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Related Concept Videos

IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations01:08

IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations

Identical bonds within a polyatomic group can stretch symmetrically (in-phase) or asymmetrically (out-of-phase). Similar to hydrogen bonding, these vibrations also influence the shape of the IR peak. Generally, asymmetric stretching frequencies are higher than symmetric stretching frequencies. For example, primary amines exhibit two distinct IR peaks between 3300–3500 cm−1 corresponding to the symmetric and asymmetric N-H stretching, while secondary amines exhibit a single stretching vibration...
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Forced Oscillations01:06

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Shock Waves01:16

Shock Waves

While deriving the Doppler formula for the observed frequency of a sound wave, it is assumed that the speed of sound in the medium is greater than the source's speed through it. When this condition is breached, a shock wave occurs.
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Magnetic Resonance Derived Myocardial Strain Assessment Using Feature Tracking
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Published on: February 13, 2011

Inner core differential motion confirmed by earthquake waveform doublets.

Jian Zhang1, Xiaodong Song, Yingchun Li

  • 1Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA.

Science (New York, N.Y.)
|August 27, 2005
PubMed
Summary

Earth's inner core rotates faster than the mantle and crust. Analysis of seismic waves passing through the inner core confirms this rotation, estimated at 0.3 to 0.5 degrees per year.

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Area of Science:

  • Geophysics
  • Seismology
  • Earth Science

Background:

  • Earth's inner core properties are challenging to study.
  • Seismic waves traversing the inner core provide insights into its dynamics.

Purpose of the Study:

  • To analyze temporal changes in seismic wave travel times.
  • To confirm the rotation of Earth's inner core relative to the mantle and crust.

Main Methods:

  • Analysis of 18 high-quality waveform doublets from the South Sandwich Islands region.
  • Tracking seismic signals (PKP(DF)) that have passed through the inner core.
  • Utilizing data from 58 stations in and near Alaska to observe travel time variations.

Main Results:

  • Consistent temporal changes in seismic wave travel times were observed.
  • Dissimilarities in the PKP(DF) wave codas were noted.
  • The study confirmed Earth's inner core is rotating faster than the mantle and crust.

Conclusions:

  • Earth's inner core rotation is confirmed at approximately 0.3 to 0.5 degrees per year.
  • Waveform doublet analysis effectively mitigates issues from earthquake mislocations and small-scale heterogeneities.