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Great (≥Mw8.0) megathrust earthquakes and the subduction of excess sediment and bathymetrically smooth seafloor

Scholl, David W ; Kirby, Stephen H ; von Huene, Roland ; Ryan, Holly ; Wells, Ray E ; Geist, Eric L

Geosphere (Boulder, Colo.), 2015-04, Vol.Pre-Issue Publication (2), p.236-265 [Periódico revisado por pares]

Geological Society of America

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  • Título:
    Great (≥Mw8.0) megathrust earthquakes and the subduction of excess sediment and bathymetrically smooth seafloor
  • Autor: Scholl, David W ; Kirby, Stephen H ; von Huene, Roland ; Ryan, Holly ; Wells, Ray E ; Geist, Eric L
  • Assuntos: Earthquakes ; Erosion ; global ; great earthquakes ; Joining ; Marine ; marine sediments ; megathrust earthquakes ; plate tectonics ; Rupture ; Sea beds ; Sediments ; Seismic phenomena ; Seismology ; subduction ; subduction zones ; thickness ; thrust sheets ; Trenches
  • É parte de: Geosphere (Boulder, Colo.), 2015-04, Vol.Pre-Issue Publication (2), p.236-265
  • Notas: ObjectType-Article-1
    SourceType-Scholarly Journals-1
    ObjectType-Feature-2
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  • Descrição: Using older and in part flawed data, Ruff (1989) suggested that thick sediment entering the subduction zone (SZ) smooths and strengthens the trench-parallel distribution of interplate coupling. This circumstance was conjectured to favor rupture continuation and the generation of high-magnitude (≥Mw8.0) interplate thrust (IPT) earthquakes. Using larger and more accurate compilations of sediment thickness and instrumental (1899 to January 2013) and pre-instrumental era (1700-1898) IPTs (n=176 and 12, respectively), we tested if a compelling relation existed between where IPT earthquakes ≥Mw7.5 occurred and where thick (≥1.0 km) versus thin (≤1.0 km) sedimentary sections entered the SZ. Based on the new compilations, a statistically supported statement (see Summary and Conclusions) can be made that high-magnitude earthquakes are most prone to nucleate at well-sedimented SZs. For example, despite the 7500 km shorter global length of thick-sediment trenches, they account for ∼53% of instrumental era IPTs ≥Mw8.0, ∼75% ≥Mw8.5, and 100% ≥Mw9.1. No megathrusts >Mw9.0 ruptured at thin-sediment trenches, whereas three occurred at thick-sediment trenches (1960 Chile Mw9.5, 1964 Alaska Mw9.2, and 2004 Sumatra Mw9.2). However, large Mw8.0-9.0 IPTs commonly (n=23) nucleated at thin-sediment trenches. These earthquakes are associated with the subduction of low-relief ocean floor and where the debris of subduction erosion thickens the plate-separating subduction channel. The combination of low bathymetric relief and subduction erosion is inferred to also produce a smooth trench-parallel distribution of coupling posited to favor the characteristic lengthy rupturing of high-magnitude IPT earthquakes. In these areas subduction of a weak sedimentary sequence further enables rupture continuation.
  • Editor: Geological Society of America
  • Idioma: Inglês
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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