Earth's Solid Inner Core: Seismic Implications of Freezing and Melting  

作　　者：Vernon F Cormier Januka Attanayake 

机构地区：[1]Department of Physics, University of Connecticut [2]Center for Integrative Geoscience,University of Connecticut [3]Center for Integrative Geoscience, University of Connecticut

出　　处：《Journal of Earth Science》2013年第5期683-698,共16页地球科学学刊（英文版）

基　　金：supported by the National Science Foundation of USA(Nos.EAR 07-38492 and EAR 11-60917)

摘　　要：Seismic P velocity structure is determined for the upper 500 km of the inner core and lowermost 200 km of the outer core from differential travel times and amplitude ratios. Results confirm the existence of a globally uniform F region of reduced P velocity gradient in the lowermost outer core, consistent with iron enrichment near the boundary of a solidifying inner core. P velocity of the inner core between the longitudes 45~E and 180~E （quasi-Eastern Hemisphere） is greater than or equal to that of an AK135-F reference model whereas that between 180~W and 45~E （quasi-Western Hemisphere） is less than that of the reference model Observation of this heterogeneity to a depth of 550 km below the inner core and the existence of transitions rather than sharp boundaries between quasi-hemispheres favor either no or very slow inner core super rotation or oscillations with respect to the mantle. Degree- one seismic heterogeneity may be best explained by active inner core freezing beneath the equatorial Indian Ocean dominating structure in the quasi-Eastern Hemisphere and inner core melting beneath equatorial Pacific dominating structure in the quasi-Western Hemisphere. Variations in waveforms also suRgest the existence of smaller-scale （1 to 100 km） heterogeneity.Seismic P velocity structure is determined for the upper 500 km of the inner core and lowermost 200 km of the outer core from differential travel times and amplitude ratios. Results confirm the existence of a globally uniform F region of reduced P velocity gradient in the lowermost outer core, consistent with iron enrichment near the boundary of a solidifying inner core. P velocity of the inner core between the longitudes 45~E and 180~E （quasi-Eastern Hemisphere） is greater than or equal to that of an AK135-F reference model whereas that between 180~W and 45~E （quasi-Western Hemisphere） is less than that of the reference model Observation of this heterogeneity to a depth of 550 km below the inner core and the existence of transitions rather than sharp boundaries between quasi-hemispheres favor either no or very slow inner core super rotation or oscillations with respect to the mantle. Degree- one seismic heterogeneity may be best explained by active inner core freezing beneath the equatorial Indian Ocean dominating structure in the quasi-Eastern Hemisphere and inner core melting beneath equatorial Pacific dominating structure in the quasi-Western Hemisphere. Variations in waveforms also suRgest the existence of smaller-scale （1 to 100 km） heterogeneity.

关 键 词：Earth＇s inner core seismic structure geodynamo. 

分 类 号：P31[天文地球—固体地球物理学]