Subduction megathrust heterogeneity characterized from 3D seismic data

Nature Geoscience
By: , and 

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Abstract

Megathrust roughness and structural complexity are thought to be controls on earthquake slip at subduction zones because they result in heterogeneity in shear strength and resolved stress. However, because active megathrust faults are difficult to observe, the causes and scales of complexity are largely unknown. Here we measured the in situ properties of the megathrust of the Middle America subduction zone in a three-dimensional seismic reflection volume to determine how fault properties vary. We quantify spatial variability in the megathrust roughness, overburden and rock physical properties. Heterogeneity in the megathrust roughness exists at length scales of a few kilometres because the megathrust is dissected by active lower-plate normal faults, which offset the megathrust and renewed fault roughness. Spatial variations in the rock physical properties at the plate interface are characterized by correlation length scales of hundreds of metres. Frontal prism taper, historical seismicity and the variation in earthquake stress drop values local to the megathrust are all affected by the heterogeneity at these length scales. Both geometric and rheological complexities may therefore control the mechanical behaviour of the subduction plate interface, which includes earthquake rupture characteristics.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Subduction megathrust heterogeneity characterized from 3D seismic data
Series title Nature Geoscience
DOI 10.1038/s41561-020-0562-9
Volume 13
Year Published 2020
Language English
Publisher Nature
Contributing office(s) Pacific Coastal and Marine Science Center
Description 6 p.
First page 369
Last page 374
Country Costa Rica
Other Geospatial Central America megathrust, Pacific Ocean
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