Basal Accretion Along the South Central Chilean Margin and Its Relationship to Great Earthquakes

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dc.citation.articleNumbere2020JB019861
dc.citation.issueNumber11
dc.citation.journalTitleJournal of Geophysical Research: Solid Earth
dc.citation.volumeNumber125
dc.contributor.authorBangs, N.L.
dc.contributor.authorMorgan, J.K.
dc.contributor.authorTréhu, A.M.
dc.contributor.authorContreras‐Reyes, E.
dc.contributor.authorArnulf, A.F.
dc.contributor.authorHan, S.
dc.contributor.authorOlsen, K.M.
dc.contributor.authorZhang, E.
dc.date.accessioned2020-12-16T22:09:03Z
dc.date.available2020-12-16T22:09:03Z
dc.date.issued2020
dc.description.abstractThe south central Chilean margin regularly produces many of the world's largest earthquakes and tsunami, including the 2010 Mw 8.8 Maule and 1960 Mw 9.5 Valdivia events. In 2017, we acquired seismic reflection data along ~1,000 km of the margin using the R/V Langseth's 15 km long receiver array and 108.2 l (6,600 in3) seismic source to image structures associated with these ruptures. We focus on the Valdivia segment with the largest coseismic slip (~40 m). The outer 40 km of the forearc is an accretionary wedge constructed primarily of stacked sedimentary packages with irregular lengths and thicknesses and little along‐strike continuity. Forearc structures indicate that the accretionary wedge grows primarily through basal accretion of the downgoing trench fill. The décollement propagates along a weak boundary near the top of the trench fill but occasionally branches downward into the underthrust sediment along bedding horizons, peeling off slices that are underplated to the forearc. The shallow décollement level and the rarity of underplating events allow most of the trench sediment to subduct. As a result, only ~30% of the incoming sediment has been accreted since the Early Pliocene. This implies that, on average, ~1 km of sediment must subduct beyond the outer forearc, an inference that is supported by our seismic images. We propose that the thickness and great downdip and along‐strike extent of the underthrust layer, which separates the megathrust from the underlying roughness of the igneous ocean crust, ensures a smooth broad zone of strong coupling that generates the world's largest earthquakes and tsunami.
dc.identifier.citationBangs, N.L., Morgan, J.K., Tréhu, A.M., et al.. "Basal Accretion Along the South Central Chilean Margin and Its Relationship to Great Earthquakes." <i>Journal of Geophysical Research: Solid Earth,</i> 125, no. 11 (2020) Wiley: https://doi.org/10.1029/2020JB019861.
dc.identifier.doihttps://doi.org/10.1029/2020JB019861
dc.identifier.urihttps://hdl.handle.net/1911/109750
dc.language.isoeng
dc.publisherWiley
dc.rightsArticle is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
dc.titleBasal Accretion Along the South Central Chilean Margin and Its Relationship to Great Earthquakes
dc.typeJournal article
dc.type.dcmiText
dc.type.publicationpublisher version
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