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Seismic velocity structures and detailed features of the D”discontinuity near the core-mantle boundary beneath eastern Eurasia

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Seismic velocity structures and detailed features of the D”...

Geographic boundary and shear wave velocity structure of the“Pacific anomaly”near the core-mantle boundary beneath western Pacific

中国科学院地质与地球物理研究所第11届（2011年度）...

作者： Yumei He~(a,b,*),Lianxing Wen~(b,c) a Key Laboratory of the Earth’s Deep Interior,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,PR China b Department of Ceosciences,State University of New York at Stony Brook,Stony Brook,NY 11790,USA c School of Earth and Space Sciences,University of Science and Technology of China,Hefei,Anhui 230026,PR China

Shear and compressional velocity structures and features of the D" discontinuity near the core-mantle boundary(CMB) beneath eastern Eurasia are studied based on forward waveform modeling and differential -travel-time analysis of ScSH-SH,sScS-sS,PcP-P and pPcP-pP ***-quality differential-travel-time analysis reveals two high-velocity patches spanning a width of 3000 km and separated by a 300-km wide normal velocity *** maximum shear and compressional velocity perturbations reach 3.8%and 2.7%,*** data indicate that the D" discontinuity emerges in the high velocity patches and disappears in the normal-velocity ***,the features of the D" discontinuity,although constrained by rather sparse seismic data,vary from diffusive discontinuities in the eastern patch to sharp discontinuities in the western *** D" discontinuities occur at about 270 km above the CMB in the eastern patch with a shear velocity jump of 3.0-5.0%and a transitional depth of at least 100 km,and at 250 km above the CMB in the western patch with an abrupt shear velocity jump of 5.0%.A diffusive P wave discontinuity is also observed in the eastern patch with the similar features of the S wave *** inferred features of the D" discontinuity can be explained by the post-perovskite transformation in the lower *** observations that the D" discontinuities occur only in the high-velocity patches may be due to the effect of the positive Clapeyron slope of the post-perovskite transition,and the varying transitional depths of the D" discontinuity in the high-velocity regions may be caused by the compositional effects on the post-perovskite transition in the presence of strong variations of composition within the high-velocity *** high-velocity patches geographically correlate with the subduction of the Pacific and Indian plates in the past 30-60 Ma,and the normal-velocity gap falls into the subduction gap between the Pacific and Indian plates

关键词： Seismic velocity structure core-mantle boundary D"discontinuity Eastern Eurasia

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Geographic boundary and shear wave velocity structure of the...

Investigation of the SA evolution by using the CHAOS-4 model over 1997–2013

中国科学院地质与地球物理研究所2006学术年会

作者： Yumei He~(a*),Lianxing Wen~b,Tianyu Zheng~a a Seismological Laboratory(SKL-LE),Institute of Geology and Geophysics,Chinese Academy of Sciences, Beijing 100029,PR China b Department of Geosciences,State University of New York at Stony Brook,Stony Brook,New York,USA

We determine the geographical boundary and shear-velocity structure of a very-low velocity province at the base of the Earth’s mantle beneath western Pacific(we term it the "Pacific anomaly") based on the waveform modeling and travel time analysis of ScSH-SH *** seismic data are from the China National Digital Seismographic Network,the F-net in Japan,the Global Seismographic Network and several PASSCAL *** observed ScS-SH differential travel-time residuals allow the northwestern geographic boundary of the anomaly to be clearly *** seismic data also suggest that the average shearvelocity reduction inside the anomaly reaches -5%in the lowermost 300km of the *** modeling of the seismic data sampling the edge of the anomaly suggests that the northwestern boundary is best characterized by a shear-velocity model with a velocity jump of about 2%at about 100-145km above the core-mantle boundary and a thin(30-km thick) basal layer with a shear wave velocity reduction of -13%.Stacked seismic data sampling the middle of the anomaly,however,show no evidence for any internal discontinuity with a velocity decrease greater than -2%in the middle of the anomaly. Overall,the seismic data sampling the base of the "Pacific anomaly" can be explained by a negative shear-velocity gradient from 0%to -1%(top) to -13%(bottom) in the lowermost 220 km of the mantle,similar to those of a very-low velocity province beneath the South Atlantic Ocean and the Indian *** a strong negative shear-velocity gradient can be explained by partial melting of a compositional anomaly produced early in the Earth’s history located within a bottom thermal boundary *** travel time data also exhibit small-scale variations inside the anomaly,indicating existence of internal small-scale seismic heterogeneities inside the "Pacific anomaly".

关键词： shear wave velocity structure core-mantle boundary Pacific anomaly

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Science China Earth Sciences 2016年第5期59卷 1041-1050页

作者： OU JiaMing DU AiMin XU WenYao Key Laboratory of Earth and Planetary Physics Chinese Academy of Sciences Institute of Geology and Geophysics Chinese Academy of Sciences

The temporal and spatial evolution characteristics of the geomagnetic secular acceleration(SA) are investigated, based on CHAOS-4 core field model during the period of 1997–2013. The SA evolution on a short time scale is associated with the phenomenon of the geomagnetic jerk. More details of the global extent and the occurrence time of the successive jerks(the 1999, 2003, 2007, and 2011 jerks) are obtained. The location, size and reversed polarity pattern for the 1999 jerk are similar to those for the 2003 jerk in the Asian-Indian sector. While the 2007 and 2011 jerks mainly take place in the Atlantic sector. The direction and speed of the shift for the four jerks are different, identified by the occurrence time of the jerks. The zonal motions of the SA patches exhibit an oscillation pattern in the Asian-Indian sector, whereas a purely westward drifting pattern is along the equator in the Atlantic sector. It is believed that the shift of the jerks is related to the motion of SA-B_r patches observed at the core-mantle boundary(CMB).

关键词： Geomagnetic secular acceleration Geomagnetic jerk core-mantle boundary Zonal oscillation

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Deep mantle hydrogen in the pyrite-type FeO_(2)–FeO_(2)H system

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Geoscience Frontiers 2021年第2期12卷 975-981页

作者： Qingyang Hu Jin Liu Center for High Pressure Science and Technology Advanced Research(HPSTAR) Beijing100094China

The pyrite-type FeO_(2)and FeO_(2)H were synthesized at the pressure-temperature conditions relevant to Earth’s deep lower *** the water-iron reaction,the pyrite-phase is a good candidate to explain the chemical heterogeneities and seismological anomalies at the bottom of the *** solid solution of pyrite-type FeO_(2)and FeO_(2)H,namely the FeO_(2)Hx(0≤x≤1),is particularly interesting and introduces puzzling chemical states for both the O and H atoms in the deep *** the role of H in the FeO_(2)–FeO_(2)H system has been primarily investigated,discrepancies *** this work,we summarize recent progress on the pyrite-phase,including FeO_(2),FeO_(2)H,and FeO_(2)Hx,which is critical for understanding the water cycling,redox equilibria,and compositional heterogenicities in the deep lower mantle.

关键词： Deep lower mantle core-mantle boundary Pyrite-type phase Hydrogen-bearing phase

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Morphology and possible origins of the Perm anomaly in the lowermost mantle of Earth

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Earth and Planetary Physics 2021年第1期5卷 105-116页

作者： YuMei He LianXing Wen Yann Capdeville Key Laboratory of Earth and Planetary Physics Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China Mohe Observatory of Geophysics Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China Laboratory of Seismology and Physics of Earth’s Interior School of Earth and Space SciencesUniversity of Science and Technology of ChinaHefei 230026China Department of Geosciences State University of New York at Stony BrookStony BrookNew YorkUSA Laboratoire de Planétologie et Géodynamique de Nantes UMR6112CNRSUniversitéde NantesNantesFrance

We have constrained a small-scale,dome-shaped low-velocity structure near the core-mantle boundary(CMB)of Earth beneath Perm(the Perm anomaly)using travel-time analysis and three-dimensional(3-D)forward waveform modeling of seismic data sampling of the *** best-fitting dome-shaped model centers at 60.0°E,50.5°N,and has a height of 400 km and a radius that increases from 200 km at the top to 450 km at the *** velocity reduction varies from 0%at the top to–3.0%at 240km above the CMB to–3.5%at the CMB.A surrounding 240-km-thick high-velocity D''structure has also been *** Perm anomaly may represent a stable smallscale chemical pile in the lowermost mantle,although the hypothesis of a developing mantle plume cannot be ruled out.

关键词： seismic velocity structure core-mantle boundary Perm anomaly chemical pile

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REVERSED POLARITY PATCHS AT THE CMBAND GEOMAGNETIC FIELD REVERSAL

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REVERSED POLARITY PATCHS AT THE CMBAND GEOMAGNETIC FIELD REV...