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TitleRole of serpentinized mantle wedge in affecting megathrust seismogenic behavior in the area of the 2010 M=8.8 Maule Earthquake
AuthorWang, KORCID logo; Huang, T; Tilmann, F; Peacock, S M; Lange, D
SourceGeophysical Research Letters vol. 47, issue 22, 2020 p. 1-10, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20200525
PublisherBlackwell Publishing Ltd.
Mediapaper; on-line; digital
File formatpdf; html
AreaMaule; Chile
Lat/Long WENS -75.0000 -71.3333 -33.1667 -35.0000
Subjectstectonics; igneous and metamorphic petrology; mineralogy; Science and Technology; Nature and Environment; Health and Safety; earthquakes; aftershocks; seismic risk; seismic velocities; tectonic setting; subduction zones; fault zones; mantle; thermal analyses; modelling; bedrock geology; lithology; serpentinites; antigorite; chrysotile; lizardite; 2010 M8.8 Maule Earthquake
Illustrationslocation maps; diagrams; schematic sections
ProgramPublic Safety Geoscience Assessing Earthquake Geohazards
Released2020 10 26
AbstractWhat controls subduction megathrust seismogenesis downdip of the mantle wedge corner (MWC)? We propose that, in the region of the 2010 Mw=8.8 Maule, Chile, earthquake, serpentine minerals derived from the base of the hydrated mantle wedge exert a dominant control. Based on modeling, we predict that the megathrust fault zone near the MWC contains abundant lizardite/chrysotile-rich serpentinite that transforms to antigorite-rich serpentinite at greater depths. From the MWC at 32-40 km depth to about 60 km, the predominantly velocity-strengthening megathrust accommodated dynamic propagation of the 2010 rupture but with small slip and negative stress drop. The downdip distribution of interplate aftershocks exhibits a gap around the MWC that can be explained by the velocity-strengthening behavior of lizardite/chrysotile. Interspersed velocity-weakening and dynamic weakening antigorite-rich patches farther downdip may be responsible for increased abundance of aftershocks and possibly for some of the high-frequency energy radiation during the 2010 rupture.
Summary(Plain Language Summary, not published)
A subduction megathrust rupture may extend from the trench to beneath populated coastal area. To understand what controls the megathrust seismogenic behavior of its deeper part, we conduct a case study of the 2010 magnitude 8.8 Maule, Chile, earthquake and its aftershocks. With numerical thermal modeling, we find that the deep seismogenic behavior may be controlled by serpentine materials derived from the base of the overlying hydrated mantle wedge. The deep part of the megathrust ruptured 'passively' against increasing resistance (negative stress drop). Lower-temperature serpentines lizardite and chrysotile that are known to facilitate aseismic slip may be responsible for an observed gap in aftershock distribution in the downdip direction. Higher-temperature serpentine antigorite that is known to facilitate seismic slip may be responsible for increased aftershocks farther downdip and possibly radiation of high-frequency energy during the 2010 Maule earthquake.

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