Multichannel Seismic-Reflection and Navigation Data Collected Using Sercel GI Guns and Geometrics GeoEel Digital Streamers During the Mid-Atlantic Resource Imaging Experiment (MATRIX), USGS Field Activity 2018-002-FA

PROCESS STEP 1:
Shearwater Reveal (version 4.1) seismic processing software was used to execute the following processing flows to produce the raw shot SEG-Y files.
1. Import SEG-D sequences: SegDRead read raw Geometrics SEG-D shot sequence files, extracted navigation fixes from the external headers, and wrote them to new header words. HeaderMath wrote a delay time header word when necessary (2 seconds for sequence B01A of MX01 and A01A of MX12), a raw trace length header word, and converted the source lat/lon positions from seconds of arc to decimal degrees (NRP_LAT, NRP_LON). UTMLatLong projected the geographic navigation to UTM Zone 18N WGS 84 meters (NRP_X, and NRP_Y). Output wrote the trace sequence to Reveal formatted ".seis" files.
2. Resample: RES resampled traces in the first two sequences of MX01 from 0.5 to 1 ms.
3. Layback geometry assignment: Input read sequence files sorted by FFID/CHANNEL. The Python module ShotlineLayback (developed by Nathan Miller of USGS-WHCMSC) defined the source and streamer geometry based on measured horizontal offsets from the NRP to the center of the sources (cos) and the centers of the first and last 6.25 m spaced channel groups, and when necessary, the first and last 12.5 m spaced channel groups on the active streamer section. The following table lists the linear offsets from the NRP to center of source (COS) and index channels (IC) used to define layback geometry by line.
NRP to COS offset,NRP to IC offset(IC#) - Linelist -47.8,-174.6(1)/-922.69(120)/-932.38(121)/-1320.81(152) - Line MX01 -47.8,-176.6(1)/-924.69(120)/-934.38(121)/-1322.81(152) - Lines MX02 and MX03 -47.8,-176.6(1)/-874.38(112) - Lines MX04 - MX10 -47.8,-176.6(1)/-975(128)/-984.69(129)/-1373.12(160) - Lines MX11 - MX17 -47.8,-176.6(1)/-975(128)/-984.69(129)/-1272.56(152) - Lines MX18 and MX19
The module interpolated a sail line from the shot NRP positions (NRP_X and NRP_Y), then computed layback positions for the source and channel groups (values were interpolated for all channels in between the defined index channels) for each FFID by translating them back along the sail line by their respective offsets. Layback midpoint positions along the sail line were also computed for each shot/receiver pair. HeaderMath computed and populated a new header word for trace offset using OFFSET = ABS(NRP2CHAN) - ABS(NRP2COS). Output wrote the trace sequence with defined geometry to new files.
4. Merge sequence files, remove delay, and set trace length: These processes were only necessary for a subset of the lines. Lines MX01, MX02, MX03, and MX12 were each compiled from multiple sequences that were acquired with variable trace lengths and delays. DissimilarInput allowed the sequences to be merged by line despite the differences, then TraceLength set a common trace length encompassing all inputs and ApplyStatic shifted traces with deep water delays to the appropriate origin times (a recording delay of 2 s was used for one sequence in lines MX01 and MX12). DBWrite wrote the layback geometry source positions (in UTM 18N WGS84 meters and geographic decimal degrees), FFID number, year, day number, and UTC times for the shots in each merged line to ASCII CSV files. Output wrote the merged lines to new files.
5. Define CMP bins: Survey lines were created in the Reveal project grid using a subset of NRP northing and easting coordinates to define crooked line binning geometries. Rectangular bins were defined along the survey tracks with along-track lengths of 3.125 m and crossline widths of 1000 m (centered on the survey track). Because lead in bins were included prior to shot locations for some lines, several stacked lines start with CMP numbers greater than one.
6. Geometry modification for tailbuoy navigation: Tailbuoy GPS navigation acquired during lines MX01 to MX07 and MX11 to MX19 were used to adjust the streamer geometry to incorporate trigonometrically estimated streamer feather into the CMP binning process. Input read the layback geometry files. Text files containing tailbuoy positions and UTC times extracted from HYPACK raw files were used as inputs for DBmerge, which matched times in the trace headers to times in the tailbuoy navigation file (through interpolation) and inserted tailbuoy positions into the trace headers (TB_LON and TB_LAT). UTMLatLong projected the geographic tailbuoy positions to WGS84 UTM Zone 18N meters (TB_X and TB_Y). HeaderMath estimated the streamer feather azimuth relative to the NRP using CABLE_AZ_RAD = atan2(NRP_Y - TB_Y, NRP_X - TB_X), then calculated new layback and feather adjusted source and receiver positions using SRC_X = NRP_X + NRP2COS * cos(CABLE_AZ_RAD), SRC_Y = NRP_Y + NRP2COS * sin(CABLE_AZ_RAD), REC_X = NRP_X + NRP2CHAN * cos(CABLE_AZ_RAD), REC_Y = NRP_Y + NRP2CHAN * sin(CABLE_AZ_RAD). DBWrite wrote the feather adjusted source positions (in UTM 18N WGS84 meters and geographic decimal degrees), FFID number, year, day number, and UTC times for the shots in each line to ASCII CSV files. Output wrote the lines with streamer feather adjusted geometry to new files.
7. Assign Common Midpoints: Input read files with (MX01 - MX07 and MX11 - MX19) or without (MX08 - MX10) streamer feather adjusted geometry. HeaderSetup computed new source/receiver pair midpoint positions for lines with streamer feather adjusted geometry, and also assigned traces to CMP bins and computed CMP bin positions (BIN_X and BIN_Y) for all lines using the project grid binning geometries defined in step 5. Output wrote the lines with assigned CMPs to new files.
8. Assign static corrections: FFID's 1306 - 3311 of line MX03 required a static shift of -102 milliseconds (ms) due to unintentional application of a delay time while temporarily triggering on distance through the Geometrics controller. Additionally, readings from RBRSolo-D pressure depth recorders spaced along the streamer were inserted into the trace headers for all lines. Input read the geometry corrected trace files. Text files prepared to contain UTC time, offset location of the pressure depth probe along the streamer, and pressure depth values in meters were used as inputs for DBMerge, which matched times and trace offsets in the trace headers with those in the input text files (through interpolation) and populated a new receiver depth header word with pressure depth values for each channel of the active section. HeaderMath also populated a new header word containing a constant source depth value of 3 m (dictated by the rigging of the airgun strings), then converted both static values from meters to milliseconds (dividing by an assumed water column sound speed velocity of 1.514 m/ms) and wrote them to new header words. The source/receiver static values have not been applied to the traces. For line MX03, HeaderMath inserted the -102 ms value into the appropriate trace headers and ApplyStatic shifted the traces to match the remainder of the file. Output wrote the traces including static corrections to new files.
9. SEG-Y output: Input read the files including static corrections. ButterworthPy applied a highpass butterworth filter (> 20 Hz with 4 corners). Mute applied top and bottom mutes at 60 ms beyond the trace start time (10 ms taper) and 20 ms less that the trace end time (30 ms taper), respectively. UTMLatLong projected source, receiver, and CMP bin positions from UTM Zone 18N WGS 84 meters to geographic and wrote them to new header words. HeaderMath converted the geographic coordinates from decimal degrees to seconds of arc multiplied by 100 and set the coordinate unit header to 2 accordingly, also scaled the source, receiver, and applied static header values (in meters) by 100, and finally set the time basis code to 2 for UTC. Output wrote the raw shot traces with defined geometry and static corrections to SEG-Y Rev. 1 format (32-Bit IBM floating point). Each output SEG-Y file contains a textural file header similar to the example from line MX01 included below.
Though Wayne Baldwin is listed as the primary contact, shipboard and post-cruise processing were also conducted by Nathan Miller and David Foster.
Example raw shot file SEG-Y Textural Header:
C 1 U. S. GEOLOGICAL SURVEY COASTAL AND MARINE HAZARDS AND RESOURCES PROGRAM
C 2 SURVEY_ID: 2018-002-FA AREA: US ATLANTIC MARGIN VESSEL: R/V HUGH R. SHARP
C 3 YEAR: 2018 LINENAME: MX01
C 4
C 5 ACQUISITION: UP TO 4 x 105 CU IN AIR GUNS, 30 METER SHOT INTERVAL,
C 6 1.156-KM, 152 CHANNEL GEOEEL HYDROPHONE STREAMER (6.25 AND 12.5 M GROUPS),
C 7 0.5 OR 1 MS RECORDING SAMPLE INTERVAL, 6 OR 10 SEC RECORD LENGTHS,
C 8 RECORDING DELAY OF 2 SEC FOR FFIDS 1583-2090 (PROBLEM WITH 1583-1586),
C 9 RECORDED IN SEG-D FORMAT. SOURCE CHANGES THROUGHOUT WHILE TROUBLESHOOTING.
C10
C11 PROCESSING: IMPORT SEG-D SEQUENCE FILES, RESAMPLE TO 1.0 MS, DEFINE CROOKED
C12 LINE CMP BINS (1-KM WIDE AND SPACED 3.125-M) USING NRP NAVIGATION, MERGE
C13 SEQUENCE FILES, REMOVE DELAY AND SET TRACE LENGTH, ASSIGN SRC/REC/MIDPOINT
C14 GEOMETRY USING TAIL BUOY GPS NAVIGATION, ASSIGN CMPS, ASSIGN SRC/REC STATIC
C15 CORRECTIONS, BUTTERWORTH FREQUENCY DOMAIN HIGHPASS FILTER (> 20 HZ), TOP
C16 MUTE (TRACE START + 60 MS, 10 MS TAPER), BOTTOM MUTE (TRACE END - 20 MS,
C17 30 MS TAPER).
C18
C19 OUTPUT: 32-BIT IBM FLOATING POINT SEG-Y
C20 RECORD LENGTH: 5.9 SEC (DATA LENGTH 3.9 SEC FOR FFIDS 1583-2090)
C21
C22 SRC/GRP/CDP COORDINATES ARE STORED IN GEOGRAPHIC ARCSECONDS (SCALED BY 100)
C23 DIVIDE BY 360000 FOR DECIMAL DEGREES.
C24 COORDINATE SCALAR IN BYTES 71-72
C25 SRC-X AND SRC-Y IN BYTES 73-76 AND 77-80
C26 GRP-X AND GRP-Y IN BYTES 81-84 AND 85-88
C27 CDP-X AND CDP-Y IN BYTES 181-184 AND 185-188
C28 CDP NUMBER STORED IN BYTES 21-24
C29
C30 SRC STATIC CONSTANT FROM RIGGING, GRP STATICS MEASURED BY 6 PRESSURE DEPTH
C31 LOGGERS EVENLY SPACED ALONG STREAMER WITH VALUES INTERPOLATED LINEARLY
C32 TO ALL CHANNELS.
C33 SRC AND GRP STATIC CORRECTIONS (SCALED BY 100 AND NOT APPLIED)
C34 SRC-STATIC IN BYTES 99-100
C35 GRP-STATIC IN BYTES 101-102
C36
C37 FOR ADDITIONAL INFORMATION CONCERNING THIS DATASET REFER TO THE ASSOCIATED
C38 USGS SCIENCEBASE DATA RELEASE ONLINE AT:
C39 HTTPS://DOI.ORG/10.5066/P91WP1RZ
C40

PROCESS STEP 2:
Shearwater Reveal (version 4.1) seismic processing software was used to execute the following processing flows to produce SEG-Y files of profiles processed through post-stack time migration.
1. Trace preprocessing and noise reduction: Import read files with geometry and static corrections. HeaderMath converted the cumulative source/receiver statics in meters to milliseconds by SRC_REC_STAT = (SRC_DEPTH + REC_DEPTH)/1.514 (assumed water column sound speed velocity in m/ms) and wrote them to new header words, and ApplyStatic shifted traces by the computed times. Despike estimated local median values within 600 ms windows then used the median values to replace samples that exceeded them by 10 times. SphericalDivergence scaled traces using an offset dependent correction. TraceLength set new trace start times and lengths for profiles in which the entire raw trace length was not used for processing (lines MX01, MX11 - MX19). FXSwell and FXDecon targeted low frequency noise (below 30 Hz) and random noise, respectively, using FX filtering. A polygonal FKFilter rejected noise energy identified in shot gather f-k spectra. Output wrote preprocessed, noise-reduced traces to new files.
2. Constant velocity stack, sea floor picking, and 1D velocity model creation: To produce a quality control stack, Input read the preprocessed, noise-reduced traces, Bandpass filtered the data to 20-450 Hz, NormalMoveout converted traces to zero offset assuming a constant 1514 m/s sound speed through water, Stack produced a single trace per CMP bin, and Output wrote the stacked traces to new files. Sea floor reflection times were predicted for each line and saved to new database files. 1D velocity models hung from the sea floor reflection were created using subsurface velocity gradient information for this portion of the U.S. Atlantic margin derived from semblance analysis of 2D seismic data shot during R/V Marcus Langseth cruise MGL1407 (Arsenault and others, 2017). Input read the quality control stack traces, VelocityLayer created four subsurface layers of variable velocity gradient per trace initiated at set subsurface two-way travel times (0 ms and 0.12755 1/ms, 196 ms and 0.07462687 1/ms, 230 ms and 0.2089 1/ms, and 320 ms and 0.347222 1/ms) that combined to equal the input trace length, ApplyStatic shifted the velocity gradient traces by the predicted sea floor time, TraceMath calculated the velocities by trace sample using sample = sample (increasing by gradients) + 1514 (resulting in a water column sound speed velocity of 1514 m/s that then increased by the defined gradients extending into the subsurface), and Trace2Table wrote the 1D velocity models to new database tables for use in subsequent NormalMoveout and PostStackMigration operations.
3. Source wavelet extraction: Input read the preprocessed, noise-reduced files. In preparation for source wavelet extraction, Deghost2D was used to estimate and attenuate source and receiver side ghost reflections from the input traces. ExtractWavelet extracted a minimum-phase wavelet from the input traces, and Output wrote the source wavelet to a new file.
4. Source wavelet designature: Input read the preprocessed, noise-reduced files. Designature utilized the extracted source wavelet to estimate a zero-phase, whitened and bandpass filtered (20-30-400-450 Hz) inverse filter that was used to designature the input traces. Deghost2D was used to estimate and attenuate source and receiver side ghost reflections. Output wrote the designatured and deghosted traces to new files.
5. 2D velocity model from semblance and surface related multiple extraction (SRME): These processes were limited to near-shelf, along-strike profiles (lines MX06, MX10, MX11, and MX19) where topographic variability associated with shelf-edge canyon traverses made the approach of hanging a layered 1D velocity model from the sea floor less appropriate, and shallow-section multiple energy particularly distracted from primary stratigraphy.
A. 2D velocities were picked using an interactive Reveal semblance picking flow. Input read the designatured and deghosted files. Velocities were picked from Semblance generated on CMP gathers and evaluated by their effects on in line NormalMoveout and VelocityStack results. Picks were made from approximately 500 CMP intervals or less in sections where sea floor topography changed significantly. Picks shallower than the sea floor were set to a water column sound speed of 1514 m/s. Final picks were saved to Reveal database tables by line.
B. In preparation for SRME, Input read the designatured and deghosted trace files limited to the 6.25 m group spaced portions of the active section (ie. the first 112 or 128 channels), SRMEPrepOffsets inserted place-holder traces for missing or dead traces in the shot domain, SphericalDivergence removed the previously applied offset dependent correction, SRMENearExtrap filled near offset traces using tau-p in the CMP domain, Mute applied a top mute to all traces just prior to the sea floor time, SRMEShotInterp interpolated shots in order to fill any missing shots and produce as consistent shot/receiver spacing as possible, SRMEPredict created traces containing predictions of multiple energy for each input shot record, and Output wrote the results to new multiple prediction files. SRME multiple reduction involved a multiport process in which Input read the designatured and deghosted and predicted multiple files in two parallel branches, static application and top mutes were applied to the designatured and deghosted traces the same as during preparation, SRMESubtract performed shot by shot comparison of the designatured and deghosted and predicted multiple traces to produce refined filtered multiple operators that were passed along to a second SRMESubtract process which subtracted the refined predicted multiple energy from the designatured and deghosted data. Finally, the offset dependant SphericalDivergence correction was reapplied and Output wrote the designatured, deghosted, and multiple-reduced data to new files.
6. Processed stack: Input read either the designatured and deghosted or designatured, deghosted, and multiple-reduced files sorted to CMP, NormalMoveout converted traces to zero offset using either the 1D or 2D velocity model created for each file, Stack produced a single trace per CMP bin, and Output wrote the stacked traces to new files.
7. Post-stack time migration: Input read the stacked files, PostStackMigration performed a phase-shift time migration using the 1D or 2D velocity model created for each file (450 Hz maximum frequency and 3.125 m bin spacing), and Output wrote the migrated stacked traces to new files. Subsequent to migration, the predicted sea floor picks were overlaid on the migrated trace display, manually adjusted to more closely approximate the migrated sea floor, and saved to new files.
8. SEG-Y output: Input read the migrated stacked files. Table2Header wrote the modified sea floor picks to a water bottom time header word. Mute applied a top mute at the water bottom time. UTMLatLong projected the CMP bin positions from UTM Zone 18N WGS 84 meters to geographic and wrote them to new header words. HeaderMath inserted dead traces for empty CMPs and set their trace type to 3 accordingly, converted the geographic coordinates from decimal degrees to seconds of arc multiplied by a scaler of 100, and set the coordinate unit header to 2 accordingly. DBWrite wrote the CMP positions (in UTM 18N WGS84 meters and geogpraphic decimal degrees), CMP number, year, and fold header words to ASCII CSV text files by line. Output wrote the migrated, stacked traces to SEG-Y Rev. 1 format (32-Bit IBM floating point). Each output SEG-Y file contains a textural file header similar to the example from line MX01 included below.
Example migrated stacked file SEG-Y Textural File Header:
C 1 U.S. GEOLOGICAL SURVEY COASTAL AND MARINE HAZARDS AND RESOURCES PROGRAM
C 2 SURVEY_ID: 2018-002-FA AREA: US ATLANTIC MARGIN VESSEL: R/V HUGH R. SHARP
C 3 YEAR: 2018 LINENAME: MX01
C 4
C 5 ACQUISITION: UP TO 4 x 105 CU IN AIR GUNS, 30 METER SHOT INTERVAL,
C 6 1.156-KM, 152 CHANNEL GEOEEL HYDROPHONE STREAMER (6.25 AND 12.5 M GROUPS),
C 7 0.5 OR 1 MS RECORDING SAMPLE INTERVAL, 6 OR 10 SEC RECORD LENGTHS,
C 8 RECORDING DELAY OF 2 SEC FOR FFIDS 1583-2090 (PROBLEM WITH 1583-1586),
C 9 RECORDED IN SEG-D FORMAT. SOURCE CHANGES THROUGHOUT WHILE TROUBLESHOOTING.
C10
C11 PROCESSING: IMPORT SEG-D SEQUENCE FILES, RESAMPLE TO 1.0 MS, DEFINE CROOKED
C12 LINE CMP BINS (1-KM WIDE AND SPACED 3.125-M) USING NRP NAVIGATION, REMOVE
C13 DELAY (2 S) AND SET TRACE LENGTH (10 S), MERGE SEQUENCE FILES, ASSIGN
C14 SRC/REC/MIDPOINT GEOMETRY USING TAIL BUOY GPS NAVIGATION, ASSIGN CMPS,
C15 ASSIGN SRC/REC STATIC CORRECTIONS, BUTTERWORTH HIGHPASS FILTER (> 20 HZ),
C16 TRACE EDIT, DESPIKE, SPHERICAL DIVERGENCE CORRECTION, SET TRACE START TIME
C17 (3.5 S) AND LENGTH (2.4 S), NOISE REDUCTION (FX AND FK FILTERING), SRC
C18 WAVELET EXTRACTION, SRC DESIGNATURE TO ZERO PHASE (20-450 HZ BAND PASS),
C19 SRC/REC DEGHOST, NMO CORRECTION (1D VELOCITY MODEL), STACK, PHASE SHIFT
C20 TIME MIGRATION, TOP MUTE (WATER BOTTOM TIME - 10 MS), BOTTOM MUTE (TRACE
C21 END, 30 MS TAPER). INSERT DEAD TRACES FOR EMPTY CMPS (3-7 and 12511-12598).
C22
C23
C24 OUTPUT: 32-BIT IBM FLOATING POINT SEG-Y
C25 RECORD LENGTH: 2.4 SEC
C26 DELAY RECORDING TIME (3.5 S) IN BYTES 109-110
C27
C28 CDP COORDINATES ARE STORED IN GEOGRAPHIC ARCSECONDS (SCALED BY 100)
C29 DIVIDE BY 360000 FOR DECIMAL DEGREES.
C30 COORDINATE SCALAR IN BYTES 71-72
C31
C32 CDP-X AND CDP-Y IN BYTES 181-184 AND 185-188
C33 CDP NUMBER STORED IN BYTES 21-24
C34 TRACE ID IN BYTES 29-30 SET TO 2 FOR DEAD TRACES
C35
C36 FOR ADDITIONAL INFORMATION CONCERNING THIS DATASET REFER TO THE ASSOCIATED
C37 USGS SCIENCEBASE DATA RELEASE ONLINE AT:
C38 HTTPS://DOI.ORG/10.5066/P91WP1RZ
C39
C40

PROCESS STEP 3:
A python script (GEnavtoSQL.py) imported shot and CMP navigation from ASCII CSV files (produced in earlier processing steps) into a SpatiaLite (version 4.3.0) enabled SQLite (version 3.3.0) database, creating three tables containing point geometries. The first contained records for all shots by line, the second contained records of all CMPs by line, and the third maintained records for the first and last CMPs, and CMPs at multiples of 200 by line. A 200-CMP interval was chosen because it corresponds to the annotation and tick interval provided along the top of the migrated, stacked profile images. The resulting database columns for the shot table consists of East, North (WGS84 UTM18N m), Lon, Lat (WGS84 dd), LineName, FFID, Year, JD_UTC (DDD:HH:MM:SS), SurveyID, VehicleID, and DeviceID. The resulting database columns for the CMP tables consist of East, North (WGS84 UTM18N m), Lon, Lat (WGS84 dd), LineName, ImageName, CMP, Year, Fold, SurveyID, VehicleID, and DeviceID. A third table was created to contain trackline geometries generated from the CMP point geometries for each line (sorted by LineName and CMP), and the line length in kilometers was calculated. The resulting database columns of the line geometry table consist of LineName, ImageName, CMP_init, CMP_end, SurveyID, VehicleID, DeviceID, and Length_km.

PROCESS STEP 4:
The shot, CMP, and 200 CMP points, and CMP trackline features were added (Add Data) into ArcGIS Pro (version 2.3.3) from the SQLite database, then exported (using the Feature Class to Feature Class geoprocessing tool) to the new Esri point and polyline shapefiles '2018-002-FA_MCS_shtnav.shp', '2018-002-FA_MCS_cmpnav.shp', '2018-002-FA_MCS_cmp200.shp', and '2018-002-FA_MCS_cmpTracklines.shp', respectively. The Export Feature Attribute to ASCII geoprocessing tool was used to produce ASCII CSV files from the attribute tables of '2018-002-FA_MCS_shtnav.shp' and '2018-002-FA_MCS_cmpnav.shp'.

The Seismic Unix (version 4.3) script 'plot_geomet' was used to read the migrated, stacked SEG-Y files and create variable density greyscale Postscript plots (using the Seismic Unix 'psimage' module) showing two-way travel time (seconds) along the y-axis (left margin) and shots along profile (labeled at 1000 shot intervals) on the x-axis (along top of profile). The Postscript images were then converted to 300 dpi PNG formatted images using ImageMagick convert (version 6.9.10-78). The output PNF files were named according to filename convention with either '.v1d.pspstm.png' or '.v2d.srme.pspstm.png' appended to note the type of processing conducted.

Repaired some issues that the ScienceBase turn live process introduced - removed empty element (attribute accuracy report), in the distributions section added the additional links, access instructions, and additional distribution formats that had been deleted. Additionally, a typo in the abstract was fixed. Two distribution links were also updated to reflect the landing pages of the SEG-Y data.