کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
5787333 1641479 2016 22 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
On observation of local strong heterogeneity in the Earth's inner core below southeastern Asia
ترجمه فارسی عنوان
در مشاهده ناهمگونی قوی محلی در هسته داخلی زمین زیر جنوب شرقی آسیا
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات فیزیک زمین (ژئو فیزیک)
چکیده انگلیسی
The dimensions and nature of multi-scale structural heterogeneities in the Earth's inner core (IC) provide important constraints on its mineralogy and formation history. Teleseismic body waves with turn points close to the inner core boundary (ICB) provide a unique tool for imaging the fine structure of the upper IC. In this study, we invoke differential travel times and amplitudes of PKPBC and PKPDF waveforms observed in crossing polar and equatorial paths to provide more constraints on the heterogeneity previously located in the quasi-eastern hemisphere of the IC (Kaazik et al., 2015; Krasnoshchekov et al., 2016). A more refined analysis of quasi-polar PKPBC/PKPDF amplitude ratios measured within the heterogeneity indicates that seismic attenuation is both frequency and depth dependent, and its relatively low Q-factor at 1 Hz of approximately 118 tends to grow with depth. Outside the heterogeneity, no pronounced polar-equatorial differences are observed; the estimated Q factor is about twice as large and not directionally dependent. We also analyse new differential travel times of rays that enable sampling of the anomaly at greater depths. The analysis exhibits the polar - equatorial contrasts observed in the heterogeneity terminate at approximately 520 km below the ICB, which we interpret to be its bottom. The earlier interpretation of the heterogeneity in terms of strong anisotropic volume amidst the almost isotropic eastern hemisphere of the IC can be retained, and the lower bound of anisotropy strength within the anomaly is determined to be 2%.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Physics of the Earth and Planetary Interiors - Volume 261, Part B, December 2016, Pages 187-195
نویسندگان
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