کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4677372 1634795 2012 10 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
An unsually large ULVZ at the base of the mantle near Hawaii
کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات علوم زمین و سیاره ای (عمومی)
پیش نمایش صفحه اول مقاله
An unsually large ULVZ at the base of the mantle near Hawaii
چکیده انگلیسی

Previous studies have documented the presence of ultra-low-velocity-zones (ULVZs) at the base of the mantle, through observations of body wave complexities. Geometrically their heights are in the range of ∼5–30km, while little is known about their lateral extent beyond about 102 km, due to limitations in sampling. Here we show remarkable features in the waveforms of S/Sdiff phases of western Pacific events observed at stations in North America that indicate the presence of a very large ultra-low-velocity-zone (ULVZ) at the base of the mantle, centered ∼11°∼11° to the southwest of Hawaii, within and near the northern border of the Pacific LLSVP. Waveform complexities include strongly delayed (>30s) postcursors. Measurements of travel times, beamforming analysis of out-of-plane energy, and full waveform comparisons with 3D numerical simulations, constrain the location, lateral extent, height and velocity reduction of the ULVZ with some level of trade-off. The simplified 3D model consists of a cylindrical ULVZ with a large aspect ratio of ∼20km in height and ∼910km in diameter at the CMB. The shear wave velocity reduction is ∼20%∼20%. This is to our knowledge the largest ULVZ mapped to date and the first time the lateral extent of a ULVZ has been constrained with some precision. Its location suggests that it may be the root of a long-lived, stable plume responsible for the Hawaiian volcanic chain, the hotspot track with the largest buoyancy flux.


► Waveform complexities in core-diffracted phases across the Pacific reveal a ULVZ.
► Complexities include postcursors delayed >30s in the 10–30 s period band.
► Data analysis and 3D waveform modeling constrain the geometry and strength of the zone.
► Its aspect ratio is ∼1000km in width and ∼20km in height.
► The final model is located SW of, and might be related to the Hawaiian hotspot.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Earth and Planetary Science Letters - Volumes 355–356, 15 November 2012, Pages 213–222
نویسندگان
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