Nankai Data: Examine, Resample, Sort, Gain
We are going to process a real 2-D line of seismic data provided by Prof. Greg Moore of the University of Hawaii. The data were collected near the coast of Japan, over the Nankai trough, where the Philippines plate is subducting beneath Eurasia. The “Nankai” data were collected by the University of Texas, the University of Tulsa, and the University of Tokyo. Based on this data set, a paper was published (Moore, et al., 1990) in which this line is called NT62-8.
The following Nankai seismic files are available:
Below is the surange output of Nshots.su.
Keys tracl and tracr number the 19057 traces (although they use different starting numbers).
Key fldr tells us there are 326 shot gathers (2012-1687+1).
Since the number of samples per trace (ns) is 5500 and the trace sample interval (dt) is 2000 microseconds, the trace length is 11 seconds (5500 samples/trace x 0.002 seconds/sample)
Notice that the Nankai shot gather trace headers already contain cdp values.
Below is a chart of the number of traces per shot gather (Figure 10.1). (We describe the program, sukeycount, which generated the data for the figure in Appendix C.) The first shot gather, 1687, has one trace, then the number of traces per gather increases to a maximum of 69 at gather 1735. This is constant through gather 1965. After gather 1965, the number of traces per gather steadily decreases to 1 at the last gather, 2012.
Below is the surange output of Nstack.su. This stack file (Figure