Earthquake Hazards Program

U.S. Geological Survey
Data Series 91
Version 1.2.

Depth to the Juan De Fuca Slab Beneath the Cascadia Subduction Margin–A 3-D Model for Sorting Earthquakes

By Patricia A. McCrory, J. Luke Blair, David H. Oppenheimer, and Stephen R. Walter


map of on-and off-shore northwest Washington state showing earthquake epicenters
Map showing seismicity within North American plate, above slab surface (from figure 7)

We present an updated model of the Juan de Fuca slab beneath southern British Columbia, Washington, Oregon, and northern California, and use this model to separate earthquakes occurring above and below the slab surface. The model is based on depth contours previously published by Flück and others (1997). Our model attempts to rectify a number of shortcomings in the original model and to update it with new work. The most significant improvements include (1) a gridded slab surface in geo-referenced (ArcGIS) format, (2) continuation of the slab surface to its full northern and southern edges, (3) extension of the slab surface from 50-km depth down to 110-km beneath the Cascade arc volcanoes, and (4) revision of the slab shape based on new seismic-reflection and seismic-refraction studies. We have used this surface to sort earthquakes and present some general observations and interpretations of seismicity patterns revealed by our analysis. In addition, we provide files of earthquakes above and below the slab surface and a 3-D animation or fly-through showing a shaded-relief map with plate boundaries, the slab surface, and hypocenters for use as a visualization tool.

Readme text (1_README.pdf; 56 KB)

Main text of this publication (2_TEXT.pdf; 224 KB with links to 54 MB of illustrations)

Go to the 3_FIGURES folder containing the figures for this report as PDF files as well as a set of small JPG files of the same illustrations. (18 items that total 54.7 MB)

Go to the 4_DATA folder containing GIS data, metadata, and animations. (16 items that total 117.2 MB)

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For questions about the content of this report, contact Pat McCrory

Version history (version_history.pdf; 32 KB)

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