HTML Containing Interpreted and Uninterpreted JPEG Images of Seismic-Reflection Profiles Collected in Lake Mead in 2001

Frequently-anticipated questions:

• What does this data set describe?
  1. How should this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
• Who produced the data set?
  1. Who are the originators of the data set?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• How was the data set created?
  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
  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?
  2. How accurate are the geographic locations?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
  5. How consistent are the relationships among the data, including topology?
• How can someone get a copy of the data set?
  1. Are there legal restrictions on access or use of the data?
  2. Who distributes the data?
  3. What's the catalog number I need to order this data set?
  4. What legal disclaimers am I supposed to read?
  5. How can I download or order the data?
• Who wrote the metadata?

Title:

HTML Containing Interpreted and Uninterpreted JPEG Images of Seismic-Reflection Profiles Collected in Lake Mead in 2001

Abstract:

Lake Mead is a large interstate reservoir located in the Mojave Desert of southeastern Nevada and northwestern Arizona. It was impounded in 1935 by the construction of Hoover Dam and is one of a series of multi-purpose reservoirs on the Colorado River. The lake extends 183 km from the mouth of the Grand Canyon to Black Canyon, the site of Hoover Dam, and provides water for residential, commercial, industrial, recreational, and other non-agricultural users in communities across the southwestern United States. Extensive research has been conducted on Lake Mead, but a majority of the studies have involved determining levels of anthropogenic contaminants such as synthetic organic compounds, heavy metals and dissolved ions, furans/dioxins, and nutrient loading in lake water, sediment, and biota (Preissler, et al., 1998; Bevans et al, 1996; Bevans et al., 1998; Covay and Leiker, 1998; LaBounty and Horn, 1997; Paulson, 1981). By contrast, little work has focused on the sediments in the lake and the processes of deposition (Gould, 1951). To address these questions, sidescan-sonar imagery and high-resolution seismic-reflection profiles were collected throughout Lake Mead by the USGS in cooperation with researchers from University of Nevada Las Vegas (UNLV). These data allow a detailed mapping of the surficial geology and the distribution and thickness of sediment that has accumulated in the lake since the completion of Hoover Dam. Results indicate that the accumulation of post-impoundment sediment is primarily restricted to former river and stream beds that are now submerged below the lake while the margins of the lake appear to be devoid of post-impoundment sediment. The sediment cover along the original Colorado River bed is continuous and is typically greater than 10 m thick through much of its length. Sediment thickness in some areas exceeds 35 m while the smaller tributary valleys typically are filled with less than 4 m of sediment. Away from the river beds that are now covered with post-impoundment sediment, pre-impoundment alluvial deposits and rock outcrops are still exposed on the lake floor.

1. How should this data set be cited?

   Cross, VeeAnn A. , and Twichell, David C. , 2003, HTML Containing Interpreted and Uninterpreted JPEG Images of Seismic-Reflection Profiles Collected in Lake Mead in 2001:, U.S. Geological Survey, Coastal and Marine Geology Team, Woods Hole Field Center, Woods Hole, MA.

   This is part of the following larger work.

   Twichell, David C. , Cross, VeeAnn A. , and Belew, Stephen D. , 2003, Mapping the floor of Lake Mead (Nevada and Arizona): Preliminary discussion and GIS data release: Open-File Report 03-320, U.S. Geological Survey, Woods Hole Field Center, Woods Hole, MA.

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -114.7642

   East_Bounding_Coordinate: -114.0187

   North_Bounding_Coordinate: 36.4871

   South_Bounding_Coordinate: 36.0000

3. What does it look like?

4. Does the data set describe conditions during a particular time period?

   Beginning_Date: 01-Apr-2001

   Ending_Date: 26-Apr-2001

   Currentness_Reference: ground condition

5. What is the general form of this data set?

6. How does the data set represent geographic features?
   1. How are geographic features stored in the data set?

   2. What coordinate system is used to represent geographic features?

7. How does the data set describe geographic features?

   Entity_and_Attribute_Overview:

   These images are intended only as previews of the seismic-reflection data. In each image, the x-axis represents shot point, the y-axis is two-way travel time in milliseconds. The scale bar along the bottom of the image is inaccurate due to a bug in the digital processing software and therefore should be ignored.

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   • VeeAnn A. Cross
   • David C. Twichell

2. Who also contributed to the data set?

3. To whom should users address questions about the data?

   VeeAnn A. Cross
   USGS
   Marine Geologist
   384 Woods Hole Rd.
   Woods Hole, MA 02543-1598
   

   508-548-8700 x2251 (voice)
   508-457-2310 (FAX)
   vatnipp@usgs.gov
   

These images of the seismic-reflection profiles are provided so that individuals can preview the seismic data without the requirement of special software.

1. From what previous works were the data drawn?

2. How were the data generated, processed, and modified?

   (process 1 of 7)

   The seismic data collected in 2001 was actually of 2 types: chirp and boomer. The chirp data was collected as part of the SIS-1000 system, while the boomer data was logged onto a Triton Elics system.

   (process 2 of 7)

   The SEG-Y data was then loaded into Landmark software and interpreted.

   (process 3 of 7)

   CGM images were created of each seismic profile - with the interpretation and without the interpretation. Therefore 2 images for each profile. The interpreted post-impoundment surface is the blue line, while the interpreted pre-impoundment surface is the red line.

   (process 4 of 7)

   These CGM images were converted to JPEGs using Larson software.

   (process 5 of 7)

   These jpegs were then downsampled to a GIF format using djpeg on a UNIX system.

   (process 6 of 7)

   These GIFS were then converted back to JPEGs using the convert command on a UNIX system.

   (process 7 of 7)

   An html document was generated within Dreamweaver for each seismic line to hold both the interpreted and uninterpreted seismic-reflection profiles.

3. What similar or related data should the user be aware of?

   Bevans, H.E., Goodbred, S.L., Miesner, J.F., Watkins, S.A., Gross, T.S., Denslow, N.D., and Choeb, T., 1996, Synthetic organic compounds and carp endrocrinology and histology, Las Vegas Wash and Las Vegas and Callville bays of Lake Mead Nevada: Water-Resources Investigations 96-4266, U.S. Geological Survey.

   Bevans, H.E., Lico, M.S., and Lawrence, S.J., 1998, Water quality in the Las Vegas Valley area and the Carson and Truckee River basins, Nevada and California, 1992-1996: Circular 1170, U.S. Geological Survey.

   Couvay, K.J., and Leiker, T.J., 1998, Synthetic organic compounds in water and bottom sediment from streams, detention basins, and sewage-treatment plant outfalls in Las Vegas Valley, Nevada, 1997: Open-File Report 98-633, U.S. Geological Survey.

   Cross, V.A., and Twichell, D.C., 2003, Archive of Seismic-Reflection Data Collected During USGS Cruise Lake Mead 01007 in Lake Mead - Nevada and Arizona, 1-28 April, 2001: Open-File Report 02-478, U.S. Geological Survey.

   Gould, H.R., 1951, Some quantitative aspects of Lake Mead turbidity currents: SEPM Special Publication No. 2, Society of Economic Paleontologists and Mineralogists.

   LaBounty, J.F., and Horn, M.J., 1997, The influence of drainage from the Las Vegas Valley on the limnology of Boulder Basin, Lake Mead, Arizona-Nevada: Journal of Lake and Reservoir Management v. 13.

   Paulson, L.J., 1981, Nutrient management with hydroelectric dams on the Colorado River: Technical Report #8, Lake Mead Limnological Research Center, Department of Biological Sciences, University of Nevada, Las Vegas, Nevada.

   Preissler, A.M., Roach, G.A., Thomas, K.A., and Wilson, J.W., 1998, Water resources data, Nevada, water year 1998: Water Resources Data Nevada NV-98-1, U.S. Geological Survey.

1. How well have the observations been checked?

2. How accurate are the geographic locations?

3. How accurate are the heights or depths?

4. Where are the gaps in the data? What is missing?

   These files represent images of all the seismic-reflection data collected in Lake Mead in 2001 by the USGS.

5. How consistent are the relationships among the observations, including topology?

Are there legal restrictions on access or use of the data?

Access_Constraints: None

Use_Constraints:

The U.S. Geological Survey must be referenced as the originator of the dataset in any future products or research derived from these data.

1. Who distributes the data set? (Distributor 1 of 1)

   VeeAnn A. Cross
   USGS
   Marine Geologist
   384 Woods Hole Rd.
   Woods Hole, MA 02543-1598
   

   508-548-8700 x2251 (voice)
   508-457-2310 (FAX)
   vatnipp@usgs.gov
   

2. What's the catalog number I need to order this data set?

   Downloadable Data

3. What legal disclaimers am I supposed to read?

   These data were prepared by an agency of the United States Government. Neither the United States government nor any agency thereof, nor any of their employees, make any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed in this report, or represents that its use would not infringe privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. Any views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. Although all data published in this report have been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and related materials and/or the functioning of the software. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of this data, software, or related materials.

4. How can I download or order the data?

Dates:

Last modified: 03-Oct-2003

Metadata author:

VeeAnn A. Cross
USGS
Marine Geologist
384 Woods Hole Rd.
Woods Hole, MA 02543-1598

508-548-8700 x2251 (voice)
508-457-2310 (FAX)
vatnipp@usgs.gov

Metadata standard:

FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

Metadata extensions used:

• <http://www.esri.com/metadata/esriprof80.html>