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Results for “Preliminary Report”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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At least 1,225 records · Page 68Linked to original sources
USGS1991

Maps and cross sections depicting the shallow seismic stratigraphy of the continental shelf and slope off Georgia from interpretation of high-resolution seismic-reflection data

A seismic-stratigraphic study that used existing USGS high-resolution seismic-reflection profiles was made in the area of the TACTS coreholes. This report presents interpreted cross sections and isopach and structure-contour maps that resulted from that study and some preliminary conclusions. Structure contour maps showing depth below sea level to the upper Eocene, Oligocene, lower Miocene, middle Miocene, lower Pliocene, upper Pliocene, and Quaternary strata are presented. Maps that show the thickness of Oligocene, lower and middle Miocene, middle Miocene, lower Pliocene, upper Pliocene, and Quaternary strata and the total sediment thickness above the phosphatic middle Miocene strata are also shown.

Georgia↗
USGS2007

Velocity and Density Models Incorporating the Cascadia Subduction Zone for 3D Earthquake Ground Motion Simulations

In support of earthquake hazards and ground motion studies in the Pacific Northwest, three-dimensional P- and S-wave velocity (3D Vp and Vs) and density (3D rho) models incorporating the Cascadia subduction zone have been developed for the region encompassed from about 40.2°N to 50°N latitude, and from about -122°W to -129°W longitude. The model volume includes elevations from 0 km to 60 km (elevation is opposite of depth in model coordinates). Stephenson and Frankel (2003) presented preliminary ground motion simulations valid up to 0.1 Hz using an earlier version of these models. The version of the model volume described here includes more structural and geophysical detail, particularly in the Puget Lowland as required for scenario earthquake simulations in the development of the Seattle Urban Hazards Maps (Frankel and others, 2007). Olsen and others (in press) used the model volume discussed here to perform a Cascadia simulation up to 0.5 Hz using a Sumatra-Andaman Islands rupture history. As research from the EarthScope Program (http://www.earthscope.org ) is published, a wealth of important detail can be added to these model volumes, particularly to depths of the upper-mantle. However, at the time of development for this model version, no EarthScope-specific results were incorporated. This report is intended to be a reference for colleagues and associates who have used or are planning to use this preliminary model in their research. To this end, it is intended that these models will be considered a beginning template for a community velocity model of the Cascadia region as more data and results become available.

Open-File Report↗