Temporal Changes of the Inner Core From Globally Distributed Repeating Earthquakes

2020 ◽  
Vol 125 (3) ◽  
Author(s):  
Yi Yang ◽  
Xiaodong Song
Keyword(s):  
Inner Core ◽  
Temporal Changes ◽  
Repeating Earthquakes ◽  
Globally Distributed

An Evaluation of the Timing Accuracy of Global and Regional Seismic Stations and Networks

2021 ◽  
Author(s):  
Yi Yang ◽  
Xiaodong Song ◽  
Adam T. Ringler
Keyword(s):  
Inner Core ◽  
Seismic Station ◽  
Temporal Changes ◽  
Time Range ◽  
Timing Accuracy ◽  
Seismic Stations ◽  
Arrival Times ◽  
Timing Errors ◽  
Repeating Earthquakes ◽  
Core Boundary

Abstract Clock accuracy is a basic parameter of any seismic station and has become increasingly important for seismology as the community seeks to refine structures and dynamic processes of the Earth. In this study, we measure the arrival time differences of moderate repeating earthquakes with magnitude 5.0–5.9 in the time range of 1991–2017 at the same seismic stations by cross-correlating their highly similar waveforms and thereby identify potential timing errors from the outliers of the measurements. The method has very high precision of about 10 ms and shows great potential to be used for routine inspection of the timing accuracy of historical and future digital seismic data. Here, we report 5131 probable cases of timing errors from 451 global and regional stations available from the Incorporated Research Institutions for Seismology Data Management Center, ranging from several tens of milliseconds to over 10 s. Clock accuracy seems to be a prevailing problem in permanent stations with long-running histories. Although most of the timing errors have already been tagged with low timing quality, there are quite a few exceptions, which call for greater attention from network operators and the seismological community. In addition, seismic studies, especially those on temporal changes of the Earth’s media from absolute arrival times, should be careful to avoid misinterpreting timing errors as temporal changes, which is indeed a problem in some previous studies of the Earth’s inner core boundary.

Comment on “Origin of temporal changes of inner-core seismic waves” by Yang and Song (2020)

2021 ◽  
Vol 553 ◽  
pp. 116640 ◽  
Author(s):  
Jiayuan Yao ◽  
Dongdong Tian ◽  
Li Sun ◽  
Lianxing Wen
Keyword(s):  
Seismic Waves ◽  
Inner Core ◽  
Temporal Changes

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

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>

An Electron Microscopic Study of an Avian Reovirus that Causes Arthritis

1971 ◽  
Vol 29 ◽  
pp. 254-255
Author(s):  
E, R. Walker ◽  
N. O. Olson ◽  
M. H. Friedman
Keyword(s):  
Electron Microscopy ◽  
Viral Genome ◽  
Inner Core ◽  
Avian Reovirus ◽  
Electron Microscopic ◽  
Outer Coat ◽  
Acid Type ◽  
Chicken Eggs ◽  
Icosahedral Particle ◽  
Mature Virus

An unidentified virus, responsible for an arthritic-like condition in chickens was studied by electron microscopy and other methods of viral investigation. It was characterized in chorio-allantoic membrane (CAM) lesions of embryonating chicken eggs and in tissue culture as to: 1) particle size; 2) structure; 3) mode of replication in the cell; and 4) nucleic acid type.The inoculated virus, coated and uncoated, is first seen in lysosomal-like inclusions near the nucleus; the virions appear to be uncoated in these electron dense inclusions (Figure 1), Although transfer of the viral genome from these inclusions is not observable, replicating virus and mature virus crystals are seen in the cytoplasm subsequent to the uncoating of the virions.The crystals are formed in association with a mass of fibrils 50 to 80 angstroms in diameter and a ribosome-studded structure that appears to be granular endoplasmic reticulum adapted to virus replication (Figure 2). The mature virion (Figure 3) is an icosahedral particle approximately 75 millimicrons in diameter. The inner core is 45 millimicrons, the outer coat 15 millimicrons, and the virion has no envelope.

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