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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.
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. Look for a ...
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.
In areas with limited seismograph or earthquake coverage, multiple phases of S waves can be used for tomographic models. These are of lower resolution than P wave models, due to the distances involved and fewer bounce-phase data available. S waves can also be used in conjunction with P waves for differential arrival time models.
Receiver functions use Snell's law refraction of P waves and converted S waves to estimate the depth of the Moho. They are only generated clearly if the central angle (angle subtended at the center of the Earth) between the seismic event and the seismograph station is between 30 and 95 degrees (between about 3300 and 8900 km separation). [4 ...
The sideways-shaking S waves (following the green lines) arrive some seconds later, traveling a little over half the speed of the P waves; the delay is a direct indication of the distance to the quake. S waves may take an hour to reach a point 1000 km away. Both of these are body-waves, that pass directly through the earth's crust.
The red line is the P-wave velocity, the blue line is the S-wave velocity, and the green line density. (Data was adopted from the RockHound Python library.) Seismic velocity structure is the distribution and variation of seismic wave speeds within Earth's and other planetary bodies' subsurface.
Due to mode conversion, a P-wave can reflect upwards as an S-wave (also known as a secondary, shear or transverse wave) when it hits an interface (e.g., solid-liquid). Other P-wave to S-wave (P-S) conversions can occur, but the down-up conversion is the primary focus. Unlike P-waves, converted shear waves are largely unaffected by fluids. [1]