Geophysical Unit of Menlo Park, Calif.

U.S. Geological Survey
Open-File Report 2007-1058
Version 1.0

Principal Facts of Gravity data in the Northern Willamette Valley and Vicinity, Northwestern Oregon and Southwestern Washington

By Robert L. Morin, Karen L. Wheeler, Darcy K. McPhee, Philip A. Dinterman, and Janet T. Watt


thumbnail of map

Gravity data were collected from 2004 through 2006 to assist in mapping subsurface geology in the northern Willamette Valley and vicinity, northwestern Oregon and southwestern Washington. Prior to this effort to improve the gravity data coverage in the study area, very little regional data were available. This report gives the principle facts for 2710 new gravity stations and 1446 preexisting gravity stations. Much of the study area is now covered with data of sufficient density to define basin boundaries and correlate with many of the larger fault systems.

,p> The study area lies between 44° 52.5’ and 46° N latitude and between 122° 15’ and 123° 37.5’ W longitude. Although this is a continuing project and more gravity data is expected to be collected, this report is being published to show the progress of the data collection. The majority of these data are spaced at about 1.6 km (1 mile), but three closely spaced profiles were measured in the Portland area across several faults. To obtain a 1.6 km grid of data points would require about 5120 gravity stations. To date we have collected 2710 stations. Including the preexisting data points, the total number of stations is 4156, and complete regional coverage is about 80 percent at this time.

Download this report as a nine-page PDF file (of2007-1058.pdf; 872 kB).

Download the gravity map as a 24" x 24" PDF file (of2007-1058_gravity-map.pdf; 1.2 MB).

Go to the data folder (11 items that total 25.4 MB). This folder contains the gravity data and the base-station descriptions. The files are described in the nine-page report linked above.

For questions about the content of this report, contact Bob Morin

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