P wave
Part of a series on |
Earthquakes |
---|
A P wave (primary wave or pressure wave) is one of the two main types of elastic
Nomenclature
The name P wave can stand for either pressure wave (as it is formed from alternating
Seismic waves in the Earth
Primary and secondary waves are body waves that travel within the Earth. The motion and behavior of both P and S waves in the Earth are monitored to probe the interior
P-wave shadow zone
Almost all the information available on the structure of the Earth's deep interior is derived from observations of the travel times,
As an earthquake warning
Advance earthquake warning is possible by detecting the nondestructive primary waves that travel more quickly through the Earth's crust than do the destructive secondary and Rayleigh waves.
The amount of warning depends on the delay between the arrival of the P wave and other destructive waves, generally on the order of seconds up to about 60 to 90 seconds for deep, distant, large quakes such as the
Propagation
Velocity
In
In typical situations in the interior of the Earth, the density ρ usually varies much less than K or μ, so the velocity is mostly "controlled" by these two parameters.
The
Typical values for P wave velocity in earthquakes are in the range 5 to 8 km/s. The precise speed varies according to the region of the Earth's interior, from less than 6 km/s in the Earth's crust to 13.5 km/s in the lower mantle, and 11 km/s through the inner core.[6]
Rock Type | Velocity [m/s] | Velocity [ft/s] |
---|---|---|
Unconsolidated Sandstone | 4,600–5,200 | 15,000–17,000 |
Consolidated Sandstone | 5,800 | 19,000 |
Shale | 1,800–4,900 | 6,000–16,000 |
Limestone | 5,800–6,400 | 19,000–21,000 |
Dolomite | 6,400–7,300 | 21,000–24,000 |
Anhydrite | 6,100 | 20,000 |
Granite | 5,800–6,100 | 19,000–20,000 |
Gabbro | 7,200 | 23,600 |
Geologist Francis Birch discovered a relationship between the velocity of P waves and the density of the material the waves are traveling in:
See also
- Earthquake warning system
- Lamb waves
- Love wave
- S wave
- Surface wave
References
- ISBN 978-0-470-84347-5. Retrieved 2010-02-25.
- S2CID 4304379.
- ^
Rubinstein, Justin L.; Shelly, D. R.; Ellsworth, W. L. (2009). "Non-volcanic tremor: A window into the roots of fault zones". In Cloetingh, S.; Negendank, Jorg (eds.). New Frontiers in Integrated Solid Earth Sciences. Springer. p. 287 ff. ISBN 978-90-481-2736-8.
The analysis of seismic waves provides a direct high-resolution means for studying the internal structure of the Earth...
- ^
Fowler, C. M. R. (2005). "§4.1 Waves through the Earth". The solid earth: an introduction to global geophysics (2nd ed.). Cambridge University Press. p. 100. ISBN 978-0-521-58409-8.
Seismology is the study of the passage of elastic waves through the Earth. It is arguably the most powerful method available for studying the structure of the interior of the Earth, especially the crust and mantle.
- ^ Lowrie, William. The Fundamentals of Geophysics. Cambridge University Press, 1997, p. 149.
- ^ Dziewonski, Adam M.; Anderson, Don L. (1981). "Preliminary reference Earth model". Physics of the Earth and Planetary Interiors. 25 (4): 297–356. .
- ^
"Acoustic Logging". Geophysics. U.S. Environmental Protection Agency. 2011-12-12. Retrieved 2015-02-03.
- "Photo Glossary of Earthquakes". U.S. Geological Survey". Archived from the original on February 27, 2009. Retrieved March 8, 2009.