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P wave and S wave from seismograph Velocity of seismic waves in Earth versus depth. [1] The negligible S-wave velocity in the outer core occurs because it is liquid, while in the solid inner core the S-wave velocity is non-zero. A seismic wave is a mechanical wave of acoustic energy that travels through the Earth or another planetary body.
A P wave (primary wave or pressure wave) is one of the two main types of elastic body waves, called seismic waves in seismology. P waves travel faster than other seismic waves and hence are the first signal from an earthquake to arrive at any affected location or at a seismograph. P waves may be transmitted through gases, liquids, or solids.
[18] [19] P-waves, which can move through all states of matter and provide data on a range of depths, change speed based on the material's properties, such as type, density, and temperature. [ 3 ] [ 1 ] S-waves, in contrast, are constrained to solids and reveal information about the Earth's rigidity and internal composition, including the ...
The P wave is the first wave that is bigger than the other waves (the microseisms). Because P waves are the fastest seismic waves, they will usually be the first ones that the seismograph records. The next set of seismic waves on the seismogram will be the S waves. These are usually bigger than the P waves, and have higher frequency.
An earthquake's seismic moment can be estimated in various ways, which are the bases of the M wb, M wr, M wc, M ww, M wp, M i, and M wpd scales, all subtypes of the generic M w scale. See Moment magnitude scale § Subtypes for details. Seismic moment is considered the most objective measure of an earthquake's "size" in regard of total energy. [50]
(cm/s 2,gal) Ground Speed (cm/s) What People Feel Effects Indoors Effects Outdoors; 0 Undetectable (無感) below 0.8 gal Imperceptible to humans 1 Slight (微震) 0.8-2.5 gal People may feel slight shaking when motionless 2 Weak (輕震) 2.5-8.0 gal Most people will feel shaking, and some sleepers may wake up
Travel time in seismology means time for the seismic waves to travel from the focus of an earthquake through the crust to a certain seismograph station. [1] Travel-time curve is a graph showing the relationship between the distance from the epicenter to the observation point and the travel time.
Where an earthquake is not recorded on seismographs an isoseismal map showing the intensities felt at different areas can be used to estimate the location and magnitude of the quake. [1] Such maps are also useful for estimating the shaking intensity, and thereby the likely level of damage, to be expected from a future earthquake of similar ...