Cascadia subduction tremor muted by crustal faults

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Deep, episodic slow slip on the Cascadia subduction megathrust of western North America is accompanied by low-frequency tremor in a zone of high fluid pressure between 30 and 40 km depth. Tremor density (tremor epicenters per square kilometer) varies along strike, and lower tremor density statistically correlates with upper plate faults that accommodate northward motion and rotation of forearc blocks. Upper plate earthquakes occur to 35 km depth beneath the faults. We suggest that the faults extend to the overpressured megathrust, where they provide fracture pathways for fluid escape into the upper plate. This locally reduces megathrust fluid pressure and tremor occurrence beneath the faults. Damping of tremor and related slow slip caused by fluid escape could affect fault properties of the megathrust, possibly influencing the behavior of great earthquakes.

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Publication type Article
Publication Subtype Journal Article
Title Cascadia subduction tremor muted by crustal faults
Series title Geology
DOI 10.1130/G38835.1
Volume 45
Issue 6
Year Published 2017
Language English
Publisher Geological Society of America
Contributing office(s) Geology, Minerals, Energy, and Geophysics Science Center
Description 4 p.
First page 515
Last page 518
Country Canada, United States
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