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.
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 P wave velocity of dry sand?
The quite slow P-wave velocity (around 160 m sā1) in sand allows us to perform far field measurements in a 1-m long sample since wavelengths are around 0.1 m for a working frequency near 1.6 kHz, these wavelengths being 1000 times larger than the grain size.
How do you measure seismic velocity?
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 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.
What is seismic velocity analysis?
Velocity analysis is a step in the seismic data processing with the objective to determine the seismic velocity of a given medium, for example, a medium arranged in layers. Its result directly influences the steps of stacking and migration.
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.
What is the velocity of P waves?
The p-wave velocity at the upper most mantle is 7.97 km/s, and the S-wave 4.55 km/s. The low velocity layer in the upper mantle occurs approximately at 140 km deep with a thickness of about 55ā62 km.
What is the velocity of granite?
The geological significance of granite velocities and elastic constants is discussed. It is concluded that a longitudinal-wave speed of 5.5 km/sec.
Which factors affect seismic 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 velocity analysis used for?
Velocity Analysis is the calculation of stacking velocity (Vs) or normal moveout velocity (Vnmo) from measurements of normal moveout (Sheriff, 1991). As the source to geophone distance increases the time for a signal to arrive increases, and when plotted on a time vs distance graph the data forms a hyperbola.