Marine magnetics data collected by the U.S. Geological Survey in U.S. Atlantic Seaboard in 2014 (Geographic, WGS84, point shapefile 2014-011-FA_mag.shp)

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Frequently anticipated questions:

What does this data set describe?

Title:
Marine magnetics data collected by the U.S. Geological Survey in U.S. Atlantic Seaboard in 2014 (Geographic, WGS84, point shapefile 2014-011-FA_mag.shp)
Abstract:
In summer 2014, the U.S. Geological Survey conducted a 21-day geophysical program in deep water along the Atlantic continental margin by using R/V Marcus G. Langseth (Field Activity Number 2014-011-FA). The purpose of the seismic program was to collect multichannel seismic reflection and refraction data to determine sediment thickness. These data enable the United States to delineate its Extended Continental Shelf (ECS) along the Atlantic margin. The same data can also be used to understand large submarine landslides and therefore assess their potential tsunami hazard for infrastructure and communities living along the eastern seaboard. Supporting geophysical data were collected as marine magnetic data, gravity data, 3.5-kilohertz shallow seismic reflections, multibeam echo sounder bathymetry, and multibeam backscatter. 
The survey was conducted from water depths of approximately 1,500 meters to abyssal seafloor depths greater than 5,000 meters. Approximately 2,761 kilometers of multi-channel seismic data was collected along with 30 sonobuoy profiles.
This field program had two primary objectives: (1) to collect some of the data necessary to establish the outer limits of the U.S. Continental Shelf, or Extended Continental Shelf, as defined by Article 76 of the United Nations Convention of the Law of the Sea and (2) to study the sudden mass transport of sediments down the continental margin as submarine landslides that pose potential tsunamigenic hazards to the Atlantic and Caribbean coastal communities.
More information regarding the field activity can be found in the cruise report:
Supplemental_Information:
For more information on the field activity, see the field activity page https://cmgds.marine.usgs.gov/fan_info.php?fan=2014-011-FA
  1. How might this data set be cited?
    U.S. Geological Survey, 2017, Marine magnetics data collected by the U.S. Geological Survey in U.S. Atlantic Seaboard in 2014 (Geographic, WGS84, point shapefile 2014-011-FA_mag.shp): data release DOI:F7V69HHS, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    This is part of the following larger work.

    Arsenault, M.A., Miller, N.C., Hutchinson, D.R., Baldwin, W.E., Moore, E.M., Foster, D.S., O'Brien, T.F., and Fortin, W.F., 2017, Geophysical data collected along the Atlantic continental slope and rise 2014, U.S. Geological Survey Field Activity 2014-011-FA, cruise MGL1407: data release DOI:F7V69HHS, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    Suggested Citation:
    Arsenault, M.A., Miller, N.C., Hutchinson, D.R., Baldwin, W.E., Moore, E.M., Foster, D.S., O’Brien, T.F., and Fortin, W.F., 2017, Geophysical data collected along the Atlantic continental slope and rise 2014, U.S. Geological Survey Field Activity 2014-011-FA, cruise MGL1407: U.S. Geological Survey data release, https://doi.org/10.5066/F7V69HHS.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -76.085053
    East_Bounding_Coordinate: -65.769170
    North_Bounding_Coordinate: 39.630968
    South_Bounding_Coordinate: 30.677010
  3. What does it look like?
    https://cmgds.marine.usgs.gov/data/field-activity-data/2014-011-FA/data/geophysics/2014-011-FA_mag.jpg (JPEG)
    Image showing 1-minute averaged navigation data collected with marine magnetics data by the U.S. Geological Survey on the R/V Marcus G. Langseth, 2014
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 22-Aug-2014
    Ending_Date: 11-Sep-2014
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: vector digital data
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Vector data set. It contains the following vector data types (SDTS terminology):
      • Entity point (24697)
    2. What coordinate system is used to represent geographic features?
      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.0000001. Longitudes are given to the nearest 0.0000001. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is GCS_WGS_1984.
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257224.
  7. How does the data set describe geographic features?
    2014-011-FA_mag
    1-minute averaged navigation and marine magnetics data collected by the U.S. Geological Survey in U.S. Atlantic Seaboard in 2014 (Source: U.S. Geological Survey)
    FID
    Internal feature number (Source: Esri) Sequential unique whole numbers that are automatically generated.
    Shape
    Feature geometry (Source: Esri) Coordinates defining the features
    F_Longitud
    X-coordinate representing longitude location of magnetic measurement (geographic, WGS84) (Source: U.S. Geological Survey)
    Range of values
    Minimum:-76.085053
    Maximum:-65.769170
    Units:decimal degrees
    Resolution:0.000001
    Latitude
    Y-coordinate representing latitude location of magnetic measurement (geographic, WGS84) (Source: U.S. Geological Survey)
    Range of values
    Minimum:30.677010
    Maximum:39.630968
    Units:decimal degrees
    Resolution:0.000001
    DateTime
    Calendar date (year, month, day) and time of observation. This date and time is UTC in the format YYYY-MM-DDTHH:MM:SSZ where T indicates the end of the Year, month and day notation, and Z indicates that the time is 'Z' or UTC time. (Source: U.S. Geological Survey) text in the format YYYY-MM-DDTHH:MM:SSZ
    MagTotal_n
    Measured magnetic field intensity, in nanoteslas (nT) (Source: U.S. Geological Survey)
    Range of values
    Minimum:45710.53
    Maximum:51302.48
    Units:nanoteslas
    Resolution:0.01
    MagSignalL
    Measured magnetometer Signal Level in millivolts (Source: U.S. Geological Survey)
    Range of values
    Minimum:626.6
    Maximum:1559.7
    Units:millivolts
    Resolution:0.1
    MagDepth_m
    Depth of magnetometer below the sea surface based on depth transducer strain gauge. Units are millivolts, produced by the sensor in the magnetometer. (Source: U.S. Geological Survey)
    Range of values
    Minimum:254.1
    Maximum:3495
    Units:milivolts
    Resolution:0.1
    MagDepth_1
    Magnetometer depth below sea surface in meters, calculated from the millivolts measurement produced on the internal depth transducer strain gauge in the magnetometer (Source: U.S. Geological Survey)
    Range of values
    Minimum:2.5
    Maximum:55.3
    Units:meters
    Resolution:0.1
    IGRF_nT_
    International Geomagnetic Reference Field measurement in nanoteslas (nT). The International Geomagnetic Reference Field (IGRF) is a standard mathematical description of the large-scale structure of the Earth's main magnetic field and its secular variation. (Source: U.S. Geological Survey)
    Range of values
    Minimum:45820.9
    Maximum:51271.5
    Units:nanoteslas
    Resolution:0.1
    MagAnom_nT
    1-minute averaged magnetic anomaly in nanoteslas (nT). This is measured value (MagTotal_n) minus IGRF (IGRF_nT_) (Source: U.S. Geological Survey)
    Range of values
    Minimum:-2274.95
    Maximum:282.75
    Units:nanoteslas
    Resolution:0.01
    WDMAM_v1_1
    Values from the World Digital Magnetic Anomaly Map Grid (Source: U.S. Geological Survey)
    Range of values
    Minimum:-77.75
    Maximum:246.74
    Units:nanoteslas
    Resolution:0.01
    Entity_and_Attribute_Overview:
    The data are also available as a text file with the following columns headers: #Longitude Latitude DateTime MagTotal(nT) MagSignalLevel MagDepth(mV) MagDepth(m) IGRF(nT) MagAnom(nT) WDMAM v1.1(nT). These column headers correspond to the following shapefile attributes respectively: F_Longitud, Latitude, DateTime, MagTotal_n, MagSignalL, MagDepth_m, MagDepth_1, IGRF_NT, MagAnom_nT, WDMAM_v1.1.
    Entity_and_Attribute_Detail_Citation: none

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • U.S. Geological Survey
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    Nathan C. Miller
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, Massachusetts
    USA

    508-548-8700 x 2293 (voice)
    508-457-2310 (FAX)
    ncmiller@usgs.gov

Why was the data set created?

Marine magnetic data is used in conjunction with other geophysical data to map basement structure, and delineate magnetic structures. Magnetic data is useful in mapping structural trends, including intrusive features or faults that are often concealed under sedimentary cover. Magnetic survey data can be combined with previously collected magnetics data to produce total field contours, and support the identification of features within the seismic reflection data. This data was collected to support the seismic reflection data, and was collected as secondary/supporting data.

How was the data set created?

  1. From what previous works were the data drawn?
    none (source 1 of 1)
    U.S. Geological Survey, Unpublished Material, Marine Magnetics Data.

    Type_of_Source_Media: online
    Source_Contribution: Shipboard marine magnetics data
  2. How were the data generated, processed, and modified?
    Date: 2014 (process 1 of 8)
    The magnetometer was towed in the center of gravity position, 253 m behind the ship on the starboard side, without any additional weights added. When deployed, the tow cable is attached to a boom on the starboard side. The G-882 is equipped with a CM-221 counter module that converts the cesium Larmour signal (70 kHz to 350 kHz) into magnetic field strength in nanoteslas (nT). The G-882 is a cesium vapor magnetometer, with a sensitivity to <0.004 nT/ Hz root-mean-square, an accuracy of <3 nT, and an operating range of 20,000 to 100,000 nT. Situated at the tail of the tow-fish, the magnetometer sensor should be oriented so that the Earth’s magnetic field lines are centered in the sensor’s active zone. For MGL1407, the sensor was oriented in the vertical configuration which is optimal for mid-magnetic latitudes (magnetic inclination > 67.5 degrees). Person who carried out this activity:
    Matthew A. Arsenault
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, Massachusetts
    USA

    508-548-8700 x2354 (voice)
    508-457-2310 (FAX)
    marsenault@usgs.gov
    Date: 2014 (process 2 of 8)
    During the survey, magnetometer data were logged 10 samples per second and recorded into raw data files, containing the magnetometer measurements, a date and time stamp, and sensor status. The raw data files are text files containing the samples for a 24-hour period based on Julian Day (JD, UTC time). The data streams are combined with a time stamp from NTP server aboard Langseth, which synchronizes time from the ship’s Global Positioning Satellite (GPS) clock. Person who carried out this activity:
    Matthew A. Arsenault
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, Massachusetts
    USA

    508-548-8700 x2354 (voice)
    508-457-2310 (FAX)
    marsenault@usgs.gov
    Date: 2014 (process 3 of 8)
    Raw data were downloaded at the completion of each day of measurements and transferred to a Linux laptop that was specially set-up with C-shell scripts for field processing the data. Person who carried out this activity:
    Matthew A. Arsenault
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, Massachusetts
    USA

    508-548-8700 x2354 (voice)
    508-457-2310 (FAX)
    marsenault@usgs.gov
    Date: 2014 (process 4 of 8)
    A series of C-shell scripts, written by Daniel Scheirer of the USGS (Menlo Park) were used to process the data: run_anverage_mag01: to create 1 minute averages of Langseth magnetics data. Magnetics values are merged with navigation in this script, IGRF corrections were applied, and Magnetic anomalies (total measured magnetic field minus IGRF fieldto derive MagAnom) were calculated. Values from the World Digital Magnetic Anomaly Map Grid (WDMAM, Maus and others, 2007) were sampled at each shipboard observation point for comparison with the measured magnetic anomalies (results in WDMAM v1.1). run_average_bath02: creates 1-minute averages of centerbeam depth. Plot_daily_mag01_new: creates a multi-panel plot with 1-minute averaged magnetic anomaly against the WDMAM grid, centerbeam depth, and sensor signal level from daily cruise data. This script was modified mid-cruise to include a panel displaying the magnetometer signal level, and the estimated magnetometer depth. A description of this calculation can be found in the G-882 owners manual listed in the cross reference section of this metadata file (Geometrics, Inc., 2005). plot_map: plots maps showing cumulative track for the cruise superimposed on ETOPO1 bathymetry, satellite-altimetry-derived gravity grid (Sandwell and Smith, 2009), WDMAM grid, and a blank background. run_create_info_files: generates an informational summary file of the data and plots. This script generates a text file made of the first and last 10 lines of each daily data file. The output was used for troubleshooting and quality assurance while on the ship.
    A summary (text) file was written from the above processing stream. The first 4 lines of the output file are:
    #Longitude Latitude DateTime MagTotal(nT) MagSignalLevel MagDepth(mV) MagDepth(m) IGRF(nT) MagAnom(nT) WDMAM_v1.1(nT) -72.761622 39.630968 2014-08-22T06:34:00Z 51257.74 1042.2 0824.9 11.8 51271.50 -13.76 18.02 -72.759143 39.628698 2014-08-22T06:35:00Z 51255.40 1163.4 0825.7 11.8 51269.90 -14.50 17.10 -72.756638 39.626415 2014-08-22T06:36:00Z 51253.87 1390.4 0808.6 11.5 51268.20 -14.33 16.17 Person who carried out this activity:
    Matthew A. Arsenault
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, Massachusetts
    USA

    508-548-8700 x2354 (voice)
    508-457-2310 (FAX)
    marsenault@usgs.gov
    Date: 2017 (process 5 of 8)
    The 1 minute averaged navigation was downloaded (post-cruise) from the Rolling Deck to Repositry (R2R) website (Lamont-Doherty Earth Observatory, 2014), and merged using a C-shell script, run_merge_r2rnav_gravmag, provided by Daniel Scheirer of the USGS.
    The R2R 1-minute navigation does not always have time-stamps at the even minute mark; occasionally a record appears where the seconds value equals 01 or 59. This makes the merging with the 1-minute geophysical records difficult, and that is why the navigation is fixed using routines within the C-shell script.
    The output is a text file, which is provided with this data release. Person who carried out this activity:
    Matthew A. Arsenault
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, Massachusetts
    USA

    508-548-8700 x2354 (voice)
    508-457-2310 (FAX)
    marsenault@usgs.gov
    Date: 2017 (process 6 of 8)
    The 1 minute average of Langseth magnetics data file was imported into Esri ArcMap 10.3 using ArcCatalog, Create Feature Class from XY Table, specifying geographic coordinates, WGS84 coordinate system (EPSG code 4326). The point shapefile was visually inspected for problems with the data points. None were identified, so the data was believed complete. Person who carried out this activity:
    Matthew A. Arsenault
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, Massachusetts
    USA

    508-548-8700 x2354 (voice)
    508-457-2310 (FAX)
    marsenault@usgs.gov
    Date: 02-Apr-2018 (process 7 of 8)
    An error was fixed in one of the originator names. Also fixed in the suggested citation. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@usgs.gov
    Date: 08-Sep-2020 (process 8 of 8)
    Added keywords section with USGS persistent identifier as theme keyword. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@usgs.gov
  3. What similar or related data should the user be aware of?
    Maus, S., Sazonova, T., Hemant, K., Fairhead, J.D., and Ravat, Dhananjay, 2007, National Geophysical Data Center candidate for the World Digital Magnetic Anomaly Map: Geochemistry Geophysics Geosystems: An Electronic Journal of the Earth Sciences v. 8, no. 6, American Geophysical Union, Washington, D.C..

    Online Links:

    Geometrics, Inc., 2005, G-882 Cesium Marine Magnetometer 25919-OM REV. F Operation Manual: Geometrics, Inc., San Jose, CA.

    Online Links:

    Observatory, Lamont-Doherty Earth, 2014, Rolling Deck to Repository (R2R): UNCLOS, UNCLOS.

    Online Links:

    Other_Citation_Details:
    Standard data products listed on the Rolling Deck to Repository website include cruise level metadata with an expedition summary including cruise id, vessel, operator, project titles and funding awards, science party, ports, dates, survey targets, and trackline geometry. There is also quality-controlled shiptrack navigation, and scientific sampling event logs. Some post-processed geophysical trackline profiles (underway gravity, magnetics, bathymetry, etc), for vessels equipped with these instrument types; and hydrographic profiles (depth, temperature, salinity, etc from CTD).

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
    Daily shipboard processing was done to ensure quality control over the data. Daily data was downloaded and plotted, then assessed as an indicator of proper magnetometer function. These steps are further outlined in the process steps.
  2. How accurate are the geographic locations?
    Navigation was acquired using the R/V Marcus G. Langseth's Network Time Protocol (NTP) server which synchronizes to the ship’s GPS clock. The magnetometer was towed in the center of gravity configuration, 253 m behind the ship on the starboard side, so a 253 m layback was applied. The horizontal accuracy is assumed to be 10 meters.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    This dataset represents all of the data collected during the MGL1407 cruise. While data collection was periodically interrupted for weather and safety considerations, the data listed here is represents what was collected. For an overview of the data interruptions, please see the logical consistency report.
  5. How consistent are the relationships among the observations, including topology?
    Under normal data collection conditions, the magnetometer is deployed and remains deployed until the end of data collection. Magnetic data collection had interruptions and data gaps during the MGL1407 cruise, mostly because the magnetometer needed to be recovered during the deployment and recovery of seismic equipment, which happened multiple times on the cruise (initial deployment on Julian Day JD235, passage of hurricane Cristobal on Julian Day JD238, and a medevac on Julian Day JD241). The data coincide with all seismic lines, as well as additional tracks that include a test segment prior to the start of seismic acquisition (Julian Day JD234), and tracks laid out to avoid hurricane Cristobal.
    Three calibration loops were conducted on August 28, 2014 (Julian day JD240) to test the consistency of magnetometer readings at the loop crossings. The loop pattern was started at 10:24 UTC and finished at 11:23 UTC, resulting in four points of crossing. During the daily review of the magnetometer data, noise was observed in the 1-minute smoothed data plots from JD 246 starting at approximately 21:00 UTC (JD 246.8). At 14:30 on JD 247 the G-882 was powered down and retrieved to check all connectors and cables. As the G-882 neared the boat, a large collection of seaweed was visible on the tow cable where it meets the G-882. The seaweed was cleared, and the G-882 was brought on deck. Upon opening the nose assembly, a white, granular precipitate was seen on the protective housing to the male/female 8-pin connector. The precipitate was cleared and the male and female connectors separated for inspection. The pins were cleaned with a wire brush, and some dialectic grease applied to the connection. The nose assembly was returned to its original state, with the G-882 set in the CG tow position and the unit was redeployed to 220 m behind the ship. During MGL1407, the magnetometer displayed low signal levels. These low signals may have been caused by the connector corrosion (north of latitude 36o) or sub-optimal sensor positioning relative to the Earth’s magnetic field vector. Many of these noisy and low sensor values coincide with the ship course of 230-240 degree azimuth. They can be noted at JD 246 04:00 and JD 248 02:30. On JD 254 when seismic data collection ended and the G-882 was brought on board for the last time, more white precipitate was on the outside of the connector housing.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: None
Use_Constraints:
Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey as the originator of the dataset.
  1. Who distributes the data set? (Distributor 1 of 1)
    Nathan C. Miller
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, Massachusetts
    USA

    508-548-8700 x2293 (voice)
    508-457-2310 (FAX)
    ncmiller@usgs.gov
  2. What's the catalog number I need to order this data set? USGS data release 2014-011-FA magnetics data from the Atlantic Ocean (2014-011-FA_mag.zip). The compressed file contains an ascii text file: 2014-011-FA_mag.txt, an Esri formatted vector shapefile in geographic coordinates (2014-011-FA_mag.shp and other shapefile components), a mapview image of the data (2014-011-FA_mag.jpg), a PDF file of the daily data plots (MGL1407_Magnetics_Daily_Plots.pdf), and Federal Geographic Data Committee (FGDC) Content Standards for Digital Geospatial Metadata (CSDGM) metadata files in xml, txt and html formats are also included in the compressed file.
  3. What legal disclaimers am I supposed to read?
    Neither the U.S. Government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  4. How can I download or order the data?
  5. What hardware or software do I need in order to use the data set?
    This compressed file contains data available in Esri shapefile format, space-delimited text files, and PDF plots. The compressed file also contains associated metadata. The user must have software to read and process the data file.

Who wrote the metadata?

Dates:
Last modified: 08-Sep-2020
Metadata author:
Matthew A. Arsenault
U.S. Geological Survey
Geologist
384 Woods Hole Road
Woods Hole, Massachusetts
USA

508-548-8700 x2354 (voice)
508-457-2310 (FAX)
marsenault@usgs.gov
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/whcmsc/field_activities/2014_011_fa/2014-011-FA_mag_meta.faq.html>
Generated by mp version 2.9.50 on Tue Sep 21 18:20:15 2021