by its structure and degree of faulting, we do not have a quantitative understanding of this relationship. Double seismic zones offer the possibility of investigating changes in oceanic-plate hydration not only along strike but also with depth beneath the slab surface. To quantify the impact of oceanic-plate structure and faulting on slab hydration and intermediate-depth seismicity, with a focus on the genesis of double seismic zones, we correlate high-resolution earthquake catalogs and seafloor maps of ship-based bathymetry for the northern Chilean and Japan Trench subduction zones. The correlations show only a weak influence of oceanic-plate structure and faulting on seismicity on the upper plane of the double seismic zone, which may imply that hydration is limited by slow reaction kinetics at low temperatures 5–7 km below the seafloor and by the finite amount of exposed wall rock in the outer-rise region. These factors seem to limit hydration even if abundant water is available. Seismicity in the lower plane is, in contrast, substantially enhanced where deformation of the oceanic plate is high and distributed across intersecting faults. This likely leads to an increase in the volume of damaged wall rock around the faults, thereby promoting the circulation of water to mantle depths where serpentinization is faster due to elevated temperatures. Increased lower-plane seismicity around subducting oceanic features such as seamounts or fracture zones may also be caused by enhanced faulting around these features. Our results provide a possible explanation for the globally observed presence of rather homogeneous upper-plane seismicity in double seismic zones as well as for the commonly patchy and inhomogeneous distribution of lower-plane seismicity.

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e-pub ahead of print date: 17 February 2022

Identifiers

Local EPrints ID: 456900
URI: http://eprints.soton.ac.uk/id/eprint/456900
ISSN: 1553-040X
PURE UUID: 655a41e2-21e3-4d8c-97b6-6a13a517fb1a
ORCID for Nicholas Harmon: ORCID iD orcid.org/0000-0002-0731-768X

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Date deposited: 16 May 2022 16:41
Last modified: 21 May 2022 01:39

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Author: Jacob Geersen
Author: Christian Sippl
Author: Nicholas Harmon ORCID iD

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