Exploring the Parihaka 3D Dataset
The Parihaka 3D dataset in New Zealand’s Taranaki Basin is publicly available through New Zealand Petroleum and Minerals and worth exploring. We reviewed the Near, Mid, Far, and Full Angle Stack volumes, noting the Mid Angle Stack volume had issues with a few traces.
The images included in this posting are tied to the ©Crown Copyright and has been reproduced with permission, from the New Zealand Petroleum and Minerals website at www.nzpam.govt.nz.
Initial display of the Parihaka 3D dataset highlights its impressive quality, though there are some loading and interpretation challenges. Logarithmic histograms are used to capture the full amplitude range, skipping bins with low counts until sufficient data appears. Absolute and alternate min/max amplitudes are stored to flag outliers. Notably, only two traces out of over 1,038,172 had extreme values at the 32-bit float limit. For display, standard deviations of amplitude values were used to ensure a representative view, despite these outliers.
The indexing process scans each trace and sample, logging findings in reports and a JSON file. It flagged 15 traces with missing values in the trace headers, with file positions highlighted in Red. These issues were found at the end of a few lines, and SeisShow excluded them from the index file since they couldn’t be linked to any line or trace.
The sample rate stored in both the Binary and Trace Headers presents another issue. Here, the Trace Headers showed 2049, while the correct value in the Binary Header was 1168. If both headers are off, aligning sample rates across traces can help identify the correct count—a method used in SeisShow and AnalyzeSE to maintain accuracy. This discrepancy is highlighted in yellow in the SeisShow Index, Trace Header, and Report.
Spikes in datasets can disrupt analysis, interpretation, and proper loading into workstations. The previous paragraph discussed this issue. The following images show methods for handling outliers: setting them to zero, clipping, or interpolating traces. SeisShow identifies extreme amplitudes, providing details like line, crossline, x, y, amplitude, time, and trace location. Red arrows highlight spikes, and users can click on high-amplitude lines to jump to their location for review and correction. Interpolation generally yields the best results, while clipping can leave residual spikes in quieter areas. There’s also an option to write out the edited file for further adjustments.
Included are two more displays: the SeisShow Report and a well-documented EBCDIC header.
Have you encountered problems with bad trace header values or amplitude spikes? Please share your experiences in the comments on LinkedIn.
About Don Robinson
Don Robinson has dedicated over 50 years to software development and seismic analysis. He founded Oklahoma Seismic Corporation in 1980 and co-developed the MIRA interpretation system, later acquired by Landmark Graphics in 1993. He then started Resolve GeoSciences in 1997, where he now leads the development of SeisShow and AnalyzeSE, software for analyzing and correcting SEG-Y seismic data.
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