Quality control was conducted during processing to ensure consistency of stacked CMP SEG-Y data files with corresponding navigation ASCII CSV and shapefiles and seismic profile images. CMP numbers and navigation are consistent between corresponding surveylines in '2019-002-FA_MCS_psmig_segy.zip', '2019-002-FA_*MCS_Images.zip', '2019-002-FA_MCS_cmp500.shp', '2019-002-FA_MCS_cmpnav.csv', and '2019-002-FA_MCS_cmpTracklines.shp'. The attribute fields 'LineName' and 'ImageName' for each polyline feature in '2019-002-FA_MCS_cmpTracklines.shp' correspond to the SEG-Y data files in '2019-002-FA_MCS_psmig_stack_segy.zip' and the PNG profile images in '2019-002-FA_MCS_Images.zip', respectively.
The shot navigation file '2019-002-FA_MCS_shotnav.csv' contains navigation coordinates for all shot records acquired during the survey except for L1F1 and L1F2, because there was no navigation recorded in the SEG-D files. This portion of Line 1 was reshot (Line 39) later in the survey. There is no L14F1 recorded due to misfiring. Data were collected intermittently between August 1, 2019 and August 28, 2019. Additionally, one line (2019-014-FA_L1F1) collected on May 23, 2019 aboard the R/V Rafael during the pre-cruise testing field activity FA-2019-014 is included in the dataset. No multichannel seismic data were recorded during transits to and from ports and the MCS equipment was not always deployed mostly because of restricted maneuverability around fishing gear, particularly during nighttime operations. Increased turning time would have impacted time to acquire high priority bathymetry coverage. MCS line names did not always coincide with lines that only recorded chirp subbottom and multibeam sonar. Every shot record may not contain active reflection data if the source was not being fired. The S-Boom stopped firing on Line 9, JD 214 from 2313 and 2319, due to an encounter with a whale. Shots 6375 to 6780 on Line 19 were missed due to a triggering malfunction. One MCS test line was shot on May 23, 2019 and these data are included with this release. The line name is 2019-014-FA_L1F1. The Vessel ID is R/V Rafael.
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
Multichannel seismic-reflection shots were navigated using an Ashtech ProFlex 800 or Hemisphere R131 Differential GPS (DGPS) receiver, both with the same navigational reference point (NRP) antenna mounted aft end and on top of the acquisition van. The NRP was offset a few meters port of the vessel centerline, approximately between the centerline of the towed source (S-Boom) and the streamer that was towed from the port quarter of the vessel. The S-Boom was towed 25.8 m astern of the NRP along the centerline of the vessel, and the GeoEel streamer (50 m active section) was towed from a boom on the port quarter with the center of the first (channel 1) and last (channel 32) active groups trailing the NRP by 42.9 m and 92.24 m respectively. The Geometrics CNT-1 seismic acquisition software (version 5.64) logged the shot navigation coordinates to the SEG-D external header. Processing descriptions provided below outline the procedures for calculating layback distances between the NRP, acoustic source, and receivers and the Common Midpoint (CMP) binning process. Although horizontal accuracy of WAAS enabled DGPS is estimated to be within 2-3 m, we assume the accuracy of the shot positions to be +/- 10 m due to layback offset between the NRP and far offsets of the receivers (there was no tail buoy with GPS) and movement of the source astern of the ship. Accuracy of CMP bin location is assumed to be coarser due to the additional uncertainty added from calculation of source/receiver layback and common midpoint positions.The test line shot May 23, 2019 used the GeoEel streamer with a single plate Applied Acoustics AA251 boomer. The boomer and streamer were towed from the R/V Rafael. A Hemisphere DGPS receivers was used. Positional accuracy is the same as described above. Offsets from the navigation reference point (NRP) to the source and receivers were different, which are described in the process steps.
Vertical_Positional_Accuracy:
Vertical_Positional_Accuracy_Report:
Streamer mounted RBR Solo-D depth loggers estimated receiver depths with the RBR Ltd. Ruskin utility (v2.7.3.201905031233) via the simplified derivation, where depth in meters = (measured pressure in dbar - atmospheric pressure (set to default 10.1325 dbar)) / (density (set to default 1.0281 g/mL) * 0.980665). The RBR Solo-D units used are rated to 20 meters and RBR Ltd. state that they are accurate to +/- 0.05 percent of full scale (about 1 cm water depth).
Source_Information:
Source_Citation:
Citation_Information:
Originator: U.S. Geological Survey
Publication_Date: Unpublished Material
Title: Raw MCS data
Geospatial_Data_Presentation_Form: binary digital data
Type_of_Source_Media: disc
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20190523
Ending_Date: 20190828
Source_Currentness_Reference:
ground condition, one line collected in May 2019, the rest during Aug 2019
Source_Citation_Abbreviation: MCS data
Source_Contribution:
Multichannel seismic-reflection data were shot using a triple plate boomer, Applied Acoustics S-Boom powered by an Applied Acoustics CPS-D power supply that was set to a total power output of 400 Joules. Line 2019-014-FA_L1F1 collected on May 23, used an Applied Acoustics AA251 single-plate boomer powered by an Applied Acoustics CPS-D power supply with a total power output of 200 Joules. The S-Boom has three boomer plates mounted to a surface towed catamaran that was towed 25.8 m astern of the NRP along the centerline of the M/V Warren Jr. On May 23, the single-plate Applied Acoustics AA251 was mounted on a catamaran and towed 8 meters aft of the starboard quarter of the R/V Rafael. The source was typically triggered on distance (3.2 m intervals) using the USGS developed RasperryPi and Python based TriggerPi controller, but also occasionally on time (equating to similar shot distances) using the Geometric CNT-1 software. Shots were recorded using a Geometrics GeoEel digital streamer composed of four 12.5 m solid state active sections (a total of 32 channel groups with 1.5625- spacing) connected to a Geometrics Streamer Power Supply Unit (SPSU). The first and last active groups trailed the NRP by 42.9 m and 92.24 m (or 24.8 m and 74.1 m on the R/V Rafael on May 23), respectively. A 10 m isolation section was positioned before the active sections to reduce the impacts of ship tug. Five RBR Ltd. RBRsolo D depth loggers were also spaced along the steamer to record depth data. Geometrics CNT-1 seismic acquisition software (version 5.64) running on a Windows PC was used to control the multichannel system, digitally log traces in the Geometrics SEG-D format, and record shot NRP GPS navigation coordinates to the SEG-D external headers. Raw records were recorded over trace lengths of 250 milliseconds, with sample intervals of 63 microseconds
Process_Step:
Process_Description:
PROCESS STEP 1:
Shearwater Reveal (version 2019) and Kingdom Suite (ver. 2017) seismic processing software was used to execute the following processing flows to produce the stacked SEG-Y files processed through post-stack time migration.
(1.) Import SEG-D sequences: SegDRead read raw Geometrics SEG-D shot sequence MCS files, extracted navigation fixes from the external headers, and wrote them to new header words, 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 19N WGS 84 meters (NRP_X, and NRP_Y). Output wrote the trace sequence to Reveal formatted ".seis" files.
(2.) 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 navigation reference point (NRP) to the center of the sources (cos) and the centers of the first and last 1.5625 m spaced channel groups. The following lists the linear offsets from the NRP to center of source (COS) and index channels (IC) used to define layback geometry. NRP to COS, NRP to IC offset(IC#)2019-002-FA M/V Warren Jr: -25.8,-42.9(1)/-92.24(32)2019-014-FA R/V Rafael: -10.7, -24.8(1)/-74.1(32)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). CMP bin spacing was set to 0.8 m, the first cmp to 1, and computed CMP coordinates (BIN_X and BIN_Y). Output wrote the trace sequence with defined geometry (offset and CMP) to new files.
(3.) DBWrite wrote the layback geometry source positions (in UTM 19N 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. An issue with the Reveal implementation of UTMtoLatLon causes offsets of up to 5-cm (but generally 2-3 or less) between the output geographic and UTM values for the CMPs.
(4.) 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 0.5 m (position of the three boomer plates on the S-Boom catamaran), then converted both static values from meters to milliseconds (dividing by an assumed water column sound speed velocity of 1.51 m/ms) and wrote them to new header words. The source/receiver static values were then applied to the traces. Static corrections using the depth loggers successfully compensates for vertical movement of the streamer. Lines 3 and 32 showed static offsets after applying pressure depth corrections, most likely due to horizontal movement of the streamer. A method of flattening both horizontal and vertical movement was applied by digitizing the direct source to receiver arrival in Kingdom Suite (ver. 2017) and converting one-way travel time to two-way travel time. A mean value of the two-way travel time for the entire line was used to calculate a difference between the mean and the two-way travel times. This difference was merged with seismic traces in Reveal using FFID and channel and a static shift was applied and written to new files.
(5.) 2D velocities were picked using an interactive Reveal semblance picking flow. Input read the static corrected 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 1510 m/s. Final picks were saved to Reveal database tables by line. The 2D velocity model was subsequently used in SRME, NMO, and poststack migration processes.
(6.) Surface related multiple elimination (SRME) was applied in Reveal to the static corrected trace files. SRMEPrepOffsets inserted place-holder dead traces in the shot domain so that traces were extended to zero offset. SRMENearExtrap extrapolated amplitudes to near the offset traces inserted in the previous step using tau-p in the CMP domain. Mute applied a top mute to all traces just prior to the sea floor time to remove the direct arrival. 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 static corrected and predicted multiple files in two parallel branches. SRMESubtract performed shot by shot comparison of the static corrected and predicted multiple traces to produce refined filtered multiple operators that were passed along to a second SRMESubtract process which subtracted (adaptive subtraction) the refined predicted multiple energy from the static corrected data. Output wrote the static corrected and multiple-reduced data to new files.
(7.) Processed stack: Input read the static corrected and multiple-reduced files sorted to CMP, NormalMoveout converted traces to zero offset using the 2D velocity model created for each file, Stack produced a single trace per CMP bin. A time raised power gain was applied (T**PWR * EXP(BETA*T) with PWR=0.5, BETA=0, T=two-way travel time, start time=0 ms, end time=150 ms Output wrote the stacked traces to new files.
(8.) Post-stack time migration: Input read the stacked files, PostStackMigration performed a phase-shift time migration using the 2D velocity model created for each file (1700 Hz maximum frequency and 0.8 m bin spacing), and Output wrote the migrated stacked traces to new files.
(9.) SEG-Y output: Input read the migrated stacked files. HeaderMath 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 19N WGS84 meters and geographic decimal degrees), CMP number and year to ASCII CSV text files by line. Output wrote the migrated, stacked traces to SEG-Y Rev. 1 format (32-Bit IEEE floating point). Each output SEG-Y file contains a textural file header similar to the example from line 2019-002-FA_L1F3.psmig.sgy included below. Example migrated stacked file SEG-Y Textural File Header:C 1 U.S. GEOLOGICAL SURVEY WOODS HOLE COASTAL AND MARINE SCIENCE CENTERC 2 SURVEY_ID: 2019-002-FA AREA: CAPE COD BAY VESSEL: M/V WARREN JR.C 3 YEAR: 2019 LINENAME: L1F3C 4C 5 ACQUISITION: APPLIED ACOUSTICS S-BOOM, 3.25 METER SHOT INTERVAL,C 6 32 CHANNEL GEOMETRICS GEOEEL HYDROPHONE STREAMER (1.5625 METER GROUPS),C 7 0.063 MS RECORDING SAMPLE INTERVAL, 0.25 SEC RECORD LENGTH, RECORDEDC 8 IN SEG-D FORMAT.C 9C10C11C12 PROCESSING: IMPORT SEG-D SEQUENCE FILE,USING NRP NAVIGATION ASSIGNC13 SRC/REC/MIDPOINT GEOMETRY, ASSIGN CMPS, ASSIGN SRC/REC STATICC14 CORRECTIONS, APPLY SRME SPHERICAL DIVERGENCE CORRECTION, BANDPASSC15 FILTER 200-300-1650-1800, NMO CORRECTION (2D VELOCITY MODEL,C16 GAIN: TIME^1.25, STACK, PHASE SHIFT TIME MIGRATION, EXPORT SEG-YC17C18C19C20C21C22C23C24 OUTPUT: 32-BIT IEEE FLOATING POINT SEG-YC25 RECORD LENGTH: 0.25 SECC26C27C28 CDP COORDINATES ARE STORED IN GEOGRAPHIC ARCSECONDS (SCALED BY 100)C29 DIVIDE BY 360000 FOR DECIMAL DEGREES.C30 COORDINATE SCALAR IN BYTES 71-72C31C32 CDP-X AND CDP-Y IN BYTES 181-184 AND 185-188C33 CDP NUMBER STORED IN BYTES 21-24C34C35C36 FOR ADDITIONAL INFORMATION CONCERNING THIS DATASET REFER TO THE ASSOCIATEDC37 USGS SCIENCEBASE DATA RELEASE ONLINE AT:C38 HTTPS://DOI.ORG/XXXX/XXXXC39C40 Shipboard and post-cruise processing were also conducted by David Foster.
Process_Date: 2019
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Person: David S. Foster
Contact_Position: Geologist
Contact_Address:
Address_Type: Mailing and Physical
Address: 384 Woods Hole Rd.
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543-1598
Contact_Voice_Telephone: (508) 548-8700 x2271
Contact_Facsimile_Telephone: (508) 457-2310
Contact_Electronic_Mail_Address: dfoster@usgs.gov
Process_Step:
Process_Description:
PROCESS STEP 2:
(1.) An AWK script was used to read the concatenated shot navigation CSV files for each line and populate a new attribute column for LineName. Excel was used to add attribute columns for SurveyID, VehicleID, and Device ID. The resulting columns for the shot table in file '2019-002-FA_MCS_shotnav.csv' consists of East, North (WGS84 UTM19N m), Lon, Lat (WGS84 dd), LineName, FFID, Year, JD_UTC, SurveyID, VehicleID, and DeviceID.
(2.) An AWK script was used to read the concatenated CMP navigation CSV files for each line and populate new attribute columns for LineName and ImageName. Excel was used to add attribute columns for SurveyID, VehicleID, and Device ID. An AWK script was used to extract first and last CMP values and multiples 500 CMPs for each line. A 500-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 UTM19N m), Lon, Lat (WGS84 dd), LineName, CMP, Year, SurveyID, VehicleID, and DeviceID.
(3.) A Python script MCStoSQL_19002.py was to import the CMP CSV files to a Spatialite (version 4.3.0) enabled SQLite (version 3.21.0) database, creating three tables containing point and polyline geometries for the unique and 500 CMP navigation and trackline features. The resulting database columns for the CMP tables consist of East, North (WGS84 UTM19N m), Lon, Lat (WGS84 dd), LineName, ImageName, CMP, Year, 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_Date: 202006
Process_Step:
Process_Description:
PROCESS STEP 3:
The CMP points, 500 CMP points, CMP tracklines were added (Add Data) into ArcGIS Pro (version 2.4.1) from the SQLite database, then exported (using the Feature Class to Feature Class geoprocessing tool) to the new Esri point and polyline shapefiles '2019-002-FA_MCS_cmpnav.shp', '2019-002-FA_MCS_cmp500', and '2019-002-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 '2019-002-FA_MCS_cmpnav.shp'.
Process_Date: 202006
Process_Step:
Process_Description:
PROCESS STEP 4:
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 500 CMP 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 PNG files were named according to filename convention with '.psmig.png', psmig (post-stack migration) was the final process applied.
Process_Date: 20220119
