sfpick performs automatic picking from semblance-like panels.

The underlying algorithm is described in

Appendix B of the paper

Velocity analysis using AB semblance and is inspired by the method of virtual endoscopy in medical imaging.

The following example from

tccs/avo/avo shows an automatic pick through AB semblance.

If

**smooth=n**, the program picks an optimal path through the panel but does not try to smooth it. If

**smooth=y** (the default), the picked path is additionally smoothed using

shaping regularization. The smoothing radius across different dimensions is controled by

**rect1=**,

**rect2=**, etc. parameters. The number of shaping iterations is specified by

**niter=**.

The following example from

sep/vc2/beivc shows two different picks for two different values of the

**rect1=** parameter

The

**vel0=** refers to the value the pick initially takes at the surface (the origin). This value is not necessarily preserved, because it can get modified by smoothing. In the following example from

tccs/timelapse/timelapse,

**vel0=1**.

The

**an=** parameter controls the anisotropy between the two axes of the semblance panel. Varying this parameter, you can achieve picks that are more rigid or more flexible. The

**gate=** parameter controls how far (in velocity samples) the pick can swing between two neighboring time samples. Changing its value also affects the flexibility of the picked trend.

For picking from 3-D (rather than 2-D) panels, try

sfpick3.

### Previous programs of the month:

sfiwarp performs mapping between different coordinates. If you have sampled functions f(x) and y(x), sfiwarp with inv=y (the default) finds sampled f(y). If inv=n, sfiwarp takes f(y) and y(x) and finds f(x). In both cases, the sampled y(x) function is sup

Weblog:Madagascar development blogTracked:Sep 09, 12:52sfkirmod is a program for modeling seismic reflection data using the Kirchhoff method. According to this method, the reflection response is computed by integrating over the reflector surface. For a theoretical derivation, see, for example, Haddon, R. A

Weblog:Madagascar development blogTracked:Oct 13, 19:46sfbandpass implements bandpass filtering using the Butterworth algorithm. The desired bandwidth is specified by low and high frequencies (in Hertz) flo= and fhi=. A continuous low-pass Butterworth filter is given by The actual filtering is imp

Weblog:Madagascar development blogTracked:Nov 18, 13:45sfhalfint implements half-order integration or differentiation, a filtering operation common in 2-D imaging operators such as as slant stacking or Kirchhoff migration. By default, sfhalfint performs half-order integration. To apply half-order different

Weblog:Madagascar development blogTracked:Jan 06, 16:58sfricker1 implements 1-D convolution with the Ricker wavelet. The following example from rsf/rsf/wedge shows convolution modeling with a wedge model using sfricker1. The convolution is implemented in the frequency domain, where the Ricker wavele

Weblog:Madagascar development blogTracked:Jan 18, 12:49sfricker1 implements 1-D convolution with the Ricker wavelet. The following example from rsf/rsf/wedge shows convolution modeling with a wedge model using sfricker1. The convolution is implemented in the frequency domain, where the Ricker wavele

Weblog:Madagascar development blogTracked:Jan 19, 12:00sfpwd implements plane-wave destruction, a filter that attenuates locally plane-wave events, as described in the paper Applications of plane-wave destruction filters. The following example from jsg/diffr/gom shows a seismic section before and after an

Weblog:Madagascar development blogTracked:Feb 09, 16:20sfpow multiplies the input data by a gain function of the form Gx1x2…,xn=x1p1x2p2⋯xnpn The powers p1,p2,…,pn are given by pow1=, pow2=, etc. parameters. For backward compatibility, sftpow tpow= is an alias for sfpow pow1=. The following examp

Weblog:Madagascar development blogTracked:Mar 11, 09:02sfnmo implements normal moveout (NMO) correction, one of the most fundamental operations in seismic reflection data processing. The following example from jsg/avo/avo shows synthetic data before and after NMO correction. NMO transforms presta

Weblog:Madagascar development blogTracked:Apr 08, 06:02sfvscan implements seismic velocity analysis by scanning stacking velocities. This transformation is also known as the velocity transform or the hyperbolic Radon transform. The following example from bei/vela/vscan shows an example for transforming a C

Weblog:Madagascar development blogTracked:May 11, 12:25sfwiggle plots data using the traditional seismic method of wiggly traces. The following example from rsf/rsf/rsftour shows a typical output: Similarly to other plotting programs, there are multiple parameters that control the output. For examp

Weblog:Madagascar development blogTracked:Jun 12, 10:51sfwiggle plots data using the traditional seismic method of wiggly traces. The following example from rsf/rsf/rsftour shows a typical output: Similarly to other plotting programs, there are multiple parameters that control the output. For examp

Weblog:Madagascar development blogTracked:Jun 12, 10:59