Slow differential rotation of the Earth's inner core indicated by temporal changes in scattering

Nature ◽  
2000 ◽  
Vol 405 (6785) ◽  
pp. 445-448 ◽  
Author(s):  
John E. Vidale ◽  
Doug A. Dodge ◽  
Paul S. Earle
Keyword(s):  
Differential Rotation ◽  
Inner Core ◽  
Temporal Changes ◽  
Earth’S Inner Core

Seismological evidence for differential rotation of the Earth's inner core

Nature ◽  
1996 ◽  
Vol 382 (6588) ◽  
pp. 221-224 ◽  
Author(s):  
Xiaodong Song ◽  
Paul G. Richards
Keyword(s):  
Differential Rotation ◽  
Inner Core ◽  
Earth’S Inner Core

Viscous drag and the differential rotation of the Earth's core

1997 ◽  
Vol 57 (1) ◽  
pp. 231-233
Author(s):  
DAVID L. BOOK ◽  
J. A. VALDIVIA
Keyword(s):  
Simple Model ◽  
Differential Rotation ◽  
Dynamic Viscosity ◽  
Inner Core ◽  
Outer Core ◽  
Viscous Drag ◽  
Earth’S Rotation ◽  
The Core ◽  
The Earth ◽  
Earth’S Inner Core

It is proposed that the differential rotation of the Earth's inner core deduced by Song and Richards is due to a combination of the deceleration of the Earth's rotation and the viscous drag between the Earth's inner and outer cores. If this model is correct then the dynamic viscosity in the outer core of the Earth can be estimated to be μ≈104 poise. Besides providing a novel way of determining the viscosity of the core, this simple model suggests some new tests and shows how astronomical effects can influence geological phenomena.

Nature of inner-core temporal changes and a precise estimate of differential inner-core rotation rate

2021 ◽  
Author(s):  
Yi Yang ◽  
Xiaodong Song
Keyword(s):  
Differential Rotation ◽  
Rotation Rate ◽  
Inner Core ◽  
Temporal Changes ◽  
The Other ◽  
Lateral Velocity ◽  
High Quality ◽  
Other Hand ◽  
Core Rotation ◽  
Inner Core Rotation

<div> <p>Temporal changes of the inner core over several years have been well observed by different studies, especially those using high-quality repeating earthquakes (i.e., doublets). The phenomenon has commonly been interpreted as the differential rotation of the inner core shifting its interior heterogeneities. However, an alternative interpretation, the rapid growing or shrinking at the inner core boundary (ICB), is favored by some studies. On the other hand, estimates of the inner-core rotation rate vary by an order of magnitude.</p> <p>In this study, we used high-quality doublets from our previous systematic global search and analyzed the temporal changes (in terms of arrival times and waveforms) of inner core waves (both the refractive PKIKP and the reflective PKiKP) at the distance range between 128° and 142°. Using SKP (or PP) phase as a reference to eliminate possible clock errors, we found that the temporal changes are mostly from the PKIKP arrivals and always start before the onset of the late-arriving PKiKP. The observation is consistent with the proposal of differential rotation and rules out the ICB as the sole source of the temporal changes.</p> <p>On the other hand, we discovered compelling evidence of the differential rotation. Stations AAK and KZA in Kyrgyzstan are virtually the same distance to the doublets along the South Sandwich Islands (SSI) and hence are referred to as twin stations by us. The fortuitous geometry captures the underlying local structures, which have complex lateral velocity gradients. The yearly temporal change from different doublets also varies a lot, but surprisingly, it strongly correlates with the underlying velocity gradient, providing unequivocal evidence for the rotation of the inner core. The rotation rate could be accurately determined as 0.127° ± 0.006° per year at 95% confidence level in 1991-2010. In other words, when the lapse of a doublet is about 6.3 years, the inner core structure sampled by the earlier event to AAK is captured by its later repeater to KZA, which agrees very well with the real data.</p> <p>We believe that the above results largely resolve the debates on the origin of the temporal changes of the inner core and provide the most precise estimation of the differential rotation rate for the 1991-2010 time period.</p> </div>

Strong shear softening induced by superionic hydrogen in Earth's inner core

2021 ◽  
Vol 568 ◽  
pp. 117014
Author(s):  
Wenzhong Wang ◽  
Yunguo Li ◽  
John P. Brodholt ◽  
Lidunka Vočadlo ◽  
Michael J. Walter ◽  
...  
Keyword(s):  
Inner Core ◽  
Strong Shear ◽  
Earth’S Inner Core
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