What does seismic velocity depend on?
Ultimately, seismic velocity depends on the density and elastic properties of the material, whatever its composition. Specifically, Compressional-wave velocity depends on the “incompressibility” of the material, as embodied in the bulk modulus.
What are seismic velocities?
1. n. [Geophysics] The rate at which a seismic wave travels through a medium, that is, distance divided by traveltime. Seismic velocity can be determined from vertical seismic profiles or from velocity analysis of seismic data.
What factors affect seismic wave velocity?
Composition, temperature, and pressure are all factors that can affect seismic velocity in the mantle. Laboratory elasticity data show that a decrease of 1% in the Mg/(Mg+Fe) ratio in olivine reduces the velocity by an amount equivalent to that caused by a temperature increase of 70 K.
What is the seismic velocity of water?
1500 m/s
The main factors affecting seismic exploration is the propagation velocity of seismic waves in the medium. In the past, during marine seismic data processing, the propagation velocity of sea water was generally taken as a constant 1500 m/s.
What is the most important factor in determining seismic velocity in rocks?
The most significant factor affecting seismic wave velocities is porosity. In the above table, we saw that seismic waves travel faster in solids than they do in fluids; with S-waves being unable to propagate through fluids. Thus as the porosity of a rock increases, both the P-wave and S-wave velocities will decrease.
Why does seismic velocity increase with depth?
Seismic velocities tend to gradually increase with depth in the mantle due to the increasing pressure, and therefore density, with depth. However, seismic waves recorded at distances corresponding to depths of around 100 km to 250 km arrive later than expected indicating a zone of low seismic wave velocity.
Which seismic waves have the highest average velocity?
P-waves are the first waves to arrive on a complete record of ground shaking because they travel the fastest (their name derives from this fact – P is an abbreviation for primary, first wave to arrive). They typically travel at speeds between ~1 and ~14 km/sec.
How do you find the velocity of a seismic wave?
The velocity of the wave is determined by the physical properties of the material through which it propagates. In the case of a vibrating string, c2 = F/ρ where F is the string tension force and ρ is the density.
What is seismic velocity of rocks?
seismic velocity: The speed with which an elastic wave propagates through a medium. For non-dispersive body waves, the seismic velocity is equal to both the phase and group velocities; for dispersive surface waves, the seismic velocity is usually taken to be the phase velocity.
How does pressure affect seismic velocity?
As the effective pressure increases the cracks are all closed, K goes up and the velocity increases. Finally even at depth, as the pore pressure increases above hydrostatic, the effective pressure decreases as does the velocity.