{"id":339,"date":"2013-07-01T22:26:00","date_gmt":"2013-07-01T22:26:00","guid":{"rendered":"http:\/\/ahay.org\/blog\/?p=339"},"modified":"2015-08-31T03:24:32","modified_gmt":"2015-08-31T03:24:32","slug":"program-of-the-month-sftime2depth","status":"publish","type":"post","link":"https:\/\/ahay.org\/blog\/2013\/07\/01\/program-of-the-month-sftime2depth\/","title":{"rendered":"Program of the month: sftime2depth"},"content":{"rendered":"

sftime2depth<\/a> converts the input from vertical time to depth coordinates. <\/p>\n

The following example from rsf\/su\/rsflab9<\/a> shows a seismic image converted from time to depth by this transformation: <\/p>\n

\"\" \"\" <\/p>\n

The example is borrowed from John Stockwell’s lecture notes on Geophysical Image Processing<\/a> and translated from Seismic Unix<\/a> to Madagascar. The transformation follows the simple equation
\n$$t = 2\\,\\int\\limits_{0}^{z} \\frac{d\\zeta}{v(\\zeta)}$$,
\nwhere $t$ is two-way vertical time, $z$ is depth, and $v(z)$ is vertical velocity. <\/p>\n

The sampling of the output depth axis is controlled by nz=<\/strong>, dz=<\/strong>, and z0=<\/strong>. If the velocity (provided in the auxiliary velocity=<\/strong> file) is sampled in time rather than depth, use intime=y<\/strong>. If it is slowness rather than velocity, use slow=y<\/strong>. If the input is in one-way time rather than two-way time, use twoway=n<\/strong>. The interpolation is carried out using B-splines<\/a>. The spline order is controlled by extend=<\/strong>. By default, cubic splines (extend=4<\/strong>) are used. <\/p>\n

The inverse transformation is given by sfdepth2time<\/a>. <\/p>\n

In the presence of lateral velocity variations, the correct transformation from time to depth is not as simple and needs additional corrections. See Time-to-depth conversion and seismic velocity estimation using time-migration velocity<\/a>. <\/p>\n

10 previous programs of the month<\/h3>\n