OASP3D Options

Except for the specification of source type, OASP3D Version 3.6 is compatible with OASP Version 1.6 in terms of options supported:

C

Creates an representation of the field in the form of contours of integration kernels as function of horizontal wavenumber (slowness if option B is selected) and frequency (logarithmic y-axis). All axis parameters are determined automatically.

K

Computes the bulk stress. In elastic media the bulk stress only has contributions from the compressional potential. In fluid media the bulk stress is equal to the negative of the pressure. Therefore for fluids this option yields the same result as option N or R.

O

Complex frequency integration contour. This new option is the frequency equivalent of the complex wavenumber integration (J option in OAST). It moves the frequency contour away from the real axis by an amount reducing the time domain wrap-around by a factor 50 [3]. This option can yield significant computational savings in cases where the received signal has a long time duration, and only the initial part is of interest, since it allows for selection of a time window shorter than the actual signal duration. Note that only wrap around from later times is reduced; therefore the time window should always be selected to contain the beginning of the signal!

R

Computes the radial normal stress (or for plane geometry).

S

Computes the shear stresses and . In PP these components are selected for display by 'X' and 'Y', respectively, under the ``Parameter'' selection options.

U

Decomposed seismograms. This option generates 7 transfer function files to be processed by PP:

File name	Contents
input.trf	Complete transfer functions
input.trfdc	Downgoing P waves
input.trfuc	Upgoing P waves
input.trfds	Downgoing SV waves
input.trfus	Upgoing SV waves
input.trfdh	Downgoing SH waves
input.trfuh	Upgoing SH waves

f

Full Bessel function integration. This new option does not apply the asymptotic representation of the Bessel function in the evaluation of the inverse Hankel transforms. The implementation is very efficient, and the integral evaluation is performed just as fast as the asymptotic evaluations. It is more sensitive to truncation, however, and therefore usually requires a much larger wavenumber interval to avoid truncation arrivals. Further, the Bessel function represents both outgoing and incoming waves, such that the periodicity of the discrete integral transforms introduces false arrivals from the periodic sources. It is therefore recommended to solely apply this option for cases where very steep propagation angles are important, e.g. short offset VSP computations. For all other cases the asymptotic Filon (option F) is highly recommended.

l

User defined source array. This new option is similar to option L in the sense that that it introduces a vertical source array of time delayed sources of identical type. However, this option allows the depth, amplitude and delay time to be specified individually for each source in the array. The source data should be provided in a separate file, input.src, in the format described below in Section 10.3.2.

v

As option l this option allows for specifying a non-standard source array. However, it is more general in the sense that different types of sources can be applied in the same array, and the sources can have different signatures. The array geometry and the complex amplitudes are specified in a file input.strf which should be of trf format as described in Section 10.3.2.

t

Eliminates the wavenumber integration and computes transfer functions for individual slowness components (or plane wave components). The Fourier transform performed in PP will then directly compute the slowness/intercept-time or response for each of the selected depths. When option t is selected, the range parameters in the data file are insignificant.