Landslides offshore of southern California, 2023

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Frequently anticipated questions:

What does this data set describe?

Title: Landslides offshore of southern California, 2023
Abstract:
Landslides have been mapped offshore of Southern California. Polygons were mapped from visual interpretation of high-resolution multibeam echosounder data (MBES), single-beam echosounder data, and seismic reflection data.
Supplemental_Information:
Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this Federal Geographic Data Committee-compliant metadata file is intended to document the data set in nonproprietary form, as well as in Esri format, this metadata file may include some Esri-specific terminology.
  1. How might this data set be cited?
    Papesh, Antoinette G., Walton, Maureen L., Conrad, James E., Brothers, Daniel S., Kluesner, Jared W., and McGann, Mary L., 20230821, Landslides offshore of southern California, 2023: data release DOI:10.5066/P9IIWTYL, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.

    Online Links:

    This is part of the following larger work.

    Papesh, Antoinette G., Walton, Maureen L., Conrad, James E., Brothers, Daniel S., Kluesner, Jared W., and McGann, Mary L., 2023, Digital maps of submarine landslides and mass wasting features offshore of southern California, 2023: data release DOI:10.5066/P9IIWTYL, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -120.913005
    East_Bounding_Coordinate: -117.311194
    North_Bounding_Coordinate: 34.518320
    South_Bounding_Coordinate: 32.425737
  3. What does it look like?
    landslides_offshore_socal_2023_thumb.png (PNG)
    Southern California location map with bathymetry and mapped discrete landslides
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 1998
    Ending_Date: 30-Jul-2021
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: polygon shapefile
  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):
      • GT-polygon composed of chains (63)
    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 0.0001. Longitudes are given to the nearest 0.0001. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is D_WGS_1984.
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257223563.
      Vertical_Coordinate_System_Definition:
      Depth_System_Definition:
      Depth_Datum_Name: North American Vertical Datum of 1988
      Depth_Resolution: 1.0
      Depth_Distance_Units: meters
      Depth_Encoding_Method: Explicit depth coordinate included with horizontal coordinates
  7. How does the data set describe geographic features?
    landslides_offshore_socal_2023
    polygons representing mapped landslides (Source: U.S. Geological Survey)
    FID
    internal feature number (Source: Esri) automatically generated sequential unique whole number identifier
    Shape
    feature geometry (Source: Esri) feature type
    name_id
    the name of the landslide (Source: U.S. Geological Survey and California Geological Survey) The name of the landslide as commonly reported in peer-reviewed publications or a unique shortform abbreviated name based on landslide location. Attribute values match those in the name_id attribute for landslide_evac_zones_2023.shp and landslide_debris_aprons_2023.shp, available elsewhere in this data release. We define prefixes as follows: CB is Catalina Basin; CI is Catalina Island; GSC is Gulf of Santa Catalina; PA is Point Arguello; SBB is Santa Barbara Basin; SClB is San Clemente Basin; SCB is Santa Cruz Basin; SDT is San Diego Trough; SG is San Gabriel; SNB is San Nicolas Basin; SPB is San Pedro Basin.
    location
    the geographic location of the landslide (Source: U.S. Geological Survey and California Geological Survey) The commonly reported geographic location of the landslide
    lat_dd
    centroid coordinate latitude (Source: Esri)
    Range of values
    Minimum:32.48469
    Maximum:34.50649
    Units:degrees
    Resolution:0.000001
    long_dd
    centroid coordinate longitude (Source: Esri)
    Range of values
    Minimum:-120.808261
    Maximum:-117.374616
    Units:degrees
    Resolution:0.000001
    area_m2
    Area of the landslide including both evacuation zone and debris apron. Values are reported in square meters; uncertainly values may be found in the area_err attribute. (Source: Esri)
    Range of values
    Minimum:25646
    Maximum:232290744
    Units:square meters
    Resolution:1
    area_err
    Estimated uncertainty from data resolution and user interpretation, values in square meters. GIS-calculated area was approximated as a circle geometry with radius uncertainty of plus or minus 50 meters and plus or minus 20 meters for areas greater and less than 100,000 square meters, respectively. These values are based on 2 pixels of the likely resolution of bathymetric data used for mapping (25-meter and 10-meter resolutions). The calculated error is the standard deviation of the maximum, minimum, and picked geometries. (Source: U.S. Geological Survey)
    Range of values
    Minimum:11377
    Maximum:2699725
    Units:square meters
    Resolution:1
    total_len_m
    The maximum runout length from headwall scarp to the end of landslide debris approximated by hand using a GIS ruler tool; values reported in meters (Source: U.S. Geological Survey)
    Range of values
    Minimum:204
    Maximum:32616
    Units:meters
    Resolution:1
    scarp_ht_m
    a hand measurement of the landslide headwall scarp height in meters; see the scp_ht_err attribute for uncertainty (Source: Esri)
    Range of values
    Minimum:1
    Maximum:200
    Units:meters
    Resolution:1
    scp_ht_err
    estimated uncertainty of the landslide headwall scarp height measurement, see scarp_ht_m, in meters (Source: Esri)
    Range of values
    Minimum:1
    Maximum:40
    Units:meters
    Resolution:1
    vol_wdg_m3
    the volume of displaced sediment calculated using the corresponding evacuation zone area (evaczones_offshore_socal_2023.shp, found elsewhere in this data release) and approximating a wedge geometry using the measured headwall height (see scarp_ht_m attribute). The formula used is 1/2 times evacuation zone area times scarp height, in cubic meters. See vol_pcterr for uncertainty. (Source: U.S. Geological Survey)
    Range of values
    Minimum:23847
    Maximum:8854292904
    Units:cubic meters
    Resolution:1
    vol_pcterr
    Estimated volume percent uncertainty from evacuation zone area (area_err attribute found in evaczone_offshore_socal_2023.shp and headwall height (see scarp_ht_m attribute) used for the volume calculation (see vol_wdg_m3_attribute). Area uncertainty (also found in the evaczone_offshore_socal_2023.shp shapefile) was calculated by propagating error in evacuation zone uncertainty (area_err) and headwall scarp height uncertainty (scp_ht_err attribute) to determine total percent volume uncertainty. (Source: U.S. Geological Survey)
    Range of values
    Minimum:14
    Maximum:108
    Units:percent
    Resolution:1
    slope_deg
    Mean slope approximation of the landslide failure plane in degrees. Determined from the mean of slope picks taken by 3 different analysts from underlying 30-m resolution (or the 90-m resolution NCEI Coastal Relief Model (National Geophysical Data Center, 2012, if 30-m resolution data was unavailable) bathymetric slope data; outliers were removed for mean calculations; values reported in degrees (Source: U.S. Geological Survey and California Geological Survey)
    Range of values
    Minimum:0.6
    Maximum:36.8
    Units:degrees
    Resolution:0.1
    slope_err
    calculated slope uncertainty, reported as the standard deviation of slope grid picks from the slope_deg attribute; values reported in degrees (Source: U.S. Geological Survey and California Geological Survey)
    Range of values
    Minimum:0
    Maximum:4.4
    Units:degrees
    Resolution:0.1
    grad_pct
    gradient percentage calculated from the slope_deg attribute value using tan (slope_deg)*100; values reported as percentage (Source: U.S. Geological Survey and California Geological Survey)
    Range of values
    Minimum:1
    Maximum:75
    Units:percent
    Resolution:1
    dep_min_m
    the minimum depth below sea level of the landslide determined from the GIS calculated value of the minimum depth of the landslide from the NCEI coastal relief model (National Geophysical Data Center, 2012); values reported in meters (Source: Esri)
    Range of values
    Minimum:9
    Maximum:1409
    Units:meters
    Resolution:1
    dep_max_m
    the maximum depth below sea level of the landslide determined from the GIS calculated value of the maximum depth of the landslide from the NCEI coastal relief model (National Geophysical Data Center, 2012); values reported in meters (Source: Esri)
    Range of values
    Minimum:49
    Maximum:2619
    Units:meters
    Resolution:1
    prox_coast
    the landslide proximity to the coastline determined from the GIS calculated value of the minimum distance in meters between the landslide evacuation zone and the coastline from the NCEI coastal relief model (National Geophysical Data Center, 2012) (Source: Esri)
    Range of values
    Minimum:0
    Maximum:44165
    Units:meters
    Resolution:1
    prox_130m
    the landslide proximity to the 130 meter depth contour determined from the GIS calculated value of the minimum distance in meters between the landslide evacuation zone and the 130 meter depth contour derived from the NCEI coastal relief model (National Geophysical Data Center, 2012) (Source: Esri)
    Range of values
    Minimum:0
    Maximum:29002
    Units:meters
    Resolution:1
    prox_qflts
    the landslide proximity to quaternary faults calculated from the GIS calculated value of the distance in meters between the landslide evacuation zone and faults in the Quaternary Faults Offshore of California compilation by Walton and others, 2020 (Source: Esri)
    Range of values
    Minimum:0
    Maximum:48340
    Units:meters
    Resolution:1
    data_type
    a list of primary data types used for landslide mapping, categorized as bathymetry (with resolution in parentheses), seismic reflection (Source: U.S. Geological Survey and California Geological Survey) data type may be appended with its resolution information in parentheses
    slide_type
    following USGS landslide type identification according to USGS fact sheet 2004-3072 (USGS, 2004), categorized as: debris avalanche, earth flow, rotational, translational (Source: U.S. Geological Survey)
    ValueDefinition
    debris avalanchesource areas often associated with steep gullies and usually indicated by the presence of a debris field containing blocky material, often indicating rapid debris flow.
    earth flowa slide consisting of unconsolidated surficial material, typically with a characteristic hourglass geometry
    rotationala slide in which the surface of rupture is curved concavely upward, and the slide movement is roughly rotational about an axis that is parallel to the ground surface and transverse across the slide
    translationala slide in which mass moves along a roughly planar surface with little rotation or backward tilting
    slope_type
    a classification of the slope in which the failure occurred (Source: U.S. Geological Survey and California Geological Survey)
    ValueDefinition
    open slopean area of the continental slope not defined by the boundaries of a submarine canyon and/or channel system
    canyon/channelan area defined by the boundaries of a submarine canyon and/or channel system
    shelfthe area nearest to the coastline characterized by shallow depths and gentle slopes
    shelf edgethe area at the seaward extent of the continental shelf where slopes increase and transition to the continental slope; also referred to as a shelf break
    sed_age
    geologic age of sediment for the majority of the failure area, from literature. See the sedage_ref attribute and the accompanying ReferencesCited_offshore_socal_2023.pdf file in the Attached Files section (https://www.sciencebase.gov/catalog/item/5d9bc778e4b0366162923190) for a comprehensive list of sources used (Source: U.S. Geological Survey)
    ValueDefinition
    Late Cretaceousan age of 65.5-99.6 Ma
    Eocenean age of 55.8-33.9 Ma
    Miocenean age of 23.03-5.33 Ma
    Late Miocenean age of 11.63-5.33 Ma
    Early Pliocenean age of 5.33-3.60 Ma
    Pliocenean age of 5.33-2.59 Ma
    Quaternaryan age of 2.58 Ma-Present
    Pleistocenean age of 2.58 Ma-11.7 ka
    late Pleistocenean age of 129.0-11.7 ka
    Holocenean age of 11.7 ka-Present
    sedage_ref
    citation information for the sed_age attribute (Source: U.S. Geological Survey and California Geological Survey) Source citations used to characterize the age of the failed sediment in the sed_age attribute. See the accompanying ReferencesCited_offshore_socal_2023.pdf file in the Attached Files section (https://www.sciencebase.gov/catalog/item/5d9bc778e4b0366162923190) for a comprehensive list of sources used.
    fail_ageBP
    minimum age of failure in years before present, from literature. Where no fail age data are available, value is 0. See the fl_age_ref attribute and the accompanying ReferencesCited_offshore_socal_2023.pdf file in the Attached Files section (https://www.sciencebase.gov/catalog/item/5d9bc778e4b0366162923190 for a comprehensive list of sources used. (Source: U.S. Geological Survey)
    Range of values
    Minimum:0
    Maximum:200000
    Units:years
    Resolution:1
    fl_age_ref
    citation information for fault strand geometry and attributes. n/a indicates no failure age or reference available. (Source: U.S. Geological Survey and California Geological Survey) Source citations used to characterize the failure age in years before present. See the accompanying ReferencesCited_offshore_socal_2023.pdf file in the Attached Files section (https://www.sciencebase.gov/catalog/item/5d9bc778e4b0366162923190) for a comprehensive list of sources used.
    Entity_and_Attribute_Overview:
    Polygon shapefile containing outlines and attributes of landslides offshore of Southern California
    Entity_and_Attribute_Detail_Citation: U.S. Geological Survey

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Antoinette G. Papesh
    • Maureen L. Walton
    • James E. Conrad
    • Daniel S. Brothers
    • Jared W. Kluesner
    • Mary L. McGann
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    Attn: PCMSC Science Data Coordinator
    2885 Mission Street
    Santa Cruz, CA

    831-427-4747 (voice)
    pcmsc_data@usgs.gov

Why was the data set created?

These data were compiled as a part of a USGS effort to understand the geologic processes of mass wasting offshore of Southern California. They are intended to provide baseline knowledge of the geology, geomorphology, and distribution of discrete landslides offshore of Southern California, for use by scientists, managers, and the general public. These data can be used with (GIS) software for research purposes.

How was the data set created?

  1. From what previous works were the data drawn?
    Dartnell and others, 2015 (source 1 of 7)
    Dartnell, Peter, Driscoll, Neal W., Brothers, Daniel S., Conrad, James E., Kluesner, Jared, Kent, Graham, and Andrews, Brian D., 2015, Colored shaded-relief bathymetry, acoustic backscatter, and selected perspective views of the inner continental borderland, southern California: Scientific Investigations Map DOI:10.3133/sim3324, U.S. Geological Survey, Reston, VA.

    Online Links:

    Type_of_Source_Media: Digital Resource
    Source_Contribution:
    High resolution multibeam bathymetry was used as a base layer to begin drawing polygons for landslide interpretation. This source is a compilation of new and publicly available multibeam bathymetry data gridded at 25-meter resolution. Links to the data sources used are in the Data Catalog of the report.
    Dartnell and others, 2021 (source 2 of 7)
    Dartnell, Peter, Roland, Emily C., Raineault, Nicole A., Castillo, Christopher M., Conrad, James E., Kane, Renato, Brothers, Daniel S., Kluesner, Jared W., and Maureen A. L. Walton, 2021, Colored shaded-relief bathymetry, acoustic backscatter, and selected perspective views of the northern part of the California Continental Borderland, southern California: Scientific Investigations Map DOI:10.3133/sim3473, U.S. Geological Survey, Reston, VA.

    Online Links:

    Type_of_Source_Media: Digital resource
    Source_Contribution:
    High resolution multibeam bathymetry was used as a base layer to begin drawing polygons for landslide interpretation. This is a compilation of publicly available multibeam bathymetry data published at various resolutions ranging from 2-30 meters. Data sources used are shown on Figure 1 of the report and links to the data are provided therein.
    Seafloor Mapping Lab, 2018 (source 3 of 7)
    Seafloor Mapping Lab of California State University Monterey Bay, 2018, California Margin Geology Series: California State University, Monterey Bay, Seaside, CA.

    Online Links:

    Type_of_Source_Media: Digital resource
    Source_Contribution:
    High resolution multibeam bathymetry was used as a base layer to begin drawing polygons for landslide interpretation. High resolution multibeam bathymetry data at resolutions ranging from 2 – 10 meters from survey datasets H11875, H11876, H11877, H11878, H11879, H11880, H11881, H11882, H11883, H11891, H11950, H11951, H11952, H11953, and the 2014 Southern California Data Gap Project (Dana Point, San Onofre Blocks 01-03, La Jolla, Mission Beach, Point Loma North, Point Loma South, and Imperial Beach) were used.
    MBARI Seafloor Mapping Team, 2001 (source 4 of 7)
    Mapping, MBARI Seafloor Team, 2001, Santa Barbara multibeam survey: MBARI, online.

    Online Links:

    Type_of_Source_Media: Digital resource
    Source_Contribution:
    High resolution multibeam bathymetry was used as a base layer to begin drawing polygons for landslide interpretation. This is 20-meter resolution bathymetry data.
    National Geophysical Data Center, 2012 (source 5 of 7)
    NOAA, 2012, U.S. Coastal Relief Model - Southern California vers. 2: NOAA, online.

    Online Links:

    Type_of_Source_Media: Digital resource
    Source_Contribution:
    The NCEI 3-arc-second elevation grid (approximately 90-meter resolution) was used as a base layer to begin drawing polygons for landslide interpretation where no high resolution multibeam bathymetry data (listed above) were available.
    Sliter and others, 2017a (source 6 of 7)
    Sliter, Ray W., Conrad, James E., Ryan, Holly F., and Triezenberg, Peter J., 2017, Minisparker seismic-reflection data of field activity S-12-10-SC: Oceanside to La Jolla, offshore southern California from 2010-06-01 to 2010-06-12: Data Release DOI:10.5066/F7QN64W8, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.

    Online Links:

    Type_of_Source_Media: Digital resource
    Source_Contribution:
    Seismic reflection profiles were used to map extent of debris apron for the Del Mar slide.
    Sliter and others, 2017b (source 7 of 7)
    Sliter, Ray W., Conrad, James E., Ryan, Holly F., and Triezenberg, Peter J., 2017, Minisparker seismic-reflection data of field activity S-07-11-SC: offshore San Diego, and Los Angeles Counties, southern California from 2011-06-08 to 2011-06-22: Data Release DOI:10.5066/F7SF2TCV, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.

    Online Links:

    Type_of_Source_Media: Digital resource
    Source_Contribution:
    Seismic reflection profiles were used to map extent of debris apron for the San Gabriel Slide Complex.
  2. How were the data generated, processed, and modified?
    Date: 02-Feb-2023 (process 1 of 1)
    A compilation of existing bathymetry data was used as a base layer to map landslide features. Data from listed sources was downsampled in ESRI ArcMap and merged into a single 30-m grid to create the base layer. In some cases, the source swath data was higher resolution than the 30-m compilation and was used to map landslide features. A list of source swath data is detailed in the Source Used Citations. Where high (<30 m) resolution data was unavailable, the 90-m resolution NOAA Coastal Relief Model was used as the base layer. Using this base layer, landslides, headwall scarps, and areas of mass-wasting were mapped. Mapped landslide bodies were divided into evacuation zones and debris aprons based on negative (i.e., evacuation zones) or positive (i.e., debris aprons) seafloor relief associated with the landslide masses. Data sources used in this process:
    • Dartnell and others, 2015
    • Dartnell and others, 2021
    • Seafloor Mapping Lab, 2018
    • MBARI Seafloor Mapping Team, 2001
    • National Geophysical Data Center, 2012
    • Sliter and others, 2017a
    • Sliter and others, 2017b
  3. What similar or related data should the user be aware of?

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

  1. How well have the observations been checked?
    No formal attribute accuracy tests were conducted. See the sedage_ref and fl_age_ref attributes within the shapefile, and the accompanying ReferencesCited_offshore_socal_2023.pdf in the Attached Files section (https://www.sciencebase.gov/catalog/item/5d9bc778e4b0366162923190), for details on where to find accuracy information regarding the data reported in the sed_age and fail_ageBP attributes.
  2. How accurate are the geographic locations?
    These data and associated attributes have been created from several bathymetric datasets. Landslide mapping was cross-checked where more than one bathymetric dataset spanned a suspected landslide. The accuracy of landslide mapping correlates to the highest resolution dataset that spans a particular landslide.
  3. How accurate are the heights or depths?
    A formal accuracy assessment of the horizontal positional information in the data set has not been conducted.
  4. Where are the gaps in the data? What is missing?
    Dataset is considered complete for the information presented, as described in the abstract.
  5. How consistent are the relationships among the observations, including topology?
    No formal logical accuracy tests were conducted.

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 USGS-authored or produced data and information are in the public domain from the U.S. Government and are freely redistributable with proper metadata and source attribution. Please recognize and acknowledge the U.S. Geological Survey as the originator(s) of the dataset and in products derived from these data.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - ScienceBase
    Denver Federal Center, Building 810, Mail Stop 302
    Denver, CO

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? landslides_offshore_socal_2023.zip contains the shapefile and associated files, and is accompanied by a browse image and CSDGM FGDC-compliant metadata.
  3. What legal disclaimers am I supposed to read?
    Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty.
  4. How can I download or order the data?
  5. What hardware or software do I need in order to use the data set?
    These data can be viewed with GIS software.

Who wrote the metadata?

Dates:
Last modified: 21-Aug-2023
Metadata author:
U.S. Geological Survey, Pacific Coastal and Marine Science Center
Attn: PCMSC Science Data Coordinator
2885 Mission Street
Santa Cruz, CA

831-427-4747 (voice)
pcmsc_data@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/pcmsc/DataReleases/ScienceBase/DR_P9IIWTYL/landslides_offshore_socal_2023_metadata.faq.html>
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