气候变化领域集成服务门户(CCPortal): Depth-Dependent Azimuthal Anisotropy Beneath the Juan de Fuca Plate System

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DOI	10.1029/2020JB019477
	Depth-Dependent Azimuthal Anisotropy Beneath the Juan de Fuca Plate System
	Eilon Z.C.; Forsyth D.W.
发表日期	2020
ISSN	21699313
卷号	125 期号:8
英文摘要	We use surface wave measurements to reveal anisotropy as a function of depth within the Juan de Fuca and Gorda plate system. Using a two-plane wave method, we measure phase velocity and azimuthal anisotropy of fundamental mode Rayleigh waves, solving for anisotropic shear velocity. These surface wave measurements are jointly inverted with constraints from SKS splitting studies using a Markov chain approach. We show that the two data sets are consistent and present inversions that offer new constraints on the vertical distribution of strain beneath the plates and the processes at spreading centers. Anisotropy of the Juan de Fuca plate interior is strongest (~2.4%) in the low-velocity zone between ~40- to 90-km depth, with ENE direction driven by relative shear between plate motion and mantle return flow from the Cascadia subduction zone. In disagreement with Pn measurements, weak (~1.1%) lithospheric anisotropy in Juan de Fuca is highly oblique to the expected ridge-perpendicular direction, perhaps connoting complex intralithospheric fabrics associated with melt or off-axis downwelling. In the Gorda microplate, strong shallow anisotropy (~1.9%) is consistent with Pn inversions and aligned with spreading and may be enhanced by edge-driven internal strain. Weak anisotropy with ambiguous orientation in the low-velocity zone can be explained by Gorda's youth and modest motion relative to the Pacific. Deeper (≥90 km) fabric appears controlled by regional flow fields modulated by the Farallon slab edge: anisotropy is strong (~1.8%) beneath Gorda, but absent beneath the Juan de Fuca, which is in the strain shadow of the slab. ©2020. American Geophysical Union. All Rights Reserved.
英文关键词	mantle fabric; oceanic asthenosphere; oceanic lithosphere; surface wave anisotropy
语种	英语
来源期刊	Journal of Geophysical Research: Solid Earth
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/187659
作者单位	Department of Earth Science, University of California Santa Barbara, Santa Barbara, CA, United States; Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI, United States
推荐引用方式 GB/T 7714	Eilon Z.C.,Forsyth D.W.. Depth-Dependent Azimuthal Anisotropy Beneath the Juan de Fuca Plate System[J],2020,125(8).
APA	Eilon Z.C.,&Forsyth D.W..(2020).Depth-Dependent Azimuthal Anisotropy Beneath the Juan de Fuca Plate System.Journal of Geophysical Research: Solid Earth,125(8).
MLA	Eilon Z.C.,et al."Depth-Dependent Azimuthal Anisotropy Beneath the Juan de Fuca Plate System".Journal of Geophysical Research: Solid Earth 125.8(2020).