Imperial College London
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DrRebeccaBell

Faculty of Engineering, Department of Earth Science & Engineering

Reader in Tectonics
 
 
 
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Contact

 

+44 (0)20 7594 0903rebecca.bell

 
 
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Location

 

2.37aRoyal School of MinesSouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@article{Morgan:2022:10.1016/j.epsl.2022.117651,
author = {Morgan, JK and Solomon, EA and Fagereng, A and Savage, HM and Wang, M and Meneghini, F and Barnes, PM and Bell, RE and French, ME and Bangs, NL and Kitajima, H and Saffer, DM and Wallace, LM},
doi = {10.1016/j.epsl.2022.117651},
journal = {Earth and Planetary Science Letters},
pages = {1--13},
title = {Seafloor overthrusting causes ductile fault deformation and fault sealing along the Northern Hikurangi Margin},
url = {http://dx.doi.org/10.1016/j.epsl.2022.117651},
volume = {593},
year = {2022}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - IODP Site U1518, drilled during IODP Expeditions 372 and 375, penetrated a large-offset (∼6 km) thrust, the Ppaku fault, rising from a megathrust that hosts recurring slow slip events along the Hikurangi margin. Although drilling intersected the fault zone at only ∼300 m below the seafloor within porous silty mudstone, it exhibits intense tectonic ductile deformation, including finely banded mudstones contorted into decimeter-scale folds; elongate mudstone clasts with grain tail complexes; stacked and truncated silt beds in distorted mudstones; and soft sediment injections. Locally, these ductile features are overprinted by brittle deformation, including normal faults, fracture arrays, and breccias. The more consolidated hanging wall is dominated by brittle structures, whereas the footwall exhibits ductile and brittle deformation that decreases in intensity with depth. The intense tectonic ductile deformation and asymmetric distribution of structures across the fault zone at Site U1518 can be explained by seafloor overthrusting. The emplacement of the hanging wall upon the footwall flat overrode high-porosity, undeformed, and previously unburied sediments, localizing shear deformation within these weak sediments. In contrast, the overconsolidated hanging wall preferentially experienced brittle deformation during folding and displacement. Interstitial pore water geochemical profiles at Site U1518 show a repetition of near-seafloor diagenetic sequences below the fault, consistent with overthrusting of previously unburied strata. The preserved diagenetic profiles in the footwall suggest that overthrusting occurred within the last 50-100 kyr, and indicate little along- or across-fault fluid flow at the location of Site U1518. Thus the Ppaku fault appears to define a low-permeability seal that restricts footwall consolidation, maintaining locally high pore fluid pressures and low fault strength. If similar low permeability structures occur elsewhere along the m
AU  - Morgan,JK
AU  - Solomon,EA
AU  - Fagereng,A
AU  - Savage,HM
AU  - Wang,M
AU  - Meneghini,F
AU  - Barnes,PM
AU  - Bell,RE
AU  - French,ME
AU  - Bangs,NL
AU  - Kitajima,H
AU  - Saffer,DM
AU  - Wallace,LM
DO  - 10.1016/j.epsl.2022.117651
EP  - 13
PY  - 2022///
SN  - 0012-821X
SP  - 1
TI  - Seafloor overthrusting causes ductile fault deformation and fault sealing along the Northern Hikurangi Margin
T2  - Earth and Planetary Science Letters
UR  - http://dx.doi.org/10.1016/j.epsl.2022.117651
UR  - http://hdl.handle.net/10044/1/98471
VL  - 593
ER  -
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