Identification_Information: Citation: Citation_Information: Originator: R.J. Wooley, R.F. Yerkes, V.E. Langenheim, and F.C. Chuang Publication_Date: 2003 Title: Isostatic gravity map of the Los Angeles 30 x 60 minute quadrangle, California Edition: rev 1.0 Publication_Information: Publication_Place: U.S. Geological Survey, Menlo Park, CA Publisher: U.S. Geological Survey Online_Linkage: http://wrgis.wr.usgs.gov/open-file/of03-269 Description: Abstract: Gravity data were compiled, collected, and edited to produce an isostatic gravity map of the Los Angeles 30 x 60 minute quadrangle, California. Purpose: To provide basic geophysical information to regional mapping and earthquake studies Point_of_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Victoria E. Langenheim Contact_Organization: U.S. Geological Survey Contact_Address: Address: 345 Middlefield Rd. MS 989 City: Menlo Park State_or_Province: CA Postal_Code: 94025 Country: USA Address_Type: mailing and physical address Contact_Voice_Telephone: 650-329-5313 Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: -119.0 East_Bounding_Coordinate: -118.0 North_Bounding_Coordinate: 34.5 South_Bounding_Coordinate: 34.0 Native_Data_Set_Environment: data was stored and analysed on a SUN Ultra4000 UNIX platform Status: Progress: Preliminary report Maintenance_and_Update_Frequency: none planned Keywords: Place: Place_Keyword: Southern California, Los Angeles, San Gabriel Mountains Theme: Theme_Keyword: gravity, density, isostatic anomaly Access_Constraints: none Use_Constraints: none Data_Quality_Information: Positional_Accuracy: Horizontal_Positional_Accuracy: Horizontal_Positional_Accuracy_Report: Accuracy of the point data is roughly 40 m, as well as the data can be located on a 1:24,000-scale topographic map Vertical_Positional_Accuracy: Vertical_Positional_Accuracy_Report: Accuracy of the point data vary; most of the elevations are accurate to 10 feet or less. In some of the more mountainous areas, the accuracy may fall to 20 to 40 feet. Attribute_Accuracy: Attribute_Accuracy_Report: Observed gravity data are accurate to 0.05 mGal; reduced anomalies are accurate to 1-2 mGal. Data are more accurate in the valleys than in the mountains because of uncertainties in elevation and in the terrain correction. Logical_Consistency_Report: see open-file report Completeness_Report: Dataset based on geophysical analysis. see open-file report. Lineage: Source_Information: Source_Citation: Citation_Information: Originator: Hanna, W.F., Rietman, J.D., and Biehler, S.H. Publication_Date: 1975 Title: Bouguer gravity map of California, Los Angeles sheet Series_Information: Series_Name: California Division of Mines and Geology Edition: first edition Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: Geodetic_Model: Horizontal_Datum_Name: Geographic NAD27 Ellipsoid_Name: CLARKE 1866 Entity_and_Attribute_Information: Detailed_Description: Entity_Type: Entity_Type_Definition: Point_Type Overview_Description: Entity_and_Attribute_Overview: The data file is in ASCII format. The data define point data with information as follows: tem Explanation STAT ..................Station Name--An alphanumeric combination of up to 8 characters used for station identification LaD ...................Degree Latitude North LaM ...................Decimal Minute LoD ...................Degree Longitude West LoM ...................Decimal Minute ELEV ...................Elevation in feet OG .........................Observed gravity, in mGal FAA .......................Free-air anomaly, in mGal SBA ........................Simple Bouguer anomaly, in mGal ITC ........................Inner terrain correction for a density of 2.67 g/cc, in mGal. See Code column for radius of correction. TTC .........................Total terrain correction from the station to 166.7 km for a density of 2.67 g/cc, in mGal. Code .........................Letter denoting the zone (radius) of the correction, "D"= 0.59 km; "G" = 3.52 km; "M"= 58.8 km. CBA ........................Complete Bouguer anomaly reduced for a density of 2.67 g/cc, in mGal. ISO ........................Isostatic residual anomaly,in mGal,assuming an Airy model for isostatic compensation of topographic loads. This model assumes a crustal thickness of 25 km, a topographic load density of 2.67 g/cc, and a density contrast across the base of the model crust of 0.4 g/cc. Isostatic correction would be difference between CBA and ISO values. Overview_Description: Entity_and_Attribute_Overview: point data representing gravity data Metadata_Reference_Information: Metadata_Date: 20021106 Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata