Antoinette G. Papesh Maureen L. Walton James E. Conrad Daniel S. Brothers Jared W. Kluesner Mary L. McGann 20230821 polygon shapefile data release DOI:10.5066/P9IIWTYL Pacific Coastal and Marine Science Center, Santa Cruz, CA U.S. Geological Survey https://doi.org/10.5066/P9IIWTYL https://www.sciencebase.gov/catalog/item/5ef129ec82ced62aaae18f59 Antoinette G. Papesh Maureen L. Walton James E. Conrad Daniel S. Brothers Jared W. Kluesner Mary L. McGann 2023 data release DOI:10.5066/P9IIWTYL Pacific Coastal and Marine Science Center, Santa Cruz, CA U.S. Geological Survey https://doi.org/10.5066/P9IIWTYL 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. 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. 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. 1998 20210730 ground condition Complete None planned -120.913005 -117.311194 34.518320 32.425737 ISO 19115 Topic Category geoscientificInformation oceans Data Categories for Marine Planning Distributions USGS Thesaurus scientific interpretation geospatial datasets earth characteristics sea-floor characteristics marine geophysics marine geology landslides hazards geologic processes oceanic lithosphere Marine Realms Information Bank (MRIB) keywords natural agents of coastal change geology geophysics geological features hazards and disasters earthquake effects geologic mapping oceanographic observations None U.S. Geological Survey USGS Coastal and Marine Hazards and Resources Program CMHRP Pacific Coastal and Marine Science Center PCMSC USGS Metadata Identifier USGS:5ef129ec82ced62aaae18f59 Geographic Names Information System (GNIS) United States of America State of California Pacific Ocean None 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. U.S. Geological Survey, Pacific Coastal and Marine Science Center PCMSC Science Data Coordinator mailing and physical

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Santa Cruz CA 95060 831-427-4747 pcmsc_data@usgs.gov landslides_offshore_socal_2023_thumb.png Southern California location map with bathymetry and mapped discrete landslides PNG Mac Pro, Late 2013, with macOS High Sierra, version 10.13.6 running Parallels Virtual Machine; ESRI ArcGIS 10.7. 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. No formal logical accuracy tests were conducted. Dataset is considered complete for the information presented, as described in the abstract. 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. A formal accuracy assessment of the horizontal positional information in the data set has not been conducted. Peter Dartnell Neal W. Driscoll Daniel S. Brothers James E. Conrad Jared Kluesner Graham Kent Brian D. Andrews 2015 Raster Digital Data Set Scientific Investigations Map DOI:10.3133/sim3324 Reston, VA U.S. Geological Survey https://doi.org/10.3133/sim3324 Digital Resource 1998 2014 ground condition Dartnell and others, 2015 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. Peter Dartnell Emily C. Roland Nicole A. Raineault Christopher M. Castillo James E. Conrad Renato Kane Daniel S. Brothers Jared W. Kluesner Maureen A. L. Walton 2021 Raster Digital Data Set Scientific Investigations Map DOI:10.3133/sim3473 Reston, VA U.S. Geological Survey https://doi.org/10.3133/sim3473 Digital resource 1998 2018 ground condition Dartnell and others, 2021 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 of California State University Monterey Bay 2018 Raster Digital Data Sets Seaside, CA California State University, Monterey Bay http://seafloor.otterlabs.org/SFMLwebDATA.htm Digital resource 2000 2018 ground condition Seafloor Mapping Lab, 2018 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 Raster Digital Data Set online MBARI https://www3.mbari.org/data/mapping/Santa_Barbara_Basin/ Digital resource 1998 2001 ground condition MBARI Seafloor Mapping Team, 2001 High resolution multibeam bathymetry was used as a base layer to begin drawing polygons for landslide interpretation. This is 20-meter resolution bathymetry data. NOAA 2012 Raster Digital Data Sets online NOAA https://doi.org/10.7289/V5V985ZM Digital resource 19990101 Present published 2013-07-08 National Geophysical Data Center, 2012 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. Ray W. Sliter James E. Conrad Holly F. Ryan Peter J. Triezenberg 2017 seismic-reflection data in SEG-Y format Data Release DOI:10.5066/F7QN64W8 Pacific Coastal and Marine Science Center, Santa Cruz, CA U.S. Geological Survey https://doi.org/10.5066/F7QN64W8 https://cmgds.marine.usgs.gov/data-releases/datarelease/10.5066-F7QN64W8/ Digital resource 20100601 20100612 ground condition Sliter and others, 2017a Seismic reflection profiles were used to map extent of debris apron for the Del Mar slide. Ray W. Sliter James E. Conrad Holly F. Ryan Peter J. Triezenberg 2017 seismic-reflection data in SEG-Y format Data Release DOI:10.5066/F7SF2TCV Pacific Coastal and Marine Science Center, Santa Cruz, CA U.S. Geological Survey https://doi.org/10.5066/F7SF2TCV https://cmgds.marine.usgs.gov/data-releases/datarelease/10.5066-F7SF2TCV/ Digital resource 20110608 20110622 ground condition Sliter and others, 2017b Seismic reflection profiles were used to map extent of debris apron for the San Gabriel Slide Complex. 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. 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 20230202 Vector GT-polygon composed of chains 63 0.0001 0.0001 Decimal degrees D_WGS_1984 WGS_1984 6378137.0 298.257223563 North American Vertical Datum of 1988 1.0 meters Explicit depth coordinate included with horizontal coordinates landslides_offshore_socal_2023 polygons representing mapped landslides U.S. Geological Survey FID internal feature number Esri automatically generated sequential unique whole number identifier Shape feature geometry Esri feature type name_id the name of the landslide 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 U.S. Geological Survey and California Geological Survey The commonly reported geographic location of the landslide lat_dd centroid coordinate latitude Esri 32.48469 34.50649 degrees 0.000001 long_dd centroid coordinate longitude Esri -120.808261 -117.374616 degrees 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. Esri 25646 232290744 square meters 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. U.S. Geological Survey 11377 2699725 square meters 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 U.S. Geological Survey 204 32616 meters 1 scarp_ht_m a hand measurement of the landslide headwall scarp height in meters; see the scp_ht_err attribute for uncertainty Esri 1 200 meters 1 scp_ht_err estimated uncertainty of the landslide headwall scarp height measurement, see scarp_ht_m, in meters Esri 1 40 meters 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. U.S. Geological Survey 23847 8854292904 cubic meters 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. U.S. Geological Survey 14 108 percent 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 U.S. Geological Survey and California Geological Survey 0.6 36.8 degrees 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 U.S. Geological Survey and California Geological Survey 0 4.4 degrees 0.1 grad_pct gradient percentage calculated from the slope_deg attribute value using tan (slope_deg)*100; values reported as percentage U.S. Geological Survey and California Geological Survey 1 75 percent 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 Esri 9 1409 meters 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 Esri 49 2619 meters 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) Esri 0 44165 meters 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) Esri 0 29002 meters 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 Esri 0 48340 meters 1 data_type a list of primary data types used for landslide mapping, categorized as bathymetry (with resolution in parentheses), seismic reflection 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 U.S. Geological Survey debris avalanche source areas often associated with steep gullies and usually indicated by the presence of a debris field containing blocky material, often indicating rapid debris flow. U.S. Geological Survey earth flow a slide consisting of unconsolidated surficial material, typically with a characteristic hourglass geometry U.S. Geological Survey rotational a 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 U.S. Geological Survey translational a slide in which mass moves along a roughly planar surface with little rotation or backward tilting U.S. Geological Survey slope_type a classification of the slope in which the failure occurred U.S. Geological Survey and California Geological Survey open slope an area of the continental slope not defined by the boundaries of a submarine canyon and/or channel system U.S. Geological Survey and California Geological Survey canyon/channel an area defined by the boundaries of a submarine canyon and/or channel system U.S. Geological Survey and California Geological Survey shelf the area nearest to the coastline characterized by shallow depths and gentle slopes U.S. Geological Survey and California Geological Survey shelf edge the 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 U.S. Geological Survey and California Geological Survey 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 U.S. Geological Survey Late Cretaceous an age of 65.5-99.6 Ma USGS, 2010; Cohen and others, 2023 Eocene an age of 55.8-33.9 Ma USGS, 2010; Cohen and others, 2023 Miocene an age of 23.03-5.33 Ma USGS, 2010; Cohen and others, 2023 Late Miocene an age of 11.63-5.33 Ma USGS, 2010; Cohen and others, 2023 Early Pliocene an age of 5.33-3.60 Ma USGS, 2010; Cohen and others, 2023 Pliocene an age of 5.33-2.59 Ma USGS, 2010; Cohen and others, 2023 Quaternary an age of 2.58 Ma-Present USGS, 2010; Cohen and others, 2023 Pleistocene an age of 2.58 Ma-11.7 ka USGS, 2010; Cohen and others, 2023 late Pleistocene an age of 129.0-11.7 ka USGS, 2010; Cohen and others, 2023 Holocene an age of 11.7 ka-Present USGS, 2010; Cohen and others, 2023 sedage_ref citation information for the sed_age attribute 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. U.S. Geological Survey 0 200000 years 1 fl_age_ref citation information for fault strand geometry and attributes. n/a indicates no failure age or reference available. 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. Polygon shapefile containing outlines and attributes of landslides offshore of Southern California U.S. Geological Survey U.S. Geological Survey - ScienceBase Mailing and Physical

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Denver CO 80225 1-888-275-8747 sciencebase@usgs.gov landslides_offshore_socal_2023.zip contains the shapefile and associated files, and is accompanied by a browse image and CSDGM FGDC-compliant metadata. 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. Shapefile ArcGIS 10.7 polygon shapefile Zip file contains the interpreted polygons shapefile, associated files, a browse image, and the metadata Winzip, 7-zip, or Winrar are free software that will open .zip files. 1.8 https://www.sciencebase.gov/catalog/file/get/5ef129ec82ced62aaae18f59 https://www.sciencebase.gov/catalog/item/5ef129ec82ced62aaae18f59 https://doi.org/10.5066/P9IIWTYL Data can be downloaded using the Network_Resource_Name links. The first link is a direct link to download the zipped file of data and metadata. The second link points to a landing page with metadata and data. The third link points to the landing page for the entire data release. None. These data can be viewed with GIS software. 20230821 U.S. Geological Survey, Pacific Coastal and Marine Science Center PCMSC Science Data Coordinator mailing and physical

2885 Mission Street

Santa Cruz CA 95060 831-427-4747 pcmsc_data@usgs.gov Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998