66, 16–24 (1967).īath, M., Observations of Teleseismic Pn Phases, Pure and Appl. 64, 19–30 (1966).īath, M., An Earthquake with Exceptionally Strong Higher-mode Surface Waves, Pure and Appl. (1962).īath, M., Propagation of Sn and Pn to Teleseismic Distances, Pure and Appl. 41, 91–100 (1958).īath, M, M., Channel Waves in the Earth’s Continental Crust, Scientia 56, 8 pp. Runcorn, Ed.), Interscience, 2, 123–204 (1966).īath, M., An Investigation of the Uppsala Microseisms ( Almqvist & Wiksell, Uppsala 1949 ), 168 pp.īath, M., Comparison of Microseisms in Greenland, Iceland, and Scandinavia, Tellus 5, 109–134 (1953).īath, M., A Study of T Phases Recorded at the Kiruna Seismograph Station, Tellus 6, 63–72 (1954).īath, M., Ultra-long-period Motions from the Alaska Earthquake of July 10, 1958, Geofis. F., Fourier Methods in Geophysics, Methods and Techniques in Geophysics (S. This process is experimental and the keywords may be updated as the learning algorithm improves.Īnsell, J H, Observation of the Frequency-Dependent Amplitude Variation with Distance of P waves from 87° to 119°, Pure and Appl. These keywords were added by machine and not by the authors. Stoneley waves, which are related to Rayleigh waves, but follow a discontinuity surface in the earth’s interior Ĭhannel waves, which propagate along some layer of lower velocity in the earth’s interior.
#SEISMAC WAVES FREE#
Love ( L) and Rayleigh ( R) waves which follow the free surface of the earth Surface waves or guided waves, which propagate along some surface. The seismic waves are of two main types:īody waves, which propagate through the interior of the earth. The waves are recorded by seismograph stations the world over, provided that the released energy has been big enough. The seismic or elastic waves, which arise through the sudden rupture in an earthquake source or by an explosion, propagate through the whole of the earth’s interior or along its surface layers. They usually travel slightly faster than the Rayleigh waves.By seismic waves we mean every motion that can be observed on a seismogram, with the exception of direct disturbances of the instruments. Love waves involve the motion of the ground side-to-side, perpendicular to the propagation velocity. They travel at roughly 90% of the speed of the S waves. Rayleigh waves or ground roll waves cause the surface of the ground to move up and down. Love who modeled them - definitely not an indication that anyone is fond of them). Waves whose amplitude of moton is parallel to the surface are called Love waves (named after the mathematician A. The waves which move the surface up and down are called Rayleigh waves and are sometimes described as "ground roll". They are typically more damaging than the P waves because they are several times higher in amplitude.Įarthquakes also produce surface waves which may cause motion perpendicular to the surface or parallel to the surface. S waves travel typically 60% of the speed of P waves. They travel only through solids, and the absence of detected S waves at large distances from earthquakes was the first indication that the Earth has a liquid core. S waves are transverse waves which involve movement of the ground perpendicular to the velocity of propagation. The P waves from an earthquake arrive first, but because of their small amplitudes don't do as much damage as the S waves and surface waves which follow. P waves depend upon the bulk modulus of elasticity for the material as well as its density, and the wave speed in a solid material like granite can be about 5000 m/s. Water can support P waves but not S waves, and the speed of these P waves (speed of sound) in water is about 1450 m/s.
P waves in air are simply sound waves and the speed of sound is around 340 m/s for ordinary temperatures. However, S waves depend upon a resistance to transverse or "shear" force which does not exist in a liquid or gas medium, so they can only travel in the solid parts of the Earth (see geologic example). Since any material, solid or liquid (fluid) is subject to compression, the P waves can travel through any kind of material. For seismic waves through the bulk material the longitudinal or compressional waves are called P waves (for "primary" waves) whereas the transverse waves are callled S waves ("secondary" waves). In a solid material these waves can be either longitudinal waves or transverse waves. The Earth's crust as a solid object will support waves through the crust called body waves and on the surface (surface waves). A disturbance like an earthquake at any point on the Earth will produce energetic waves called seismic waves. Since the Earth or any other planetary body can be considered to be an elastic object, it will support the propagation of traveling waves.
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