भूकंपदर्शी इसके अंग्रेजी अर्थ का उदाहरण

Information about Earth's core mostly comes from analysis of seismic waves and Earth's magnetic field.

She observed that the seismic waves reflect off the boundary of the inner core and can be detected by sensitive seismographs on the Earth's surface.

Almost all direct measurements that scientists have about the physical properties of the inner core are the seismic waves that pass through it.

On the basis of the seismic data, the inner core is estimated to be about 1221"nbsp;km in radius (2442"nbsp;km in diameter);, which is about 19% of the radius of the Earth and 70% of the radius of the Moon.

Although seismic waves propagate through the core as if it was solid, the measurements cannot distinguish between a perfectly solid material from an extremely viscous one.

That could be an explanation for the anisotropy detected in seismic studies.

Laboratory experiments and analysis of seismic wave velocities seem to indicate that the inner core consists specifically of ε-iron, a crystalline form of the metal with the hexagonal close-packed (hcp) structure.

This P-wave speed anisotropy has been confirmed by later studies, including more seismic data and study of the free oscillations of the whole Earth.

A preference for the crystals in the core to align in the north–south direction could account for the observed seismic anomaly.

Hamaguchi claimed, on the basis of seismic data, that the anisotropy of the inner core material, while oriented N-S, was more pronounced in "eastern" hemisphere of the inner core (at about 110 °E longitude, roughly under Borneo) than in the "western" hemisphere (at about 70 °W, roughly under Colombia).

In the 1990s, seismologists made various claims about detecting this kind of super-rotation by observing changes in the characteristics of seismic waves passing through the inner core over several decades, using the aforementioned property that it transmits waves more quickly in some directions.

Zhang compared recordings of "seismic doublets" (recordings by the same station of earthquakes occurring in the same location on the opposite side of the Earth, years apart), and revised that estimate to 0.

Specifically, fiber Bragg gratings are finding uses in instrumentation applications such as seismology, pressure sensors for extremely harsh environments, and as downhole sensors in oil and gas wells for measurement of the effects of external pressure, temperature, seismic vibrations and inline flow measurement.