Metadata: Identification_Information: Citation: Citation_Information: Originator: Geoffrey Phelps Publication_Date: 20020930 Title: Preliminary gravity inversion model of Frenchman Flat basin, Nevada Test Site, Nevada Geospatial_Data_Presentation_Form: raster digital data in ASCII XYZ format Series_Information: Series_Name: U.S. Geological Survey Open-File Report Issue_Identification: 02-363 Publication_Information: Publication_Place: Menlo Park, CA Publisher: U.S. Geological Survey Online_Linkage: http://pubs.usgs.gov/of/2002/0363/ Description: Abstract: The depth of the basin beneath Frenchman Flat is estimated using a gravity inversion method. This dataset is distributed as an XYZ ASCII format data file generated from the 2002 gravity inversion model of the bedrock beneath Frenchman Flat basin. Data forms a rectangular grid of data values in the defined projection. The data values are the depth below the land surface,in meters, of the modeled location of the Pre-Tertiary basement surface. The report which accompanies the data explains the modeling process and results. Purpose: These data are intended for science researchers, students, policy makers, and the general public. The data can be used with geographic information systems (GIS) or other software to display a geophysical model of the elevation of the basin beneath Frenchman Flat, Nevada Test Site, Nevada. Time_Period_of_Content: Time_Period_Information: Single_Date/Time: Calendar_Date: 2002 Currentness_Reference: ground condition Status: Progress: Complete Maintenance_and_Update_Frequency: None planned Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: -116.08897159 East_Bounding_Coordinate: -115.81127475 North_Bounding_Coordinate: 36.93573514 South_Bounding_Coordinate: 36.71733292 Keywords: Theme: Theme_Keyword_Thesaurus: USGS Thesaurus Theme_Keyword: gravitational field (earth) Theme_Keyword: mathematical modeling Theme_Keyword: geospatial datasets Theme: Theme_Keyword_Thesaurus: none Theme_Keyword: gravity Theme_Keyword: inversion Theme_Keyword: basement Theme_Keyword: basin model Theme_Keyword: sensitivity analysis Theme: Theme_Keyword_Thesaurus: ISO 19115 Topic Categories Theme_Keyword: geoscientificInformation Place: Place_Keyword_Thesaurus: none Place_Keyword: Nevada Test Site Place_Keyword: NTS Place_Keyword: Nye County Place_Keyword: Frenchman Flat Place_Keyword: Frenchman Playa Place_Keyword: Nevada Place_Keyword: NV Place_Keyword: USA Place: Place_Keyword_Thesaurus: Augmented FIPS 10-4 and FIPS 6-4 Place_Keyword: f32023 = Nye Access_Constraints: none Use_Constraints: Please recognize the U.S. Geological Survey (USGS) as the source of this information. USGS-authored or produced data and information are in the public domain. Point_of_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Geoffrey Phelps Contact_Organization: U.S. Geological Survey (USGS) Western Earth Surface Processes Team (WESP) Contact_Position: Geologist Contact_Address: Address_Type: mailing and physical address Address: 345 Middlefield Road, MS 989 City: Menlo Park State_or_Province: CA Postal_Code: 94025 Country: USA Contact_Voice_Telephone: 650-329-4922 Contact_Facsimile_Telephone: 650-329-5133 Contact_Electronic_Mail_Address: gphelps@usgs.gov Browse_Graphic: Browse_Graphic_File_Name: http://pubs.usgs.gov/of/2002/0363/pdf/of02-363plate1.pdf Browse_Graphic_File_Description: Printable version of the colorized model, 1.6 megabytes Browse_Graphic_File_Type: PDF Native_Data_Set_Environment: Microsoft Windows 2000 Version 5.0 (Build 2195) Service Pack 1; ESRI ArcCatalog 8.1.1.649 Data_Quality_Information: Attribute_Accuracy: Attribute_Accuracy_Report: The accuracy of the calculation of depth to pre-Cenozoic rock is dependent on many factors, including: the accuracy of the gravity measurements, the relative spacing of the measurements on the ground, the accuracy of the constraints and assumptions built into the reduction process (e.g. assuming an average crustal density of 2670 kg/m3 for complete Bouguer and isostatic corrections), the assumption of uniformly dense, horizontal layers, the density constraints used in the inversion, and the interpolation algorithm used between the data points. The primary source of uncertainty is the density-depth function used to calculate the thickness of the basin fill. To investigate the variation in the final model a sensitivity analysis (Hill, 1998) was performed. The model was perturbed systematically, and 1% scaled sensitivities were calculated for each model parameter (layer). The sensitivities represent the approximate change in depth resulting from a 1% change in the parameter (density) value. We can use them to gain insight into how the parameters quantitatively contribute to the model. However, the sensitivities do not scale; in other words, multiplying one result by 10 does not yield the exact amount the depth would change given a 10 percent change in density. This is because the model is non-linear, and so the values are valid only within a short range of the solution. Figures 8-11 show the 1% scaled sensitivities for the final model in Frenchman Flat. The largest range in sensitivity, indicating the largest overall influence on the model, occurs in the second layer, while the fourth layer has the greatest influence over the deepest part of the basin. Laterally the shallower layers of the model have a greater affect than the deeper layers. The deeper layers influence the deep part of the basin only; this follows from the simple fact that a layer cannot affect the model if the predicted depth is not deep enough to include the layer. The general range of the sensitivity values is from a few meters up to 30 meters. This implies the model is fairly sensitive to density changes, since fluctuations of a few percent imply tens of meters fluctuation in the depth estimates. Logical_Consistency_Report: Values within the raster dataset are valid depth values. Values represent the center of cells 500 meters by 500 meters. From the original rectangular raster dataset, only values with valid depths are present in the ASCII data file (all null values have been omitted). Lineage: Process_Step: Process_Description: The depth to the Pre-Tertiary basement was determined by conducting a gravity inversion modeling process described in the U.S. Geological Survey Open-File report 02-363. The gridded data are converted to an XYZ ASCII format file (northing, easting, depth below surface in meters). Process_Date: 20020930 Process_Step: Process_Description: Creation of original metadata record Process_Date: 20030826 Process_Contact: Contact_Information: Contact_Organization_Primary: Contact_Organization: U.S. Geological Survey (USGS) Western Earth Surface Processes Team (WESP) Contact_Person: Geoffrey Phelps Contact_Position: geologist Contact_Address: Address_Type: mailing and physical address Address: USGS, MailStop 989, 345 Middlefield Road City: Menlo Park State_or_Province: CA Postal_Code: 94025 Contact_Voice_Telephone: 650-329-4922 Spatial_Data_Organization_Information: Direct_Spatial_Reference_Method: Raster Raster_Object_Information: Raster_Object_Type: Grid Cell Row_Count: 49 Column_Count: 49 Vertical_Count: 1 Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: Planar: Grid_Coordinate_System: Grid_Coordinate_System_Name: Universal Transverse Mercator Universal_Transverse_Mercator: UTM_Zone_Number: 11 Transverse_Mercator: Scale_Factor_at_Central_Meridian: 0.9996 Longitude_of_Central_Meridian: -117.0 Latitude_of_Projection_Origin: 0.0 False_Easting: 500000.0 False_Northing: 0.0 Planar_Coordinate_Information: Planar_Coordinate_Encoding_Method: row and column Coordinate_Representation: Abscissa_Resolution: 500.0 Ordinate_Resolution: 500.0 Planar_Distance_Units: meters Geodetic_Model: Horizontal_Datum_Name: North American Datum of 1927 Ellipsoid_Name: Clarke 1866 Semi-major_Axis: 6378206.400000 Denominator_of_Flattening_Ratio: 294.978698 Entity_and_Attribute_Information: Overview_Description: Entity_and_Attribute_Overview: XYZ ASCII file of modeled depth to Pre-Tertiary basement formatted as single lines of text of northing,easting,depth (in meters below ground surface) For example: >596611.73883294,4087950.2778684,0 >597111.73883294,4087950.2778684,0 >597611.73883294,4087950.2778684,0 >595111.73883294,4087450.2778684,711.5488 >595611.73883294,4087450.2778684,639.9702 >596111.73883294,4087450.2778684,236.1196 >596611.73883294,4087450.2778684,0 >597111.73883294,4087450.2778684,0 >597611.73883294,4087450.2778684,6.930904 Entity_and_Attribute_Detail_Citation: http://pubs.usgs.gov/of/2002/0363/pdf/of02-363.pdf Distribution_Information: Distributor: Contact_Information: Contact_Organization_Primary: Contact_Organization: United States Geological Survey (USGS) Information Services Contact_Address: Address_Type: mailing and physical address Address: Box 25286 City: Denver State_or_Province: CO Postal_Code: 80225 Country: USA Contact_Voice_Telephone: (888)ASK-USGS Resource_Description: USGS Open-File Report 02-363 Distribution_Liability: Although these data have been used by the U.S. Geological Survey, U.S. Department of the Interior, these data and information are provided with the understanding that they are not guaranteed to be usable, timely, accurate, or complete. Users are cautioned to consider carefully the provisional nature of these data and information before using them for decisions that concern personal or public safety or the conduct of business that involves substantial monetary or operational consequences. Conclusions drawn from, or actions undertaken on the basis of, such data and information are the sole responsibility of the user. Neither the U.S. Government nor any agency thereof, 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 data, software, information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. Trade, firm, or product names and other references to non-USGS products and services are provided for information only and do not constitute endorsement or warranty, express or implied, by the USGS, USDOI, or U.S. Government, as to their suitability, content, usefulness, functioning, completeness, or accuracy. Standard_Order_Process: Digital_Form: Digital_Transfer_Information: Format_Name: Columnar text Format_Specification: comma-separated values, one point location per line Format_Version_Date: 20020930 Format_Information_Content: x-coordinate, y-coordinate, depth in meters below ground surface File_Decompression_Technique: none Transfer_Size: 0.0654 Digital_Transfer_Option: Online_Option: Computer_Contact_Information: Network_Address: Network_Resource_Name: http://pubs.usgs.gov/of/2002/0363/of02-363depthdata.asc Fees: none Metadata_Reference_Information: Metadata_Date: 20160613 Metadata_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Peter N Schweitzer Contact_Organization: USGS Midwest Area Contact_Position: Collection manager, USGS Geoscience Data Clearinghouse, http://geo-nsdi.er.usgs.gov/ Contact_Address: Address_Type: mailing address Address: Mail Stop 954 12201 Sunrise Valley Dr City: Reston State_or_Province: VA Postal_Code: 20192-0002 Country: USA Contact_Voice_Telephone: 703-648-6533 Contact_Facsimile_Telephone: 703-648-6252 Contact_Electronic_Mail_Address: pschweitzer@usgs.gov Metadata_Standard_Name: Content Standard for Digital Geospatial Metadata Metadata_Standard_Version: FGDC-STD-001-1998