Reflection seismic study of the post-glacial Burträsk fault: Original stack

In 2008, a 22 km long high resolution reflection seismic profile was acquired over the Burträsk fault in Northern Sweden. The Burträsk fault formed at the end of the last glacial, triggered by the rapid melting of the Scandinavian ice sheet and the following crustal rebound. The aim of the survey was to image the structure of the fault with depth. The profile followed existing roads resulting in a very crooked acquisition geometry. A list of the key acquisition parameters is given below. The dataset was first processed and published in 2011. In 2018, the dataset was reprocessed using an additional cross-dip correction step to improve the imaging of reflection with a dip component in the cross-profile direction. The following data files are available for downloading: 1) raw shot gathers (decoded and quality controlled, with geometry information in the headers) 2) original stacked section from Juhlin and Lund (2011) 3) cross-dip corrected stacked section from Beckel and Juhlin (2019) 4) cross-dip corrected migrated section from Beckel and Juhlin (2019) A short summary of the main processing steps for each dataset is given below. For a complete description, please refer to the above mentioned publications. Key acquisition parameters: Number of channels: 280 Near offset: 0 m Geophone spacing: 20 m Geophone type : 28 Hz single Nominal source spacing : 20 m Source type : VIBSIST Hit interval between hammer blows : 100-200 ms Sweeps per source point :3-4 Nominal fold : 140 Recording instrument : SERCEL 408L Sample rate : 1ms Field low cut : Out Field high cut : 400 Hz Record length : 23 s Profile length : 22 km Source points : 799 Dates acquired: 2008/08/05-2008/08/16 Short summary of the main processing steps: 1) BUR_shots_geom.sgy The raw shot records are pre-processed with VIBSIST decoding, quality control. Information about the shot and receiver geometry has been added to the trace headers. 2) BUR_original_stack.sgy The processing flow of the original data stack includes trace editing and balancing, spectral equalization, time-variant bandpass filtering, refraction and residual statics, horizontal median filtering, NMO correction, DMO correction, stacking and coherency filtering (for a complete description see Juhlin & Lund, 2011) 3) BUR_crossdip_stack.sgy The main processing steps of the crossdip stack are very similar to those of the original stack, including trace editing and balancing, spectral equalization, time-variant bandpass filtering, refraction and residual statics, horizontal median filtering, NMO correction, DMO correction, stacking and coherency filtering. Before DMO correction, an additional cross-dip correction step has been added. For a complete description see Beckel & Juhlin, 2019. 4) BUR_crossdip_mig.sgy The processing flow of the migrated section includes trace editing and balancing, spectral equalization, time-variant bandpass filtering, refraction and residual statics, horizontal median filtering, NMO correction, cross-dip correction, DMO correction, stacking, coherency filtering and migration (for a complete description see Beckel & Juhlin, 2019). This dataset contains the original stack of the Burträsk profile (Juhlin & Lund, 2011). Processing steps for this data set: 1. Read decoded VIBSIST data 2. Bulk static shift to zero time 3. Apply geometry 4. Pick first breaks 5. Resample: 2 ms, 1501 samples 6. Trace editing 7. Trace balance: 0-3000 ms 8. Spectral equalization: 25-40-120-150 Hz 9. Time variant bandpass filter: 0-200 ms: 35-70-200-300 Hz 250-500 ms: 30-60-180-270 Hz 600-900 ms: 22-45-135-200 Hz 1100-3000 ms: 20-40-120-180 Hz 10. Refraction statics: datum 200 m, replacement velocity 5500 m s-1, overburden velocity 1600 m s -1 11. Residual statics 12. AGC: 100 ms window 13. Median filter: 11 traces, 3 samples, 5300 m s-1 , subtract 14. Butterworth filter: 20-40-200-300 15. Residual statics 16. Velocity analysis 17. NMO correction: 40% stretch mute 18. DMO 19. Stack 20. Trace balance 21. FX Decon: 19 trace window Processed seismic data stored as one file for the entire seismic profile, according to SEG technical standard SEG-Y revision 1 (SEG-Y_r1.0, 2002); https://seg.org/Publications/SEG-Technical-StandardsOpens in a new tab