pylops.waveeqprocessing.PressureToVelocity¶
-
pylops.waveeqprocessing.
PressureToVelocity
(nt, nr, dt, dr, rho, vel, nffts=(None, None, None), critical=100.0, ntaper=10, topressure=False, dtype='complex128')[source]¶ Pressure to Vertical velocity conversion.
Apply conversion from pressure to vertical velocity seismic wavefield (or vertical velocity to pressure). The input model and data required by the operator should be created by flattening the a wavefield of size \((\lbrack n_{r_y}) \times n_{r_x} \times n_t \rbrack\).
Parameters: - nt :
int
Number of samples along the time axis
- nr :
int
ortuple
Number of samples along the receiver axis (or axes)
- dt :
float
Sampling along the time axis
- dr :
float
ortuple
Sampling(s) along the receiver array
- rho :
float
Density along the receiver array (must be constant)
- vel :
float
Velocity along the receiver array (must be constant)
- nffts :
tuple
, optional Number of samples along the wavenumber and frequency axes
- critical :
float
, optional Percentage of angles to retain in obliquity factor. For example, if
critical=100
only angles below the critical angle \(\sqrt{k_y^2 + k_x^2} < \frac{\omega}{vel}\) will be retained will be retained- ntaper :
float
, optional Number of samples of taper applied to obliquity factor around critical angle
- topressure :
bool
, optional Perform conversion from particle velocity to pressure (
True
) or from pressure to particle velocity (False
)- dtype :
str
, optional Type of elements in input array.
Returns: - Cop :
pylops.LinearOperator
Pressure to particle velocity (or particle velocity to pressure) conversion operator
See also
UpDownComposition2D
- 2D Wavefield composition
UpDownComposition3D
- 3D Wavefield composition
WavefieldDecomposition
- Wavefield decomposition
Notes
A pressure wavefield (\(p(x, t)\)) can be converted into an equivalent vertical particle velocity wavefield (\(v_z(x, t)\)) by applying the following frequency-wavenumber dependant scaling [1]:
\[v_z(k_x, \omega) = \frac{k_z}{\omega \rho} p(k_x, \omega)\]where the vertical wavenumber \(k_z\) is defined as \(k_z=\sqrt{\omega^2/c^2 - k_x^2}\).
Similarly a vertical particle velocity can be converted into an equivalent pressure wavefield by applying the following frequency-wavenumber dependant scaling [1]:
\[p(k_x, \omega) = \frac{\omega \rho}{k_z} v_z(k_x, \omega)\]For 3-dimensional applications the only difference is represented by the vertical wavenumber \(k_z\), which is defined as \(k_z=\sqrt{\omega^2/c^2 - k_x^2 - k_y^2}\).
In both cases, this operator is implemented as a concatanation of a 2 or 3-dimensional forward FFT (
pylops.signalprocessing.FFT2
orpylops.signalprocessing.FFTN
), a weighting matrix implemented viapylops.basicprocessing.Diagonal
, and 2 or 3-dimensional inverse FFT.[1] (1, 2) Wapenaar, K. “Reciprocity properties of one-way propagators”, Geophysics, vol. 63, pp. 1795-1798. 1998. - nt :