Cascadia Structure Imaging and Tectonic Modeling

The map above provides background material for a project which involves developing three-dimensional images of the crust and subducting Juan de Fuca plate in western Washington using local earthquake tomography, gravity, aeromagnetic, and magnetotelluric data. You can click on most features of the map to obtain background information, as well as detailed results and interpretations. For instance, clicking on the two red lines will bring up velocity information used in the image construction. Explore the rest of the map; anywhere a hand appears, there is information available with a click of the mouse.

The three-dimensional image construction is being combined with seismicity patterns and other seismicity parameters, geologic information, strain models, and GPS data to provide a tectonic synthesis for the dynamics and earthquake hazards of northern Cascadia. The three-dimensional representation of the subduction zone protrayed in the diagram is based upon subsurface information from seismic reflection and magnetotelluric data, but primarily on new local earthquake tomographic models.

Disclaimer--"Any geologic interpretations implied in the results shown on these web pages are provisional and have not received final approval from USGS administration. Users are cautioned to consider carefully the provisional nature of the information before using it for decisions that concern personal or public safety or the conduct of business that involves substantial monetary or operational consequences."


USGS Open File Report 99-311

Subduction Zone and Crustal Dynamics of Western Washington: a Tectonic Model for Earthquake Hazards Evaluation

By Dal Stanley, Antonio Villasenor, and Harley Benz

65 pages, 64 illustrations

Available at

Project staff:

Dal Stanley:

Harley Benz:

Antonio Villasenor:


All earthquake data used in the velocity modeling and in seismicity studies was obtained from the Pacific Northwest Seismic Network. Most of the maps were made with Generic Mapping Tools (GMT).

 Return to: PACNW | Earthquake Hazards | Central Region | USGS

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Modified April 28, 1999